Replace many uses of String::format with more type-safe alternatives
https://bugs.webkit.org/show_bug.cgi?id=192742

Reviewed by Mark Lam.

Source/JavaScriptCore:

* inspector/InjectedScriptBase.cpp:
(Inspector::InjectedScriptBase::makeCall): Use makeString.
(Inspector::InjectedScriptBase::makeAsyncCall): Ditto.
* inspector/InspectorBackendDispatcher.cpp:
(Inspector::BackendDispatcher::getPropertyValue): Ditto.
* inspector/agents/InspectorConsoleAgent.cpp:
(Inspector::InspectorConsoleAgent::enable): Ditto.
* jsc.cpp:
(FunctionJSCStackFunctor::operator() const): Ditto.

* runtime/CodeCache.cpp:
(JSC::writeCodeBlock): Use makeString's numeric capabilities instead of
using String::number.

* runtime/IntlDateTimeFormat.cpp:
(JSC::IntlDateTimeFormat::initializeDateTimeFormat): Use string concatenation.
* runtime/IntlObject.cpp:
(JSC::canonicalizeLocaleList): Ditto.

Source/WebCore:

A while back, String::format was more efficient than string concatenation,
but that is no longer true, and we should prefer String::number, makeString,
or concatenation with the "+" operator to String::format for new code.

This is not as good for programmers who are fond of printf formatting
style, and in some cases it's a little harder to read the strings
interspersed with variables rather than a format string, but it's better
in a few ways:

- more efficient (I didn't measure the difference, but it's definitely
  slower to use String::Format which calls vsnprintf twice than to use
  the WTF code)
- works in a type-safe way without a need to use a format specifier such
  as "%" PRIu64 or "%tu" making it much easier to avoid problems due to
  subtle differences between platforms
- allows us to use StringView in some cases to sidestep the need to
  allocate temporary WTF::String objects
- does not require converting each WTF::String to a C string, allowing
  us to remove many cases of ".utf8().data()" and similar expressions,
  eliminating the allocation of temporary WTF::CString objects

This patch covers a batch of easiest-to-convert call sites.
Later patches will allow us to deprecate or remove String::format.

* Modules/indexeddb/server/SQLiteIDBBackingStore.cpp:
(WebCore::IDBServer::SQLiteIDBBackingStore::addRecord): Use makeString.
* Modules/indexeddb/shared/IDBCursorInfo.cpp:
(WebCore::IDBCursorInfo::loggingString const): Ditto.
* Modules/indexeddb/shared/IDBGetAllRecordsData.cpp:
(WebCore::IDBGetAllRecordsData::loggingString const): Ditto.
* Modules/indexeddb/shared/IDBGetRecordData.cpp:
(WebCore::IDBGetRecordData::loggingString const): Ditto.
* Modules/indexeddb/shared/IDBIndexInfo.cpp:
(WebCore::IDBIndexInfo::loggingString const): Ditto.
(WebCore::IDBIndexInfo::condensedLoggingString const): Ditto.
* Modules/indexeddb/shared/IDBIterateCursorData.cpp:
(WebCore::IDBIterateCursorData::loggingString const): Ditto.
* Modules/indexeddb/shared/IDBObjectStoreInfo.cpp:
(WebCore::IDBObjectStoreInfo::condensedLoggingString const): Ditto.
* Modules/indexeddb/shared/IDBResourceIdentifier.cpp:
(WebCore::IDBResourceIdentifier::loggingString const): Ditto.
* Modules/webdatabase/Database.cpp:
(WebCore::formatErrorMessage): Ditto.
* Modules/webdatabase/SQLError.h:
(WebCore::SQLError::create): Ditto.

* bindings/scripts/CodeGeneratorJS.pm:
(GenerateImplementation): Use makeString.

* bindings/scripts/test/JS/JSInterfaceName.cpp:
* bindings/scripts/test/JS/JSMapLike.cpp:
* bindings/scripts/test/JS/JSReadOnlyMapLike.cpp:
* bindings/scripts/test/JS/JSTestActiveDOMObject.cpp:
* bindings/scripts/test/JS/JSTestCEReactions.cpp:
* bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp:
* bindings/scripts/test/JS/JSTestCallTracer.cpp:
* bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp:
* bindings/scripts/test/JS/JSTestCustomConstructorWithNoInterfaceObject.cpp:
* bindings/scripts/test/JS/JSTestDOMJIT.cpp:
* bindings/scripts/test/JS/JSTestEnabledBySetting.cpp:
* bindings/scripts/test/JS/JSTestEventConstructor.cpp:
* bindings/scripts/test/JS/JSTestEventTarget.cpp:
* bindings/scripts/test/JS/JSTestException.cpp:
* bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp:
* bindings/scripts/test/JS/JSTestGlobalObject.cpp:
* bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp:
* bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp:
* bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp:
* bindings/scripts/test/JS/JSTestInterface.cpp:
* bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp:
* bindings/scripts/test/JS/JSTestIterable.cpp:
* bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp:
* bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp:
* bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedConstructor.cpp:
* bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp:
* bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp:
* bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp:
* bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp:
* bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp:
* bindings/scripts/test/JS/JSTestNode.cpp:
* bindings/scripts/test/JS/JSTestObj.cpp:
* bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp:
* bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp:
* bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp:
* bindings/scripts/test/JS/JSTestPluginInterface.cpp:
* bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp:
* bindings/scripts/test/JS/JSTestSerialization.cpp:
* bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp:
* bindings/scripts/test/JS/JSTestSerializationInherit.cpp:
* bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp:
* bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp:
* bindings/scripts/test/JS/JSTestStringifier.cpp:
* bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp:
* bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp:
* bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp:
* bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp:
* bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp:
* bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp:
* bindings/scripts/test/JS/JSTestTypedefs.cpp:
Updated expected results.

Source/WebKit:

* Shared/WebMemorySampler.cpp:
(WebKit::WebMemorySampler::writeHeaders): Use makeString.

* UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm:
(WebKit::LocalAuthenticator::makeCredential): Use string concatentation.

* UIProcess/WebInspectorUtilities.cpp:
(WebKit::inspectorPageGroupIdentifierForPage): Use makeString.
* UIProcess/WebProcessPool.cpp:
(WebKit::WebProcessPool::processDidFinishLaunching): Ditto.
(WebKit::WebProcessPool::startMemorySampler): Ditto.

Source/WebKitLegacy:

* Shared/WebMemorySampler.cpp:
(WebKit::WebMemorySampler::writeHeaders): Use makeString.

* UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm:
(WebKit::LocalAuthenticator::makeCredential): Use string concatentation.

* UIProcess/WebInspectorUtilities.cpp:
(WebKit::inspectorPageGroupIdentifierForPage): Use makeString.
* UIProcess/WebProcessPool.cpp:
(WebKit::WebProcessPool::processDidFinishLaunching): Ditto.
(WebKit::WebProcessPool::startMemorySampler): Ditto.

Source/WTF:

* wtf/WorkQueue.cpp:
(WTF::WorkQueue::concurrentApply): Use makeString.

* wtf/dtoa.cpp:
(WTF::dtoa): Use sprintf instead of String::format in the comments,
since these functions have nothing to do with WTF::String.

Tools:

* WebKitTestRunner/InjectedBundle/TestRunner.cpp:
(WTR::cacheTestRunnerCallback): Use makeString.
* WebKitTestRunner/TestController.cpp:
(WTR::TestController::didReceiveAuthenticationChallenge): Use makeString.
(WTR::TestController::downloadDidFail): Use an ASCIILiteral via the _s syntax.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@240557 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/ChangeLog b/Source/JavaScriptCore/ChangeLog
index ac6f664..848e889 100644
--- a/Source/JavaScriptCore/ChangeLog
+++ b/Source/JavaScriptCore/ChangeLog
@@ -1,3 +1,29 @@
+2018-12-15  Darin Adler  <darin@apple.com>
+
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        * inspector/InjectedScriptBase.cpp:
+        (Inspector::InjectedScriptBase::makeCall): Use makeString.
+        (Inspector::InjectedScriptBase::makeAsyncCall): Ditto.
+        * inspector/InspectorBackendDispatcher.cpp:
+        (Inspector::BackendDispatcher::getPropertyValue): Ditto.
+        * inspector/agents/InspectorConsoleAgent.cpp:
+        (Inspector::InspectorConsoleAgent::enable): Ditto.
+        * jsc.cpp:
+        (FunctionJSCStackFunctor::operator() const): Ditto.
+
+        * runtime/CodeCache.cpp:
+        (JSC::writeCodeBlock): Use makeString's numeric capabilities instead of
+        using String::number.
+
+        * runtime/IntlDateTimeFormat.cpp:
+        (JSC::IntlDateTimeFormat::initializeDateTimeFormat): Use string concatenation.
+        * runtime/IntlObject.cpp:
+        (JSC::canonicalizeLocaleList): Ditto.
+
 2019-01-27  Chris Fleizach  <cfleizach@apple.com>
 
         AX: Introduce a static accessibility tree
diff --git a/Source/JavaScriptCore/inspector/InjectedScriptBase.cpp b/Source/JavaScriptCore/inspector/InjectedScriptBase.cpp
index 91d0c7f..fd8bbcf 100644
--- a/Source/JavaScriptCore/inspector/InjectedScriptBase.cpp
+++ b/Source/JavaScriptCore/inspector/InjectedScriptBase.cpp
@@ -40,7 +40,7 @@
 #include "NativeStdFunctionCell.h"
 #include "ScriptFunctionCall.h"
 #include <wtf/JSONValues.h>
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace Inspector {
 
@@ -91,7 +91,7 @@
 
     RefPtr<JSON::Value> resultJSONValue = toInspectorValue(*m_injectedScriptObject.scriptState(), resultJSValue);
     if (!resultJSONValue)
-        return JSON::Value::create(String::format("Object has too long reference chain (must not be longer than %d)", JSON::Value::maxDepth));
+        return JSON::Value::create(makeString("Object has too long reference chain (must not be longer than ", JSON::Value::maxDepth, ')'));
 
     return resultJSONValue.releaseNonNull();
 }
@@ -122,7 +122,7 @@
             if (auto resultJSONValue = toInspectorValue(*exec, exec->argument(0)))
                 checkAsyncCallResult(resultJSONValue, callback);
             else
-                checkAsyncCallResult(JSON::Value::create(String::format("Object has too long reference chain (must not be longer than %d)", JSON::Value::maxDepth)), callback);
+                checkAsyncCallResult(JSON::Value::create(makeString("Object has too long reference chain (must not be longer than ", JSON::Value::maxDepth, ')')), callback);
             return JSC::JSValue::encode(JSC::jsUndefined());
         });
     }
diff --git a/Source/JavaScriptCore/inspector/InspectorBackendDispatcher.cpp b/Source/JavaScriptCore/inspector/InspectorBackendDispatcher.cpp
index 5cbc0da..fdefd42 100644
--- a/Source/JavaScriptCore/inspector/InspectorBackendDispatcher.cpp
+++ b/Source/JavaScriptCore/inspector/InspectorBackendDispatcher.cpp
@@ -289,19 +289,19 @@
 
     if (!object) {
         if (!out_optionalValueFound)
-            reportProtocolError(BackendDispatcher::InvalidParams, String::format("'params' object must contain required parameter '%s' with type '%s'.", name.utf8().data(), typeName));
+            reportProtocolError(BackendDispatcher::InvalidParams, makeString("'params' object must contain required parameter '", name, "' with type '", typeName, "'."));
         return result;
     }
 
     auto findResult = object->find(name);
     if (findResult == object->end()) {
         if (!out_optionalValueFound)
-            reportProtocolError(BackendDispatcher::InvalidParams, String::format("Parameter '%s' with type '%s' was not found.", name.utf8().data(), typeName));
+            reportProtocolError(BackendDispatcher::InvalidParams, makeString("Parameter '", name, "' with type '", typeName, "' was not found."));
         return result;
     }
 
     if (!asMethod(*findResult->value, result)) {
-        reportProtocolError(BackendDispatcher::InvalidParams, String::format("Parameter '%s' has wrong type. It must be '%s'.", name.utf8().data(), typeName));
+        reportProtocolError(BackendDispatcher::InvalidParams, makeString("Parameter '", name, "' has wrong type. It must be '", typeName, "'."));
         return result;
     }
 
diff --git a/Source/JavaScriptCore/inspector/agents/InspectorConsoleAgent.cpp b/Source/JavaScriptCore/inspector/agents/InspectorConsoleAgent.cpp
index 4cfed7c..3fc5e99 100644
--- a/Source/JavaScriptCore/inspector/agents/InspectorConsoleAgent.cpp
+++ b/Source/JavaScriptCore/inspector/agents/InspectorConsoleAgent.cpp
@@ -35,7 +35,7 @@
 #include "ScriptCallStack.h"
 #include "ScriptCallStackFactory.h"
 #include "ScriptObject.h"
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace Inspector {
 
@@ -79,7 +79,7 @@
     m_enabled = true;
 
     if (m_expiredConsoleMessageCount) {
-        ConsoleMessage expiredMessage(MessageSource::Other, MessageType::Log, MessageLevel::Warning, String::format("%d console messages are not shown.", m_expiredConsoleMessageCount));
+        ConsoleMessage expiredMessage(MessageSource::Other, MessageType::Log, MessageLevel::Warning, makeString(m_expiredConsoleMessageCount, " console messages are not shown."));
         expiredMessage.addToFrontend(*m_frontendDispatcher, m_injectedScriptManager, false);
     }
 
diff --git a/Source/JavaScriptCore/jsc.cpp b/Source/JavaScriptCore/jsc.cpp
index deba637..7884013 100644
--- a/Source/JavaScriptCore/jsc.cpp
+++ b/Source/JavaScriptCore/jsc.cpp
@@ -91,6 +91,7 @@
 #include <wtf/URL.h>
 #include <wtf/WallTime.h>
 #include <wtf/text/StringBuilder.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 #if OS(WINDOWS)
 #include <direct.h>
@@ -1172,7 +1173,7 @@
 
     StackVisitor::Status operator()(StackVisitor& visitor) const
     {
-        m_trace.append(String::format("    %zu   %s\n", visitor->index(), visitor->toString().utf8().data()));
+        m_trace.append(makeString("    ", visitor->index(), "   ", visitor->toString(), '\n'));
         return StackVisitor::Continue;
     }
 
diff --git a/Source/JavaScriptCore/runtime/CodeCache.cpp b/Source/JavaScriptCore/runtime/CodeCache.cpp
index 26e0931..b41e526 100644
--- a/Source/JavaScriptCore/runtime/CodeCache.cpp
+++ b/Source/JavaScriptCore/runtime/CodeCache.cpp
@@ -27,6 +27,7 @@
 #include "CodeCache.h"
 
 #include "IndirectEvalExecutable.h"
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace JSC {
 
@@ -196,7 +197,7 @@
 
     std::pair<MallocPtr<uint8_t>, size_t> result = encodeCodeBlock(vm, key, codeBlock);
 
-    String filename = makeString(cachePath, '/', String::number(key.hash()), ".cache");
+    String filename = makeString(cachePath, '/', key.hash(), ".cache");
     int fd = open(filename.utf8().data(), O_CREAT | O_WRONLY, 0666);
     if (fd == -1)
         return;
diff --git a/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp b/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp
index ae3d680..1e8d9e3 100644
--- a/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp
+++ b/Source/JavaScriptCore/runtime/IntlDateTimeFormat.cpp
@@ -504,7 +504,7 @@
         RETURN_IF_EXCEPTION(scope, void());
         tz = canonicalizeTimeZoneName(originalTz);
         if (tz.isNull()) {
-            throwRangeError(&exec, scope, String::format("invalid time zone: %s", originalTz.utf8().data()));
+            throwRangeError(&exec, scope, "invalid time zone: " + originalTz);
             return;
         }
     } else
diff --git a/Source/JavaScriptCore/runtime/IntlObject.cpp b/Source/JavaScriptCore/runtime/IntlObject.cpp
index 35c0b88..e17493a 100644
--- a/Source/JavaScriptCore/runtime/IntlObject.cpp
+++ b/Source/JavaScriptCore/runtime/IntlObject.cpp
@@ -592,7 +592,7 @@
 
             String canonicalizedTag = canonicalizeLanguageTag(tag->value(&state));
             if (canonicalizedTag.isNull()) {
-                throwException(&state, scope, createRangeError(&state, String::format("invalid language tag: %s", tag->value(&state).utf8().data())));
+                throwException(&state, scope, createRangeError(&state, "invalid language tag: " + tag->value(&state)));
                 return Vector<String>();
             }
 
diff --git a/Source/WTF/ChangeLog b/Source/WTF/ChangeLog
index 6e84d9c..8c19465 100644
--- a/Source/WTF/ChangeLog
+++ b/Source/WTF/ChangeLog
@@ -1,3 +1,17 @@
+2018-12-15  Darin Adler  <darin@apple.com>
+
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        * wtf/WorkQueue.cpp:
+        (WTF::WorkQueue::concurrentApply): Use makeString.
+
+        * wtf/dtoa.cpp:
+        (WTF::dtoa): Use sprintf instead of String::format in the comments,
+        since these functions have nothing to do with WTF::String.
+
 2019-01-25  Chris Dumez  <cdumez@apple.com>
 
         [iOS] Add support for the download attribute
diff --git a/Source/WTF/wtf/WorkQueue.cpp b/Source/WTF/wtf/WorkQueue.cpp
index 441b12d..288c186 100644
--- a/Source/WTF/wtf/WorkQueue.cpp
+++ b/Source/WTF/wtf/WorkQueue.cpp
@@ -36,7 +36,7 @@
 #include <wtf/NumberOfCores.h>
 #include <wtf/Ref.h>
 #include <wtf/Threading.h>
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WTF {
 
diff --git a/Source/WTF/wtf/dtoa.cpp b/Source/WTF/wtf/dtoa.cpp
index 8465583..683314f 100644
--- a/Source/WTF/wtf/dtoa.cpp
+++ b/Source/WTF/wtf/dtoa.cpp
@@ -1272,7 +1272,7 @@
 
 const char* numberToFixedPrecisionString(double d, unsigned significantFigures, NumberToStringBuffer buffer, bool truncateTrailingZeros)
 {
-    // Mimic String::format("%.[precision]g", ...), but use dtoas rounding facilities.
+    // Mimic sprintf("%.[precision]g", ...), but use dtoas rounding facilities.
     // "g": Signed value printed in f or e format, whichever is more compact for the given value and precision.
     // The e format is used only when the exponent of the value is less than –4 or greater than or equal to the
     // precision argument. Trailing zeros are truncated, and the decimal point appears only if one or more digits follow it.
@@ -1287,7 +1287,7 @@
 
 const char* numberToFixedWidthString(double d, unsigned decimalPlaces, NumberToStringBuffer buffer)
 {
-    // Mimic String::format("%.[precision]f", ...), but use dtoas rounding facilities.
+    // Mimic sprintf("%.[precision]f", ...), but use dtoas rounding facilities.
     // "f": Signed value having the form [ – ]dddd.dddd, where dddd is one or more decimal digits.
     // The number of digits before the decimal point depends on the magnitude of the number, and
     // the number of digits after the decimal point depends on the requested precision.
diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index d01af33..a84d958 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,183 @@
+2018-12-15  Darin Adler  <darin@apple.com>
+
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        A while back, String::format was more efficient than string concatenation,
+        but that is no longer true, and we should prefer String::number, makeString,
+        or concatenation with the "+" operator to String::format for new code.
+
+        This is not as good for programmers who are fond of printf formatting
+        style, and in some cases it's a little harder to read the strings
+        interspersed with variables rather than a format string, but it's better
+        in a few ways:
+
+        - more efficient (I didn't measure the difference, but it's definitely
+          slower to use String::Format which calls vsnprintf twice than to use
+          the WTF code)
+        - works in a type-safe way without a need to use a format specifier such
+          as "%" PRIu64 or "%tu" making it much easier to avoid problems due to
+          subtle differences between platforms
+        - allows us to use StringView in some cases to sidestep the need to
+          allocate temporary WTF::String objects
+        - does not require converting each WTF::String to a C string, allowing
+          us to remove many cases of ".utf8().data()" and similar expressions,
+          eliminating the allocation of temporary WTF::CString objects
+
+        This patch covers a batch of easiest-to-convert call sites.
+        Later patches will allow us to deprecate or remove String::format.
+
+        * Modules/indexeddb/server/SQLiteIDBBackingStore.cpp:
+        (WebCore::IDBServer::SQLiteIDBBackingStore::addRecord): Use makeString.
+        * Modules/indexeddb/shared/IDBCursorInfo.cpp:
+        (WebCore::IDBCursorInfo::loggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBGetAllRecordsData.cpp:
+        (WebCore::IDBGetAllRecordsData::loggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBGetRecordData.cpp:
+        (WebCore::IDBGetRecordData::loggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBIndexInfo.cpp:
+        (WebCore::IDBIndexInfo::loggingString const): Ditto.
+        (WebCore::IDBIndexInfo::condensedLoggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBIterateCursorData.cpp:
+        (WebCore::IDBIterateCursorData::loggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBObjectStoreInfo.cpp:
+        (WebCore::IDBObjectStoreInfo::condensedLoggingString const): Ditto.
+        * Modules/indexeddb/shared/IDBResourceIdentifier.cpp:
+        (WebCore::IDBResourceIdentifier::loggingString const): Ditto.
+        * Modules/webdatabase/Database.cpp:
+        (WebCore::formatErrorMessage): Ditto.
+        * Modules/webdatabase/SQLError.h:
+        (WebCore::SQLError::create): Ditto.
+
+        * bindings/scripts/CodeGeneratorJS.pm:
+        (GenerateImplementation): Use makeString.
+
+        * bindings/scripts/test/JS/JSInterfaceName.cpp:
+        * bindings/scripts/test/JS/JSMapLike.cpp:
+        * bindings/scripts/test/JS/JSReadOnlyMapLike.cpp:
+        * bindings/scripts/test/JS/JSTestActiveDOMObject.cpp:
+        * bindings/scripts/test/JS/JSTestCEReactions.cpp:
+        * bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp:
+        * bindings/scripts/test/JS/JSTestCallTracer.cpp:
+        * bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp:
+        * bindings/scripts/test/JS/JSTestCustomConstructorWithNoInterfaceObject.cpp:
+        * bindings/scripts/test/JS/JSTestDOMJIT.cpp:
+        * bindings/scripts/test/JS/JSTestEnabledBySetting.cpp:
+        * bindings/scripts/test/JS/JSTestEventConstructor.cpp:
+        * bindings/scripts/test/JS/JSTestEventTarget.cpp:
+        * bindings/scripts/test/JS/JSTestException.cpp:
+        * bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp:
+        * bindings/scripts/test/JS/JSTestGlobalObject.cpp:
+        * bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp:
+        * bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestInterface.cpp:
+        * bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp:
+        * bindings/scripts/test/JS/JSTestIterable.cpp:
+        * bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp:
+        * bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp:
+        * bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedConstructor.cpp:
+        * bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp:
+        * bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp:
+        * bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp:
+        * bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp:
+        * bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp:
+        * bindings/scripts/test/JS/JSTestNode.cpp:
+        * bindings/scripts/test/JS/JSTestObj.cpp:
+        * bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp:
+        * bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp:
+        * bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp:
+        * bindings/scripts/test/JS/JSTestPluginInterface.cpp:
+        * bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp:
+        * bindings/scripts/test/JS/JSTestSerialization.cpp:
+        * bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp:
+        * bindings/scripts/test/JS/JSTestSerializationInherit.cpp:
+        * bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp:
+        * bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp:
+        * bindings/scripts/test/JS/JSTestStringifier.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp:
+        * bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp:
+        * bindings/scripts/test/JS/JSTestTypedefs.cpp:
+        Updated expected results.
+:
+        * css/parser/CSSPropertyParserHelpers.cpp:
+        (WebCore::CSSPropertyParserHelpers::parseHexColor): Use String::number
+        and makeString.
+
+        * html/HTMLSelectElement.cpp:
+        (WebCore::HTMLSelectElement::setLength): Use makeString.
+        * html/ImageDocument.cpp:
+        (WebCore::ImageDocument::imageUpdated): Ditto.
+        * html/parser/XSSAuditor.cpp:
+        (WebCore::XSSAuditor::init): Ditto.
+        * inspector/InspectorFrontendClientLocal.cpp:
+        (WebCore::InspectorFrontendClientLocal::setDockingUnavailable): Ditto.
+        (WebCore::InspectorFrontendClientLocal::setAttachedWindow): Ditto.
+        (WebCore::InspectorFrontendClientLocal::setDebuggingEnabled): Ditto.
+        (WebCore::InspectorFrontendClientLocal::setTimelineProfilingEnabled): Ditto.
+        (WebCore::InspectorFrontendClientLocal::showMainResourceForFrame): Ditto.
+        * inspector/agents/InspectorCSSAgent.cpp: Ditto.
+        * inspector/agents/InspectorIndexedDBAgent.cpp: Ditto.
+        * page/MemoryRelease.cpp:
+        (WebCore::logMemoryStatisticsAtTimeOfDeath): Ditto.
+
+        * page/cocoa/ResourceUsageOverlayCocoa.mm:
+        (WebCore::formatByteNumber): Use String::number.
+        (WebCore::ResourceUsageOverlay::platformDraw): Use string concatenation.
+
+        * page/cocoa/ResourceUsageThreadCocoa.mm:
+        (WebCore::logFootprintComparison): Use makeString.
+        * platform/animation/TimingFunction.cpp:
+        (WebCore::TimingFunction::cssText const): Ditto.
+
+        * platform/graphics/avfoundation/AVTrackPrivateAVFObjCImpl.mm:
+        (WebCore::AVTrackPrivateAVFObjCImpl::id const): Use AtomicString::number.
+        * platform/graphics/avfoundation/objc/MediaSampleAVFObjC.h:
+        (WebCore::MediaSampleAVFObjC::MediaSampleAVFObjC): Ditto.
+
+        * platform/graphics/ca/GraphicsLayerCA.cpp:
+        (WebCore::GraphicsLayerCA::setContentsToSolidColor): Use makeString.
+        (WebCore::GraphicsLayerCA::updateContentsImage): Ditto.
+        (WebCore::GraphicsLayerCA::updateContentsRects): Ditto.
+        (WebCore::GraphicsLayerCA::createTransformAnimationsFromKeyframes): Ditto.
+        * platform/mock/MockRealtimeVideoSource.cpp:
+        (WebCore::MockRealtimeVideoSource::drawText): Ditto.
+
+        * platform/mock/mediasource/MockSourceBufferPrivate.cpp: Use String::number.
+
+        * platform/network/ParsedContentRange.cpp:
+        (WebCore::ParsedContentRange::headerValue const): Use makeString.
+
+        * platform/network/cf/NetworkStorageSessionCFNet.cpp: Removed some unnecessary
+        compiler conditionals and reorganized the start/stop of namespaces.
+        (WebCore::NetworkStorageSession::switchToNewTestingSession): Use makeString.
+
+        * platform/sql/SQLiteDatabase.cpp:
+        (WebCore::unauthorizedSQLFunction): Use makeString.
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::logLayerInfo): Ditto.
+        * workers/service/server/RegistrationDatabase.cpp:
+        (WebCore::RegistrationDatabase::ensureValidRecordsTable): Ditto.
+        (WebCore::RegistrationDatabase::importRecords): Ditto.
+
 2019-01-27  Wenson Hsieh  <wenson_hsieh@apple.com>
 
         Remove a couple of PLATFORM defines intended for watchOS
diff --git a/Source/WebCore/Modules/indexeddb/server/SQLiteIDBBackingStore.cpp b/Source/WebCore/Modules/indexeddb/server/SQLiteIDBBackingStore.cpp
index 285d502..7415ec8 100644
--- a/Source/WebCore/Modules/indexeddb/server/SQLiteIDBBackingStore.cpp
+++ b/Source/WebCore/Modules/indexeddb/server/SQLiteIDBBackingStore.cpp
@@ -55,6 +55,7 @@
 #include <JavaScriptCore/StructureInlines.h>
 #include <wtf/FileSystem.h>
 #include <wtf/NeverDestroyed.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 using namespace JSC;
@@ -1844,7 +1845,7 @@
         }
 
         // We don't already have a file for this blobURL, so commit our file as a unique filename
-        String storedFilename = String::format("%" PRId64 ".blob", potentialFileNameInteger);
+        String storedFilename = makeString(potentialFileNameInteger, ".blob");
         {
             auto* sql = cachedStatement(SQL::AddBlobFilename, "INSERT INTO BlobFiles VALUES (?, ?);"_s);
             if (!sql
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBCursorInfo.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBCursorInfo.cpp
index 0d3e338..0e6d9cd 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBCursorInfo.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBCursorInfo.cpp
@@ -31,6 +31,7 @@
 #include "IDBDatabase.h"
 #include "IDBTransaction.h"
 #include "IndexedDB.h"
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -100,13 +101,15 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBCursorInfo::loggingString() const
 {
     if (m_source == IndexedDB::CursorSource::Index)
-        return String::format("<Crsr: %s Idx %" PRIu64 ", OS %" PRIu64 ", tx %s>", m_cursorIdentifier.loggingString().utf8().data(), m_sourceIdentifier, m_objectStoreIdentifier, m_transactionIdentifier.loggingString().utf8().data());
+        return makeString("<Crsr: ", m_cursorIdentifier.loggingString(), " Idx ", m_sourceIdentifier, ", OS ", m_objectStoreIdentifier, ", tx ", m_transactionIdentifier.loggingString(), '>');
 
-    return String::format("<Crsr: %s OS %" PRIu64 ", tx %s>", m_cursorIdentifier.loggingString().utf8().data(), m_objectStoreIdentifier, m_transactionIdentifier.loggingString().utf8().data());
+    return makeString("<Crsr: ", m_cursorIdentifier.loggingString(), " OS ", m_objectStoreIdentifier, ", tx ", m_transactionIdentifier.loggingString(), '>');
 }
+
 #endif
 
 } // namespace WebCore
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBGetAllRecordsData.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBGetAllRecordsData.cpp
index 92b6b92..c985d74 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBGetAllRecordsData.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBGetAllRecordsData.cpp
@@ -38,12 +38,14 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBGetAllRecordsData::loggingString() const
 {
     if (indexIdentifier)
-        return String::format("<GetAllRecords: Idx %" PRIu64 ", OS %" PRIu64 ", %s, range %s>", indexIdentifier, objectStoreIdentifier, getAllType == IndexedDB::GetAllType::Keys ? "Keys" : "Values", keyRangeData.loggingString().utf8().data());
-    return String::format("<GetAllRecords: OS %" PRIu64 ", %s, range %s>", objectStoreIdentifier, getAllType == IndexedDB::GetAllType::Keys ? "Keys" : "Values", keyRangeData.loggingString().utf8().data());
+        return makeString("<GetAllRecords: Idx ", indexIdentifier, ", OS ", objectStoreIdentifier, ", ", getAllType == IndexedDB::GetAllType::Keys ? "Keys" : "Values", ", range ", keyRangeData.loggingString(), '>');
+    return makeString("<GetAllRecords: OS ", objectStoreIdentifier, ", ", getAllType == IndexedDB::GetAllType::Keys ? "Keys" : "Values", ", range ", keyRangeData.loggingString(), '>');
 }
+
 #endif
 
 } // namespace WebCore
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBGetRecordData.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBGetRecordData.cpp
index d789626..46346dc 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBGetRecordData.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBGetRecordData.cpp
@@ -38,10 +38,12 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBGetRecordData::loggingString() const
 {
-    return String::format("<GetRecord: %s %s>", type == IDBGetRecordDataType::KeyOnly ? "KeyOnly" : "Key+Value", keyRangeData.loggingString().utf8().data());
+    return makeString("<GetRecord: ", type == IDBGetRecordDataType::KeyOnly ? "KeyOnly" : "Key+Value", ' ', keyRangeData.loggingString(), '>');
 }
+
 #endif
 
 } // namespace WebCore
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBIndexInfo.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBIndexInfo.cpp
index 27290f4..12c5e6f 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBIndexInfo.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBIndexInfo.cpp
@@ -28,6 +28,8 @@
 
 #if ENABLE(INDEXED_DATABASE)
 
+#include <wtf/text/StringConcatenateNumbers.h>
+
 namespace WebCore {
 
 IDBIndexInfo::IDBIndexInfo()
@@ -50,19 +52,20 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBIndexInfo::loggingString(int indent) const
 {
     String indentString;
     for (int i = 0; i < indent; ++i)
         indentString.append(" ");
-
-    return makeString(indentString, "Index: ", m_name, String::format(" (%" PRIu64 ") keyPath: %s\n", m_identifier, WebCore::loggingString(m_keyPath).utf8().data()));
+    return makeString(indentString, "Index: ", m_name, " (", m_identifier, ") keyPath: ", WebCore::loggingString(m_keyPath), '\n');
 }
 
 String IDBIndexInfo::condensedLoggingString() const
 {
-    return String::format("<Idx: %s (%" PRIu64 "), OS (%" PRIu64 ")>", m_name.utf8().data(), m_identifier, m_objectStoreIdentifier);
+    return makeString("<Idx: ", m_name, " (", m_identifier, "), OS (", m_objectStoreIdentifier, ")>");
 }
+
 #endif
 
 } // namespace WebCore
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBIterateCursorData.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBIterateCursorData.cpp
index faaeda9..593e148 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBIterateCursorData.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBIterateCursorData.cpp
@@ -36,10 +36,12 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBIterateCursorData::loggingString() const
 {
-    return String::format("<Itr8Crsr: key %s, primaryKey %s, count %u>", keyData.loggingString().utf8().data(), primaryKeyData.loggingString().utf8().data(), count);
+    return makeString("<Itr8Crsr: key ", keyData.loggingString(), ", primaryKey ", primaryKeyData.loggingString(), ", count ", count, '>');
 }
+
 #endif
 
 } // namespace WebCore
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBObjectStoreInfo.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBObjectStoreInfo.cpp
index 04ca90b..2938e93 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBObjectStoreInfo.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBObjectStoreInfo.cpp
@@ -153,7 +153,7 @@
 
 String IDBObjectStoreInfo::condensedLoggingString() const
 {
-    return String::format("<OS: %s (%" PRIu64 ")>", m_name.utf8().data(), m_identifier);
+    return makeString("<OS: ", m_name, " (", m_identifier, ")>");
 }
 
 #endif
diff --git a/Source/WebCore/Modules/indexeddb/shared/IDBResourceIdentifier.cpp b/Source/WebCore/Modules/indexeddb/shared/IDBResourceIdentifier.cpp
index f673b2d..616d54f 100644
--- a/Source/WebCore/Modules/indexeddb/shared/IDBResourceIdentifier.cpp
+++ b/Source/WebCore/Modules/indexeddb/shared/IDBResourceIdentifier.cpp
@@ -99,11 +99,14 @@
 }
 
 #if !LOG_DISABLED
+
 String IDBResourceIdentifier::loggingString() const
 {
-    return String::format("<%" PRIu64", %" PRIu64">", m_idbConnectionIdentifier, m_resourceNumber);
+    return makeString('<', m_idbConnectionIdentifier, ", ", m_resourceNumber, '>');
 }
+
 #endif
+
 } // namespace WebCore
 
 #endif // ENABLE(INDEXED_DATABASE)
diff --git a/Source/WebCore/Modules/webdatabase/Database.cpp b/Source/WebCore/Modules/webdatabase/Database.cpp
index c875f3b..7a53fec 100644
--- a/Source/WebCore/Modules/webdatabase/Database.cpp
+++ b/Source/WebCore/Modules/webdatabase/Database.cpp
@@ -107,7 +107,7 @@
 
 static String formatErrorMessage(const char* message, int sqliteErrorCode, const char* sqliteErrorMessage)
 {
-    return String::format("%s (%d %s)", message, sqliteErrorCode, sqliteErrorMessage);
+    return makeString(message, " (", sqliteErrorCode, ' ', sqliteErrorMessage, ')');
 }
 
 static bool setTextValueInDatabase(SQLiteDatabase& db, const String& query, const String& value)
diff --git a/Source/WebCore/Modules/webdatabase/SQLError.h b/Source/WebCore/Modules/webdatabase/SQLError.h
index 4e276ca..6b072bb 100644
--- a/Source/WebCore/Modules/webdatabase/SQLError.h
+++ b/Source/WebCore/Modules/webdatabase/SQLError.h
@@ -29,7 +29,7 @@
 #pragma once
 
 #include <wtf/ThreadSafeRefCounted.h>
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -38,11 +38,11 @@
     static Ref<SQLError> create(unsigned code, const String& message) { return adoptRef(*new SQLError(code, message)); }
     static Ref<SQLError> create(unsigned code, const char* message, int sqliteCode)
     {
-        return create(code, String::format("%s (%d)", message, sqliteCode));
+        return create(code, makeString(message, " (", sqliteCode, ')'));
     }
     static Ref<SQLError> create(unsigned code, const char* message, int sqliteCode, const char* sqliteMessage)
     {
-        return create(code, String::format("%s (%d %s)", message, sqliteCode, sqliteMessage));
+        return create(code, makeString(message, " (", sqliteCode, ' ', sqliteMessage, ')'));
     }
 
     unsigned code() const { return m_code; }
diff --git a/Source/WebCore/bindings/scripts/CodeGeneratorJS.pm b/Source/WebCore/bindings/scripts/CodeGeneratorJS.pm
index f92ed2d..6af893d 100644
--- a/Source/WebCore/bindings/scripts/CodeGeneratorJS.pm
+++ b/Source/WebCore/bindings/scripts/CodeGeneratorJS.pm
@@ -4572,7 +4572,7 @@
         push(@implContent, "    auto* thisObject = jsCast<${className}*>(cell);\n");
         push(@implContent, "    builder.setWrappedObjectForCell(cell, &thisObject->wrapped());\n");
         push(@implContent, "    if (thisObject->scriptExecutionContext())\n");
-        push(@implContent, "        builder.setLabelForCell(cell, String::format(\"url %s\", thisObject->scriptExecutionContext()->url().string().utf8().data()));\n");
+        push(@implContent, "        builder.setLabelForCell(cell, \"url \" + thisObject->scriptExecutionContext()->url().string());\n");
         push(@implContent, "    Base::heapSnapshot(cell, builder);\n");
         push(@implContent, "}\n\n");
     }
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSInterfaceName.cpp b/Source/WebCore/bindings/scripts/test/JS/JSInterfaceName.cpp
index 6d9bd17..141eb8e 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSInterfaceName.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSInterfaceName.cpp
@@ -176,7 +176,7 @@
     auto* thisObject = jsCast<JSInterfaceName*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSMapLike.cpp b/Source/WebCore/bindings/scripts/test/JS/JSMapLike.cpp
index 079c666..3567a72 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSMapLike.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSMapLike.cpp
@@ -345,7 +345,7 @@
     auto* thisObject = jsCast<JSMapLike*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSReadOnlyMapLike.cpp b/Source/WebCore/bindings/scripts/test/JS/JSReadOnlyMapLike.cpp
index 97d4f3a..ab281f0 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSReadOnlyMapLike.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSReadOnlyMapLike.cpp
@@ -294,7 +294,7 @@
     auto* thisObject = jsCast<JSReadOnlyMapLike*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestActiveDOMObject.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestActiveDOMObject.cpp
index 6cc23ad..2b61417 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestActiveDOMObject.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestActiveDOMObject.cpp
@@ -255,7 +255,7 @@
     auto* thisObject = jsCast<JSTestActiveDOMObject*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactions.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactions.cpp
index 4a02793..a1bdab1 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactions.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactions.cpp
@@ -435,7 +435,7 @@
     auto* thisObject = jsCast<JSTestCEReactions*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp
index 342a0df..580e243 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestCEReactionsStringifier.cpp
@@ -264,7 +264,7 @@
     auto* thisObject = jsCast<JSTestCEReactionsStringifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestCallTracer.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestCallTracer.cpp
index 2e8de51..6b81bffe 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestCallTracer.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestCallTracer.cpp
@@ -528,7 +528,7 @@
     auto* thisObject = jsCast<JSTestCallTracer*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp
index 008b5e8..5c8c785 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestClassWithJSBuiltinConstructor.cpp
@@ -168,7 +168,7 @@
     auto* thisObject = jsCast<JSTestClassWithJSBuiltinConstructor*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestDOMJIT.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestDOMJIT.cpp
index 95d7670..83b0f7d 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestDOMJIT.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestDOMJIT.cpp
@@ -1266,7 +1266,7 @@
     auto* thisObject = jsCast<JSTestDOMJIT*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestEnabledBySetting.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestEnabledBySetting.cpp
index 660b977..4df8130 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestEnabledBySetting.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestEnabledBySetting.cpp
@@ -307,7 +307,7 @@
     auto* thisObject = jsCast<JSTestEnabledBySetting*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestEventConstructor.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestEventConstructor.cpp
index 45dc192..33e2f9d 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestEventConstructor.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestEventConstructor.cpp
@@ -311,7 +311,7 @@
     auto* thisObject = jsCast<JSTestEventConstructor*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestEventTarget.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestEventTarget.cpp
index 0ec0640..5fc7cb6 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestEventTarget.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestEventTarget.cpp
@@ -254,7 +254,7 @@
     auto* thisObject = jsCast<JSTestEventTarget*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestException.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestException.cpp
index d32c04c..36d6241 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestException.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestException.cpp
@@ -185,7 +185,7 @@
     auto* thisObject = jsCast<JSTestException*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp
index b0d9d49..9f16b82 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestGenerateIsReachable.cpp
@@ -194,7 +194,7 @@
     auto* thisObject = jsCast<JSTestGenerateIsReachable*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestGlobalObject.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestGlobalObject.cpp
index b20b83c..cec371f 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestGlobalObject.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestGlobalObject.cpp
@@ -614,7 +614,7 @@
     auto* thisObject = jsCast<JSTestGlobalObject*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp
index 5789253..093adcb 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterNoIdentifier.cpp
@@ -253,7 +253,7 @@
     auto* thisObject = jsCast<JSTestIndexedSetterNoIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp
index 355adcd..615802d 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterThrowingException.cpp
@@ -253,7 +253,7 @@
     auto* thisObject = jsCast<JSTestIndexedSetterThrowingException*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp
index 769673a..a871231 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestIndexedSetterWithIdentifier.cpp
@@ -285,7 +285,7 @@
     auto* thisObject = jsCast<JSTestIndexedSetterWithIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestInterface.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestInterface.cpp
index 6ea3f97..d6c41fb 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestInterface.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestInterface.cpp
@@ -1022,7 +1022,7 @@
     auto* thisObject = jsCast<JSTestInterface*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp
index cff32ff..c94182c 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestInterfaceLeadingUnderscore.cpp
@@ -185,7 +185,7 @@
     auto* thisObject = jsCast<JSTestInterfaceLeadingUnderscore*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestIterable.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestIterable.cpp
index ac1e8e7..1a92374 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestIterable.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestIterable.cpp
@@ -238,7 +238,7 @@
     auto* thisObject = jsCast<JSTestIterable*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp
index 00faf9f..fa78d03 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestMediaQueryListListener.cpp
@@ -194,7 +194,7 @@
     auto* thisObject = jsCast<JSTestMediaQueryListListener*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp
index 9531207..35b77a7 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterNoIdentifier.cpp
@@ -319,7 +319,7 @@
     auto* thisObject = jsCast<JSTestNamedAndIndexedSetterNoIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp
index 0595462..f1b1da1 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterThrowingException.cpp
@@ -319,7 +319,7 @@
     auto* thisObject = jsCast<JSTestNamedAndIndexedSetterThrowingException*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp
index 55b5af3..fb6089c 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedAndIndexedSetterWithIdentifier.cpp
@@ -373,7 +373,7 @@
     auto* thisObject = jsCast<JSTestNamedAndIndexedSetterWithIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedConstructor.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedConstructor.cpp
index f1a84a8..022d3cd 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedConstructor.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedConstructor.cpp
@@ -205,7 +205,7 @@
     auto* thisObject = jsCast<JSTestNamedConstructor*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp
index 97d826a..e7d91f8 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterNoIdentifier.cpp
@@ -233,7 +233,7 @@
     auto* thisObject = jsCast<JSTestNamedDeleterNoIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp
index d1ef306..a7d76ba 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterThrowingException.cpp
@@ -247,7 +247,7 @@
     auto* thisObject = jsCast<JSTestNamedDeleterThrowingException*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp
index e4fa391..9edab59 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIdentifier.cpp
@@ -264,7 +264,7 @@
     auto* thisObject = jsCast<JSTestNamedDeleterWithIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp
index cf4640b..2fb624a 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedDeleterWithIndexedGetter.cpp
@@ -250,7 +250,7 @@
     auto* thisObject = jsCast<JSTestNamedDeleterWithIndexedGetter*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp
index 41a6283..f595969 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterCallWith.cpp
@@ -212,7 +212,7 @@
     auto* thisObject = jsCast<JSTestNamedGetterCallWith*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp
index 249fc8d..fae104a 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterNoIdentifier.cpp
@@ -212,7 +212,7 @@
     auto* thisObject = jsCast<JSTestNamedGetterNoIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp
index ea02a42..918b2d6 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedGetterWithIdentifier.cpp
@@ -240,7 +240,7 @@
     auto* thisObject = jsCast<JSTestNamedGetterWithIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp
index f431ade3..021ce1e 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterNoIdentifier.cpp
@@ -274,7 +274,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterNoIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp
index 64437fc..052a1a2 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterThrowingException.cpp
@@ -274,7 +274,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterThrowingException*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp
index e82d799..0b8f5de 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIdentifier.cpp
@@ -305,7 +305,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithIdentifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp
index 65e3ed0..090da16 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetter.cpp
@@ -347,7 +347,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithIndexedGetter*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp
index a69d0d7..5d0ba23 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithIndexedGetterAndSetter.cpp
@@ -397,7 +397,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithIndexedGetterAndSetter*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp
index 1d84e78..f27629c 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithOverrideBuiltins.cpp
@@ -261,7 +261,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithOverrideBuiltins*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp
index d0e854e..d4d9738 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgableProperties.cpp
@@ -343,7 +343,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithUnforgableProperties*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp
index cbdbaa2..ce59e74 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins.cpp
@@ -330,7 +330,7 @@
     auto* thisObject = jsCast<JSTestNamedSetterWithUnforgablePropertiesAndOverrideBuiltins*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestNode.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestNode.cpp
index 35a2d623..264bf96 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestNode.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestNode.cpp
@@ -429,7 +429,7 @@
     auto* thisObject = jsCast<JSTestNode*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestObj.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestObj.cpp
index 21c10c7..eae2f29 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestObj.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestObj.cpp
@@ -8546,7 +8546,7 @@
     auto* thisObject = jsCast<JSTestObj*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp
index 1adb702..7708eda 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructors.cpp
@@ -257,7 +257,7 @@
     auto* thisObject = jsCast<JSTestOverloadedConstructors*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp
index b055668..3831269 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestOverloadedConstructorsWithSequence.cpp
@@ -213,7 +213,7 @@
     auto* thisObject = jsCast<JSTestOverloadedConstructorsWithSequence*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp
index 6c6c044..9b5a027 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestOverrideBuiltins.cpp
@@ -243,7 +243,7 @@
     auto* thisObject = jsCast<JSTestOverrideBuiltins*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestPluginInterface.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestPluginInterface.cpp
index bec57d5..c340edd 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestPluginInterface.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestPluginInterface.cpp
@@ -216,7 +216,7 @@
     auto* thisObject = jsCast<JSTestPluginInterface*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp
index 7a25898..c8da5dd 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestPromiseRejectionEvent.cpp
@@ -293,7 +293,7 @@
     auto* thisObject = jsCast<JSTestPromiseRejectionEvent*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestSerialization.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestSerialization.cpp
index 78d1c41..eaf57f8 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestSerialization.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestSerialization.cpp
@@ -550,7 +550,7 @@
     auto* thisObject = jsCast<JSTestSerialization*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp
index 133eda0..6492005 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationIndirectInheritance.cpp
@@ -154,7 +154,7 @@
     auto* thisObject = jsCast<JSTestSerializationIndirectInheritance*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInherit.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInherit.cpp
index ad531b2..4442f51 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInherit.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInherit.cpp
@@ -229,7 +229,7 @@
     auto* thisObject = jsCast<JSTestSerializationInherit*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp
index a1ac2d0..ba61bc5 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializationInheritFinal.cpp
@@ -263,7 +263,7 @@
     auto* thisObject = jsCast<JSTestSerializationInheritFinal*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp
index df7dfb8..42b2836 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestSerializedScriptValueInterface.cpp
@@ -353,7 +353,7 @@
     auto* thisObject = jsCast<JSTestSerializedScriptValueInterface*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifier.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifier.cpp
index 5242bb8..31392cb 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifier.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifier.cpp
@@ -187,7 +187,7 @@
     auto* thisObject = jsCast<JSTestStringifier*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp
index 7cae243..58cd0ff 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierAnonymousOperation.cpp
@@ -187,7 +187,7 @@
     auto* thisObject = jsCast<JSTestStringifierAnonymousOperation*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp
index 50a46f6..c9b25f0 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierNamedOperation.cpp
@@ -202,7 +202,7 @@
     auto* thisObject = jsCast<JSTestStringifierNamedOperation*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp
index 0a33af3..35d863a 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationImplementedAs.cpp
@@ -202,7 +202,7 @@
     auto* thisObject = jsCast<JSTestStringifierOperationImplementedAs*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp
index 4904917..6ba4cd1 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierOperationNamedToString.cpp
@@ -187,7 +187,7 @@
     auto* thisObject = jsCast<JSTestStringifierOperationNamedToString*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp
index c9c5269..41523a5 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadOnlyAttribute.cpp
@@ -209,7 +209,7 @@
     auto* thisObject = jsCast<JSTestStringifierReadOnlyAttribute*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp
index 75ec38a..7cc60e8 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestStringifierReadWriteAttribute.cpp
@@ -227,7 +227,7 @@
     auto* thisObject = jsCast<JSTestStringifierReadWriteAttribute*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/bindings/scripts/test/JS/JSTestTypedefs.cpp b/Source/WebCore/bindings/scripts/test/JS/JSTestTypedefs.cpp
index 0eb867e..906b66d 100644
--- a/Source/WebCore/bindings/scripts/test/JS/JSTestTypedefs.cpp
+++ b/Source/WebCore/bindings/scripts/test/JS/JSTestTypedefs.cpp
@@ -749,7 +749,7 @@
     auto* thisObject = jsCast<JSTestTypedefs*>(cell);
     builder.setWrappedObjectForCell(cell, &thisObject->wrapped());
     if (thisObject->scriptExecutionContext())
-        builder.setLabelForCell(cell, String::format("url %s", thisObject->scriptExecutionContext()->url().string().utf8().data()));
+        builder.setLabelForCell(cell, "url " + thisObject->scriptExecutionContext()->url().string());
     Base::heapSnapshot(cell, builder);
 }
 
diff --git a/Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp b/Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp
index e6dbed7..a52b195 100644
--- a/Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp
+++ b/Source/WebCore/css/parser/CSSPropertyParserHelpers.cpp
@@ -43,6 +43,7 @@
 #include "CSSValuePool.h"
 #include "Pair.h"
 #include "StyleColor.h"
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -721,9 +722,9 @@
                 || token.numericValue() < 0. || token.numericValue() >= 1000000.)
                 return Color();
             if (token.type() == NumberToken) // e.g. 112233
-                color = String::format("%d", static_cast<int>(token.numericValue()));
+                color = String::number(static_cast<int>(token.numericValue()));
             else // e.g. 0001FF
-                color = String::number(static_cast<int>(token.numericValue())) + token.value().toString();
+                color = makeString(static_cast<int>(token.numericValue()), token.value().toString());
             while (color.length() < 6)
                 color = "0" + color;
         } else if (token.type() == IdentToken) { // e.g. FF0000
diff --git a/Source/WebCore/html/HTMLSelectElement.cpp b/Source/WebCore/html/HTMLSelectElement.cpp
index 5de320e..d499b91 100644
--- a/Source/WebCore/html/HTMLSelectElement.cpp
+++ b/Source/WebCore/html/HTMLSelectElement.cpp
@@ -55,6 +55,7 @@
 #include "Settings.h"
 #include "SpatialNavigation.h"
 #include <wtf/IsoMallocInlines.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -458,7 +459,7 @@
 ExceptionOr<void> HTMLSelectElement::setLength(unsigned newLength)
 {
     if (newLength > length() && newLength > maxSelectItems) {
-        document().addConsoleMessage(MessageSource::Other, MessageLevel::Warning, String::format("Blocked attempt to expand the option list to %u items. The maximum number of items allowed is %u.", newLength, maxSelectItems));
+        document().addConsoleMessage(MessageSource::Other, MessageLevel::Warning, makeString("Blocked attempt to expand the option list to ", newLength, " items. The maximum number of items allowed is ", maxSelectItems, '.'));
         return { };
     }
 
diff --git a/Source/WebCore/html/ImageDocument.cpp b/Source/WebCore/html/ImageDocument.cpp
index 8ecca70..f429223 100644
--- a/Source/WebCore/html/ImageDocument.cpp
+++ b/Source/WebCore/html/ImageDocument.cpp
@@ -49,6 +49,7 @@
 #include "RenderElement.h"
 #include "Settings.h"
 #include <wtf/IsoMallocInlines.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -273,7 +274,7 @@
 #if PLATFORM(IOS_FAMILY)
         FloatSize screenSize = page()->chrome().screenSize();
         if (imageSize.width() > screenSize.width())
-            processViewport(String::format("width=%u,viewport-fit=cover", static_cast<unsigned>(imageSize.width().toInt())), ViewportArguments::ImageDocument);
+            processViewport(makeString("width=", imageSize.width().toInt(), ",viewport-fit=cover"), ViewportArguments::ImageDocument);
 
         if (page())
             page()->chrome().client().imageOrMediaDocumentSizeChanged(IntSize(imageSize.width(), imageSize.height()));
diff --git a/Source/WebCore/html/parser/XSSAuditor.cpp b/Source/WebCore/html/parser/XSSAuditor.cpp
index 5eedb44..da9c333 100644
--- a/Source/WebCore/html/parser/XSSAuditor.cpp
+++ b/Source/WebCore/html/parser/XSSAuditor.cpp
@@ -45,7 +45,7 @@
 #include <wtf/ASCIICType.h>
 #include <wtf/MainThread.h>
 #include <wtf/NeverDestroyed.h>
-#include <wtf/text/StringView.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -332,7 +332,7 @@
             }
         }
         if (m_xssProtection == XSSProtectionDisposition::Invalid) {
-            document->addConsoleMessage(MessageSource::Security, MessageLevel::Error, "Error parsing header X-XSS-Protection: " + headerValue + ": "  + errorDetails + " at character position " + String::format("%u", errorPosition) + ". The default protections will be applied.");
+            document->addConsoleMessage(MessageSource::Security, MessageLevel::Error, makeString("Error parsing header X-XSS-Protection: ", headerValue, ": ", errorDetails, " at character position ", errorPosition, ". The default protections will be applied."));
             m_xssProtection = XSSProtectionDisposition::Enabled;
         }
 
diff --git a/Source/WebCore/inspector/InspectorFrontendClientLocal.cpp b/Source/WebCore/inspector/InspectorFrontendClientLocal.cpp
index a0c3887..243d849 100644
--- a/Source/WebCore/inspector/InspectorFrontendClientLocal.cpp
+++ b/Source/WebCore/inspector/InspectorFrontendClientLocal.cpp
@@ -205,7 +205,7 @@
 
 void InspectorFrontendClientLocal::setDockingUnavailable(bool unavailable)
 {
-    evaluateOnLoad(String::format("[\"setDockingUnavailable\", %s]", unavailable ? "true" : "false"));
+    evaluateOnLoad(makeString("[\"setDockingUnavailable\", ", unavailable ? "true" : "false", ']'));
 }
 
 void InspectorFrontendClientLocal::changeAttachedWindowHeight(unsigned height)
@@ -270,7 +270,7 @@
 
     m_dockSide = dockSide;
 
-    evaluateOnLoad(String::format("[\"setDockSide\", \"%s\"]", side));
+    evaluateOnLoad(makeString("[\"setDockSide\", \"", side, "\"]"));
 }
 
 void InspectorFrontendClientLocal::restoreAttachedWindowHeight()
@@ -294,7 +294,7 @@
 
 void InspectorFrontendClientLocal::setDebuggingEnabled(bool enabled)
 {
-    evaluateOnLoad(String::format("[\"setDebuggingEnabled\", %s]", enabled ? "true" : "false"));
+    evaluateOnLoad(makeString("[\"setDebuggingEnabled\", ", enabled ? "true" : "false", ']'));
 }
 
 bool InspectorFrontendClientLocal::isTimelineProfilingEnabled()
@@ -306,7 +306,7 @@
 
 void InspectorFrontendClientLocal::setTimelineProfilingEnabled(bool enabled)
 {
-    evaluateOnLoad(String::format("[\"setTimelineProfilingEnabled\", %s]", enabled ? "true" : "false"));
+    evaluateOnLoad(makeString("[\"setTimelineProfilingEnabled\", ", enabled ? "true" : "false", ']'));
 }
 
 bool InspectorFrontendClientLocal::isProfilingJavaScript()
@@ -339,7 +339,7 @@
 void InspectorFrontendClientLocal::showMainResourceForFrame(Frame* frame)
 {
     String frameId = m_inspectedPageController->pageAgent()->frameId(frame);
-    evaluateOnLoad(String::format("[\"showMainResourceForFrame\", \"%s\"]", frameId.ascii().data()));
+    evaluateOnLoad(makeString("[\"showMainResourceForFrame\", \"", frameId, "\"]"));
 }
 
 unsigned InspectorFrontendClientLocal::constrainedAttachedWindowHeight(unsigned preferredHeight, unsigned totalWindowHeight)
diff --git a/Source/WebCore/inspector/agents/InspectorCSSAgent.cpp b/Source/WebCore/inspector/agents/InspectorCSSAgent.cpp
index 4577652..d5a2274 100644
--- a/Source/WebCore/inspector/agents/InspectorCSSAgent.cpp
+++ b/Source/WebCore/inspector/agents/InspectorCSSAgent.cpp
@@ -62,8 +62,7 @@
 #include <wtf/Ref.h>
 #include <wtf/Vector.h>
 #include <wtf/text/CString.h>
-#include <wtf/text/StringConcatenate.h>
-
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -157,7 +156,7 @@
 
     String mergeId() final
     {
-        return String::format("SetStyleSheetText %s", m_styleSheet->id().utf8().data());
+        return "SetStyleSheetText " + m_styleSheet->id();
     }
 
     void merge(std::unique_ptr<Action> action) override
@@ -198,7 +197,7 @@
     String mergeId() override
     {
         ASSERT(m_styleSheet->id() == m_cssId.styleSheetId());
-        return String::format("SetStyleText %s:%u", m_styleSheet->id().utf8().data(), m_cssId.ordinal());
+        return makeString("SetStyleText ", m_styleSheet->id(), ':', m_cssId.ordinal());
     }
 
     void merge(std::unique_ptr<Action> action) override
diff --git a/Source/WebCore/inspector/agents/InspectorIndexedDBAgent.cpp b/Source/WebCore/inspector/agents/InspectorIndexedDBAgent.cpp
index 96bc87e..6d5881e 100644
--- a/Source/WebCore/inspector/agents/InspectorIndexedDBAgent.cpp
+++ b/Source/WebCore/inspector/agents/InspectorIndexedDBAgent.cpp
@@ -68,6 +68,7 @@
 #include <wtf/JSONValues.h>
 #include <wtf/NeverDestroyed.h>
 #include <wtf/Vector.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 using JSON::ArrayOf;
 using Inspector::Protocol::IndexedDB::DatabaseWithObjectStores;
@@ -711,7 +712,7 @@
             auto result = idbObjectStore->clear(*exec);
             ASSERT(!result.hasException());
             if (result.hasException()) {
-                m_requestCallback->sendFailure(String::format("Could not clear object store '%s': %d", m_objectStoreName.utf8().data(), result.releaseException().code()));
+                m_requestCallback->sendFailure(makeString("Could not clear object store '", m_objectStoreName, "': ", static_cast<int>(result.releaseException().code())));
                 return;
             }
             idbRequest = result.releaseReturnValue();
diff --git a/Source/WebCore/page/MemoryRelease.cpp b/Source/WebCore/page/MemoryRelease.cpp
index 08f04a4..1f5f633 100644
--- a/Source/WebCore/page/MemoryRelease.cpp
+++ b/Source/WebCore/page/MemoryRelease.cpp
@@ -169,7 +169,7 @@
             continue;
         String tagName = displayNameForVMTag(i);
         if (!tagName)
-            tagName = String::format("Tag %u", i);
+            tagName = makeString("Tag ", i);
         RELEASE_LOG(MemoryPressure, "%16s: %lu MB", tagName.latin1().data(), dirty / MB);
     }
 #endif
diff --git a/Source/WebCore/page/cocoa/ResourceUsageOverlayCocoa.mm b/Source/WebCore/page/cocoa/ResourceUsageOverlayCocoa.mm
index 4b5c631..fdf4a23 100644
--- a/Source/WebCore/page/cocoa/ResourceUsageOverlayCocoa.mm
+++ b/Source/WebCore/page/cocoa/ResourceUsageOverlayCocoa.mm
@@ -431,7 +431,7 @@
         return String::format("%.2f MB", static_cast<double>(number) / 1048576);
     if (number >= 1024)
         return String::format("%.1f kB", static_cast<double>(number) / 1024);
-    return String::format("%lu", number);
+    return String::number(number);
 }
 
 static String gcTimerString(MonotonicTime timerFireDate, MonotonicTime now)
@@ -469,9 +469,9 @@
         
         String label = String::format("% 11s: %s", category.name.ascii().data(), formatByteNumber(dirty).ascii().data());
         if (external)
-            label = label + String::format(" + %s", formatByteNumber(external).ascii().data());
+            label = label + makeString(" + ", formatByteNumber(external));
         if (reclaimable)
-            label = label + String::format(" [%s]", formatByteNumber(reclaimable).ascii().data());
+            label = label + makeString(" [", formatByteNumber(reclaimable), ']');
 
         // FIXME: Show size/capacity of GC heap.
         showText(context, 10, y, category.color.get(), label);
@@ -480,8 +480,8 @@
     y -= 5;
 
     MonotonicTime now = MonotonicTime::now();
-    showText(context, 10, y + 10, colorForLabels, String::format("    Eden GC: %s", gcTimerString(data.timeOfNextEdenCollection, now).ascii().data()));
-    showText(context, 10, y + 20, colorForLabels, String::format("    Full GC: %s", gcTimerString(data.timeOfNextFullCollection, now).ascii().data()));
+    showText(context, 10, y + 10, colorForLabels, "    Eden GC: " + gcTimerString(data.timeOfNextEdenCollection, now));
+    showText(context, 10, y + 20, colorForLabels, "    Full GC: " + gcTimerString(data.timeOfNextFullCollection, now));
 
     drawCpuHistory(context, viewBounds.size.width - 70, 0, viewBounds.size.height, data.cpu);
     drawGCHistory(context, viewBounds.size.width - 140, 0, viewBounds.size.height, data.gcHeapSize, data.categories[MemoryCategory::GCHeap].dirtySize);
diff --git a/Source/WebCore/page/cocoa/ResourceUsageThreadCocoa.mm b/Source/WebCore/page/cocoa/ResourceUsageThreadCocoa.mm
index d8e54be..8956172 100644
--- a/Source/WebCore/page/cocoa/ResourceUsageThreadCocoa.mm
+++ b/Source/WebCore/page/cocoa/ResourceUsageThreadCocoa.mm
@@ -36,6 +36,7 @@
 #include <mach/vm_statistics.h>
 #include <pal/spi/cocoa/MachVMSPI.h>
 #include <wtf/MachSendRight.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -63,7 +64,7 @@
             continue;
         String tagName = displayNameForVMTag(i);
         if (!tagName)
-            tagName = String::format("Tag %u", i);
+            tagName = makeString("Tag ", i);
         WTFLogAlways("  %02X %16s %10ld %10ld %10ld",
             i,
             tagName.ascii().data(),
diff --git a/Source/WebCore/platform/animation/TimingFunction.cpp b/Source/WebCore/platform/animation/TimingFunction.cpp
index cfd0b36..9407342 100644
--- a/Source/WebCore/platform/animation/TimingFunction.cpp
+++ b/Source/WebCore/platform/animation/TimingFunction.cpp
@@ -30,6 +30,7 @@
 #include "SpringSolver.h"
 #include "StyleProperties.h"
 #include "UnitBezier.h"
+#include <wtf/text/StringConcatenateNumbers.h>
 #include <wtf/text/TextStream.h>
 
 namespace WebCore {
@@ -181,7 +182,7 @@
     if (m_type == TimingFunction::StepsFunction) {
         auto& function = downcast<StepsTimingFunction>(*this);
         if (!function.stepAtStart())
-            return String::format("steps(%d)", function.numberOfSteps());
+            return makeString("steps(", function.numberOfSteps(), ')');
     }
 
     TextStream stream;
diff --git a/Source/WebCore/platform/graphics/avfoundation/AVTrackPrivateAVFObjCImpl.mm b/Source/WebCore/platform/graphics/avfoundation/AVTrackPrivateAVFObjCImpl.mm
index 6e48fda..eb69888 100644
--- a/Source/WebCore/platform/graphics/avfoundation/AVTrackPrivateAVFObjCImpl.mm
+++ b/Source/WebCore/platform/graphics/avfoundation/AVTrackPrivateAVFObjCImpl.mm
@@ -180,7 +180,7 @@
 AtomicString AVTrackPrivateAVFObjCImpl::id() const
 {
     if (m_assetTrack)
-        return String::format("%d", [m_assetTrack trackID]);
+        return AtomicString::number([m_assetTrack trackID]);
     if (m_mediaSelectionOption)
         return [[m_mediaSelectionOption->avMediaSelectionOption() optionID] stringValue];
     ASSERT_NOT_REACHED();
diff --git a/Source/WebCore/platform/graphics/avfoundation/objc/MediaSampleAVFObjC.h b/Source/WebCore/platform/graphics/avfoundation/objc/MediaSampleAVFObjC.h
index 60ee96f..966ccd5 100644
--- a/Source/WebCore/platform/graphics/avfoundation/objc/MediaSampleAVFObjC.h
+++ b/Source/WebCore/platform/graphics/avfoundation/objc/MediaSampleAVFObjC.h
@@ -84,7 +84,7 @@
     }
     MediaSampleAVFObjC(CMSampleBufferRef sample, int trackID)
         : m_sample(sample)
-        , m_id(String::format("%d", trackID))
+        , m_id(AtomicString::number(trackID))
     {
     }
     MediaSampleAVFObjC(CMSampleBufferRef sample, VideoRotation rotation, bool mirrored)
diff --git a/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp b/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp
index e4f67cd..97788fa 100644
--- a/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp
+++ b/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp
@@ -52,8 +52,8 @@
 #include <wtf/NeverDestroyed.h>
 #include <wtf/SetForScope.h>
 #include <wtf/SystemTracing.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 #include <wtf/text/TextStream.h>
-#include <wtf/text/WTFString.h>
 
 #if PLATFORM(IOS_FAMILY)
 #include "SystemMemory.h"
@@ -1101,7 +1101,7 @@
             m_contentsLayerPurpose = ContentsLayerPurpose::BackgroundColor;
             m_contentsLayer = createPlatformCALayer(PlatformCALayer::LayerTypeLayer, this);
 #if ENABLE(TREE_DEBUGGING)
-            m_contentsLayer->setName(String::format("contents color %llu", m_contentsLayer->layerID()));
+            m_contentsLayer->setName(makeString("contents color ", m_contentsLayer->layerID()));
 #else
             m_contentsLayer->setName("contents color");
 #endif
@@ -2566,7 +2566,7 @@
         if (!m_contentsLayer.get()) {
             m_contentsLayer = createPlatformCALayer(PlatformCALayer::LayerTypeLayer, this);
 #if ENABLE(TREE_DEBUGGING)
-            m_contentsLayer->setName(String::format("contents image %llu", m_contentsLayer->layerID()));
+            m_contentsLayer->setName(makeString("contents image ", m_contentsLayer->layerID()));
 #else
             m_contentsLayer->setName("contents image");
 #endif
@@ -2672,7 +2672,7 @@
             m_contentsClippingLayer = createPlatformCALayer(PlatformCALayer::LayerTypeLayer, this);
             m_contentsClippingLayer->setAnchorPoint(FloatPoint());
 #if ENABLE(TREE_DEBUGGING)
-            m_contentsClippingLayer->setName(String::format("contents clipping %llu", m_contentsClippingLayer->layerID()));
+            m_contentsClippingLayer->setName(makeString("contents clipping ", m_contentsClippingLayer->layerID()));
 #else
             m_contentsClippingLayer->setName("contents clipping");
 #endif
@@ -3156,7 +3156,7 @@
     for (int internalFilterPropertyIndex = 0; internalFilterPropertyIndex < numAnimatedProperties; ++internalFilterPropertyIndex) {
         bool valuesOK;
         RefPtr<PlatformCAAnimation> caAnimation;
-        String keyPath = String::format("filters.filter_%d.%s", animationIndex, PlatformCAFilters::animatedFilterPropertyName(filterOp, internalFilterPropertyIndex));
+        String keyPath = makeString("filters.filter_", animationIndex, '.', PlatformCAFilters::animatedFilterPropertyName(filterOp, internalFilterPropertyIndex));
         
         if (isKeyframe) {
             caAnimation = createKeyframeAnimation(animation, keyPath, false);
@@ -3914,7 +3914,7 @@
     } else {
         resultLayer = cloneLayer(sourceLayer, cloneLevel);
 #if ENABLE(TREE_DEBUGGING)
-        resultLayer->setName(String::format("clone %d of %llu", cloneID[0U], sourceLayer->layerID()));
+        resultLayer->setName(makeString("clone ", cloneID[0U], " of ", sourceLayer->layerID()));
 #else
         resultLayer->setName("clone of " + m_name);
 #endif
diff --git a/Source/WebCore/platform/mock/MockRealtimeVideoSource.cpp b/Source/WebCore/platform/mock/MockRealtimeVideoSource.cpp
index 1ff6c30..a48e14f 100644
--- a/Source/WebCore/platform/mock/MockRealtimeVideoSource.cpp
+++ b/Source/WebCore/platform/mock/MockRealtimeVideoSource.cpp
@@ -44,7 +44,7 @@
 #include "RealtimeMediaSourceSettings.h"
 #include <math.h>
 #include <wtf/UUID.h>
-#include <wtf/text/StringView.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -367,12 +367,12 @@
 
     auto size = this->size();
     statsLocation.move(0, m_statsFontSize);
-    string = String::format("Size: %u x %u", size.width(), size.height());
+    string = makeString("Size: ", size.width(), " x ", size.height());
     context.drawText(statsFont, TextRun((StringView(string))), statsLocation);
 
     if (mockCamera()) {
         statsLocation.move(0, m_statsFontSize);
-        string = String::format("Preset size: %u x %u", captureSize.width(), captureSize.height());
+        string = makeString("Preset size: ", captureSize.width(), " x ", captureSize.height());
         context.drawText(statsFont, TextRun((StringView(string))), statsLocation);
 
         const char* camera;
@@ -393,7 +393,7 @@
             camera = "Unknown";
             break;
         }
-        string = String::format("Camera: %s", camera);
+        string = makeString("Camera: ", camera);
         statsLocation.move(0, m_statsFontSize);
         context.drawText(statsFont, TextRun((StringView(string))), statsLocation);
     } else if (!name().isNull()) {
diff --git a/Source/WebCore/platform/mock/mediasource/MockSourceBufferPrivate.cpp b/Source/WebCore/platform/mock/mediasource/MockSourceBufferPrivate.cpp
index 9fbac00..ce273f1 100644
--- a/Source/WebCore/platform/mock/mediasource/MockSourceBufferPrivate.cpp
+++ b/Source/WebCore/platform/mock/mediasource/MockSourceBufferPrivate.cpp
@@ -49,7 +49,7 @@
 private:
     MockMediaSample(const MockSampleBox& box)
         : m_box(box)
-        , m_id(String::format("%d", box.trackID()))
+        , m_id(String::number(box.trackID()))
     {
     }
 
diff --git a/Source/WebCore/platform/network/ParsedContentRange.cpp b/Source/WebCore/platform/network/ParsedContentRange.cpp
index 00b90c4..a3d4f04 100644
--- a/Source/WebCore/platform/network/ParsedContentRange.cpp
+++ b/Source/WebCore/platform/network/ParsedContentRange.cpp
@@ -27,7 +27,7 @@
 #include "ParsedContentRange.h"
 
 #include <wtf/StdLibExtras.h>
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -127,8 +127,8 @@
     if (!m_isValid)
         return String();
     if (m_instanceLength == UnknownLength)
-        return String::format("bytes %" PRId64 "-%" PRId64 "/*", m_firstBytePosition, m_lastBytePosition);
-    return String::format("bytes %" PRId64 "-%" PRId64 "/%" PRId64, m_firstBytePosition, m_lastBytePosition, m_instanceLength);
+        return makeString("bytes ", m_firstBytePosition, '-', m_lastBytePosition, "/*");
+    return makeString("bytes ", m_firstBytePosition, '-', m_lastBytePosition, '/', m_instanceLength);
 }
 
 }
diff --git a/Source/WebCore/platform/network/cf/NetworkStorageSessionCFNet.cpp b/Source/WebCore/platform/network/cf/NetworkStorageSessionCFNet.cpp
index 09d86d0..b01a7e6 100644
--- a/Source/WebCore/platform/network/cf/NetworkStorageSessionCFNet.cpp
+++ b/Source/WebCore/platform/network/cf/NetworkStorageSessionCFNet.cpp
@@ -30,6 +30,7 @@
 #include <wtf/NeverDestroyed.h>
 #include <wtf/ProcessID.h>
 #include <wtf/ProcessPrivilege.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 #if PLATFORM(COCOA)
 #include "PublicSuffix.h"
diff --git a/Source/WebCore/platform/sql/SQLiteDatabase.cpp b/Source/WebCore/platform/sql/SQLiteDatabase.cpp
index 663e0bc..d7bc613 100644
--- a/Source/WebCore/platform/sql/SQLiteDatabase.cpp
+++ b/Source/WebCore/platform/sql/SQLiteDatabase.cpp
@@ -46,8 +46,7 @@
 static void unauthorizedSQLFunction(sqlite3_context *context, int, sqlite3_value **)
 {
     const char* functionName = (const char*)sqlite3_user_data(context);
-    String errorMessage = String::format("Function %s is unauthorized", functionName);
-    sqlite3_result_error(context, errorMessage.utf8().data(), -1);
+    sqlite3_result_error(context, makeString("Function ", functionName, " is unauthorized").utf8().data(), -1);
 }
 
 static void initializeSQLiteIfNecessary()
diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
index 5b1ca4c..88bc5d1 100644
--- a/Source/WebCore/rendering/RenderLayerCompositor.cpp
+++ b/Source/WebCore/rendering/RenderLayerCompositor.cpp
@@ -1278,7 +1278,7 @@
         backing->backingStoreMemoryEstimate() / 1024));
     
     if (!layer.renderer().style().hasAutoZIndex())
-        logString.append(String::format(" z-index: %d", layer.renderer().style().zIndex())); 
+        logString.append(makeString(" z-index: ", layer.renderer().style().zIndex()));
 
     logString.appendLiteral(" (");
     logString.append(logReasonsForCompositing(layer));
diff --git a/Source/WebCore/workers/service/server/RegistrationDatabase.cpp b/Source/WebCore/workers/service/server/RegistrationDatabase.cpp
index 1af4378..56dd9bc 100644
--- a/Source/WebCore/workers/service/server/RegistrationDatabase.cpp
+++ b/Source/WebCore/workers/service/server/RegistrationDatabase.cpp
@@ -45,6 +45,7 @@
 #include <wtf/persistence/PersistentCoders.h>
 #include <wtf/persistence/PersistentDecoder.h>
 #include <wtf/persistence/PersistentEncoder.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebCore {
 
@@ -201,7 +202,7 @@
         // If there is no Records table at all, create it and then bail.
         if (sqliteResult == SQLITE_DONE) {
             if (!m_database->executeCommand(recordsTableSchema()))
-                return String::format("Could not create Records table in database (%i) - %s", m_database->lastError(), m_database->lastErrorMsg());
+                return makeString("Could not create Records table in database (", m_database->lastError(), ") - ", m_database->lastErrorMsg());
             return { };
         }
 
@@ -359,7 +360,7 @@
 
     SQLiteStatement sql(*m_database, "SELECT * FROM Records;"_s);
     if (sql.prepare() != SQLITE_OK)
-        return String::format("Failed to prepare statement to retrieve registrations from records table (%i) - %s", m_database->lastError(), m_database->lastErrorMsg());
+        return makeString("Failed to prepare statement to retrieve registrations from records table (", m_database->lastError(), ") - ", m_database->lastErrorMsg());
 
     int result = sql.step();
 
@@ -411,7 +412,7 @@
     }
 
     if (result != SQLITE_DONE)
-        return String::format("Failed to import at least one registration from records table (%i) - %s", m_database->lastError(), m_database->lastErrorMsg());
+        return makeString("Failed to import at least one registration from records table (", m_database->lastError(), ") - ", m_database->lastErrorMsg());
 
     return { };
 }
diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
index 0ff7b88..d93f922 100644
--- a/Source/WebKit/ChangeLog
+++ b/Source/WebKit/ChangeLog
@@ -1,3 +1,22 @@
+2018-12-15  Darin Adler  <darin@apple.com>
+
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        * Shared/WebMemorySampler.cpp:
+        (WebKit::WebMemorySampler::writeHeaders): Use makeString.
+
+        * UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm:
+        (WebKit::LocalAuthenticator::makeCredential): Use string concatentation.
+
+        * UIProcess/WebInspectorUtilities.cpp:
+        (WebKit::inspectorPageGroupIdentifierForPage): Use makeString.
+        * UIProcess/WebProcessPool.cpp:
+        (WebKit::WebProcessPool::processDidFinishLaunching): Ditto.
+        (WebKit::WebProcessPool::startMemorySampler): Ditto.
+
 2019-01-27  Jiewen Tan  <jiewen_tan@apple.com>
 
         Use a load optimizer for some sites
diff --git a/Source/WebKit/Shared/WebMemorySampler.cpp b/Source/WebKit/Shared/WebMemorySampler.cpp
index 2b85200..87e6eeb 100644
--- a/Source/WebKit/Shared/WebMemorySampler.cpp
+++ b/Source/WebKit/Shared/WebMemorySampler.cpp
@@ -32,6 +32,7 @@
 #include <wtf/ProcessID.h>
 #include <wtf/text/CString.h>
 #include <wtf/text/StringBuilder.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebKit {
 using namespace WebCore;
@@ -142,7 +143,7 @@
 
 void WebMemorySampler::writeHeaders()
 {
-    String processDetails = String::format("Process: %s Pid: %d\n", processName().utf8().data(), getCurrentProcessID());
+    String processDetails = makeString("Process: ", processName(), " Pid: ", getCurrentProcessID(), '\n');
 
     CString utf8String = processDetails.utf8();
     FileSystem::writeToFile(m_sampleLogFile, utf8String.data(), utf8String.length());
diff --git a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm
index efc3e16..9c27727 100644
--- a/Source/WebKit/UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm
+++ b/Source/WebKit/UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm
@@ -152,7 +152,7 @@
         weakThis->continueMakeCredentialAfterUserConsented(consent);
     };
     m_connection->getUserConsent(
-        String::format("Allow %s to create a public key credential for %s", requestData().creationOptions.rp.id.utf8().data(), requestData().creationOptions.user.name.utf8().data()),
+        "Allow " + requestData().creationOptions.rp.id + " to create a public key credential for " + requestData().creationOptions.user.name,
         WTFMove(callback));
 #endif // !PLATFORM(IOS_FAMILY)
 }
diff --git a/Source/WebKit/UIProcess/WebInspectorUtilities.cpp b/Source/WebKit/UIProcess/WebInspectorUtilities.cpp
index c5db401..3b49ce0 100644
--- a/Source/WebKit/UIProcess/WebInspectorUtilities.cpp
+++ b/Source/WebKit/UIProcess/WebInspectorUtilities.cpp
@@ -33,6 +33,7 @@
 #include "WebProcessProxy.h"
 #include <wtf/HashMap.h>
 #include <wtf/NeverDestroyed.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WebKit {
 
@@ -57,7 +58,7 @@
 
 String inspectorPageGroupIdentifierForPage(WebPageProxy* page)
 {
-    return String::format("__WebInspectorPageGroupLevel%u__", inspectorLevelForPage(page));
+    return makeString("__WebInspectorPageGroupLevel", inspectorLevelForPage(page), "__");
 }
 
 void trackInspectorPage(WebPageProxy* page)
diff --git a/Source/WebKit/UIProcess/WebProcessPool.cpp b/Source/WebKit/UIProcess/WebProcessPool.cpp
index d2f6a67..9e64800 100644
--- a/Source/WebKit/UIProcess/WebProcessPool.cpp
+++ b/Source/WebKit/UIProcess/WebProcessPool.cpp
@@ -41,9 +41,6 @@
 #include "DownloadProxyMessages.h"
 #include "GamepadData.h"
 #include "HighPerformanceGraphicsUsageSampler.h"
-#if ENABLE(LEGACY_CUSTOM_PROTOCOL_MANAGER)
-#include "LegacyCustomProtocolManagerMessages.h"
-#endif
 #include "LogInitialization.h"
 #include "Logging.h"
 #include "NetworkProcessCreationParameters.h"
@@ -98,6 +95,11 @@
 #include <wtf/URLParser.h>
 #include <wtf/WallTime.h>
 #include <wtf/text/StringBuilder.h>
+#include <wtf/text/StringConcatenateNumbers.h>
+
+#if ENABLE(LEGACY_CUSTOM_PROTOCOL_MANAGER)
+#include "LegacyCustomProtocolManagerMessages.h"
+#endif
 
 #if ENABLE(SERVICE_CONTROLS)
 #include "ServicesController.h"
@@ -1019,7 +1021,7 @@
     if (m_memorySamplerEnabled) {
         SandboxExtension::Handle sampleLogSandboxHandle;        
         WallTime now = WallTime::now();
-        String sampleLogFilePath = String::format("WebProcess%llupid%d", static_cast<unsigned long long>(now.secondsSinceEpoch().seconds()), process->processIdentifier());
+        String sampleLogFilePath = makeString("WebProcess", static_cast<unsigned long long>(now.secondsSinceEpoch().seconds()), "pid", process->processIdentifier());
         sampleLogFilePath = SandboxExtension::createHandleForTemporaryFile(sampleLogFilePath, SandboxExtension::Type::ReadWrite, sampleLogSandboxHandle);
         
         process->send(Messages::WebProcess::StartMemorySampler(sampleLogSandboxHandle, sampleLogFilePath, m_memorySamplerInterval), 0);
@@ -1577,7 +1579,7 @@
     // For WebProcess
     SandboxExtension::Handle sampleLogSandboxHandle;    
     WallTime now = WallTime::now();
-    String sampleLogFilePath = String::format("WebProcess%llu", static_cast<unsigned long long>(now.secondsSinceEpoch().seconds()));
+    String sampleLogFilePath = makeString("WebProcess", static_cast<unsigned long long>(now.secondsSinceEpoch().seconds()));
     sampleLogFilePath = SandboxExtension::createHandleForTemporaryFile(sampleLogFilePath, SandboxExtension::Type::ReadWrite, sampleLogSandboxHandle);
     
     sendToAllProcesses(Messages::WebProcess::StartMemorySampler(sampleLogSandboxHandle, sampleLogFilePath, interval));
diff --git a/Source/WebKitLegacy/ChangeLog b/Source/WebKitLegacy/ChangeLog
index a6a58c4..d9590d8 100644
--- a/Source/WebKitLegacy/ChangeLog
+++ b/Source/WebKitLegacy/ChangeLog
@@ -1,3 +1,22 @@
+2019-01-26  Darin Adler  <darin@apple.com>
+  
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        * Shared/WebMemorySampler.cpp:
+        (WebKit::WebMemorySampler::writeHeaders): Use makeString.
+
+        * UIProcess/WebAuthentication/Cocoa/LocalAuthenticator.mm:
+        (WebKit::LocalAuthenticator::makeCredential): Use string concatentation.
+
+        * UIProcess/WebInspectorUtilities.cpp:
+        (WebKit::inspectorPageGroupIdentifierForPage): Use makeString.
+        * UIProcess/WebProcessPool.cpp:
+        (WebKit::WebProcessPool::processDidFinishLaunching): Ditto.
+        (WebKit::WebProcessPool::startMemorySampler): Ditto.
+
 2019-01-24  Ross Kirsling  <ross.kirsling@sony.com>
 
         Move FileSystem to WTF
diff --git a/Source/WebKitLegacy/WebCoreSupport/NetworkStorageSessionMap.cpp b/Source/WebKitLegacy/WebCoreSupport/NetworkStorageSessionMap.cpp
index 470796a..584f0a1 100644
--- a/Source/WebKitLegacy/WebCoreSupport/NetworkStorageSessionMap.cpp
+++ b/Source/WebKitLegacy/WebCoreSupport/NetworkStorageSessionMap.cpp
@@ -30,6 +30,7 @@
 #include <wtf/MainThread.h>
 #include <wtf/ProcessID.h>
 #include <wtf/ProcessPrivilege.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 static std::unique_ptr<WebCore::NetworkStorageSession>& defaultNetworkStorageSession()
 {
@@ -67,7 +68,7 @@
 {
 #if PLATFORM(COCOA) || USE(CFURLCONNECTION)
     // Session name should be short enough for shared memory region name to be under the limit, otehrwise sandbox rules won't work (see <rdar://problem/13642852>).
-    String sessionName = String::format("WebKit Test-%u", static_cast<uint32_t>(getCurrentProcessID()));
+    String sessionName = makeString("WebKit Test-", getCurrentProcessID());
 
     auto session = adoptCF(WebCore::createPrivateStorageSession(sessionName.createCFString().get()));
 
diff --git a/Tools/ChangeLog b/Tools/ChangeLog
index 01cb3b9..7f994b5 100644
--- a/Tools/ChangeLog
+++ b/Tools/ChangeLog
@@ -1,3 +1,16 @@
+2018-12-15  Darin Adler  <darin@apple.com>
+
+        Replace many uses of String::format with more type-safe alternatives
+        https://bugs.webkit.org/show_bug.cgi?id=192742
+
+        Reviewed by Mark Lam.
+
+        * WebKitTestRunner/InjectedBundle/TestRunner.cpp:
+        (WTR::cacheTestRunnerCallback): Use makeString.
+        * WebKitTestRunner/TestController.cpp:
+        (WTR::TestController::didReceiveAuthenticationChallenge): Use makeString.
+        (WTR::TestController::downloadDidFail): Use an ASCIILiteral via the _s syntax.
+
 2019-01-27  Jiewen Tan  <jiewen_tan@apple.com>
 
         Use a load optimizer for some sites
diff --git a/Tools/WebKitTestRunner/InjectedBundle/TestRunner.cpp b/Tools/WebKitTestRunner/InjectedBundle/TestRunner.cpp
index 40d4129..100ab7c 100644
--- a/Tools/WebKitTestRunner/InjectedBundle/TestRunner.cpp
+++ b/Tools/WebKitTestRunner/InjectedBundle/TestRunner.cpp
@@ -55,6 +55,7 @@
 #include <wtf/StdLibExtras.h>
 #include <wtf/text/CString.h>
 #include <wtf/text/StringBuilder.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 namespace WTR {
 
@@ -813,7 +814,7 @@
         return;
 
     if (callbackMap().contains(index)) {
-        InjectedBundle::singleton().outputText(String::format("FAIL: Tried to install a second TestRunner callback for the same event (id %d)\n\n", index));
+        InjectedBundle::singleton().outputText(makeString("FAIL: Tried to install a second TestRunner callback for the same event (id ", index, ")\n\n"));
         return;
     }
 
diff --git a/Tools/WebKitTestRunner/TestController.cpp b/Tools/WebKitTestRunner/TestController.cpp
index 7b662aa..0cff719 100644
--- a/Tools/WebKitTestRunner/TestController.cpp
+++ b/Tools/WebKitTestRunner/TestController.cpp
@@ -78,7 +78,7 @@
 #include <wtf/SetForScope.h>
 #include <wtf/UUID.h>
 #include <wtf/text/CString.h>
-#include <wtf/text/WTFString.h>
+#include <wtf/text/StringConcatenateNumbers.h>
 
 #if PLATFORM(COCOA)
 #include <WebKit/WKContextPrivateMac.h>
@@ -2073,11 +2073,11 @@
 
     std::string host = toSTD(adoptWK(WKProtectionSpaceCopyHost(protectionSpace)).get());
     int port = WKProtectionSpaceGetPort(protectionSpace);
-    String message = String::format("%s:%d - didReceiveAuthenticationChallenge - %s - ", host.c_str(), port, toString(authenticationScheme));
+    String message = makeString(host.c_str(), ':', port, " - didReceiveAuthenticationChallenge - ", toString(authenticationScheme), " - ");
     if (!m_handlesAuthenticationChallenges)
         message.append("Simulating cancelled authentication sheet\n");
     else
-        message.append(String::format("Responding with %s:%s\n", m_authenticationUsername.utf8().data(), m_authenticationPassword.utf8().data()));
+        message.append("Responding with " + m_authenticationUsername + ":" + m_authenticationPassword + "\n");
     m_currentInvocation->outputText(message);
 
     if (!m_handlesAuthenticationChallenges) {
@@ -2175,8 +2175,7 @@
 void TestController::downloadDidFail(WKContextRef, WKDownloadRef, WKErrorRef error)
 {
     if (m_shouldLogDownloadCallbacks) {
-        String message = String::format("Download failed.\n");
-        m_currentInvocation->outputText(message);
+        m_currentInvocation->outputText("Download failed.\n"_s);
 
         WKRetainPtr<WKStringRef> errorDomain = adoptWK(WKErrorCopyDomain(error));
         WKRetainPtr<WKStringRef> errorDescription = adoptWK(WKErrorCopyLocalizedDescription(error));