144378 2015-04-28 23:57:50 -0700 LazyNeverDestroyed is not thread safe in debug builds, causing assertions 2025-08-26 05:23:37 -0700 1 1 1 Unclassified WebKit Web Template Framework 528+ (Nightly build) Unspecified Unspecified RESOLVED FIXED P2 Normal --- 1 ap ap andersca benjamin cdumez cmarcelo commit-queue kling zan zimmermann oldest_to_newest 1089910 0 ap 2015-04-28 23:57:50 -0700 Thread 28 Crashed:: WebCore: Worker 0 com.apple.JavaScriptCore 0x00000001128509da WTFCrash + 42 (Assertions.cpp:321) ASSERT(m_isConstructed); 1 com.apple.JavaScriptCore 0x0000000112862ed2 WTF::LazyNeverDestroyed<std::__1::mutex>::asPtr() + 66 (NeverDestroyed.h:102) 2 com.apple.JavaScriptCore 0x0000000112862e85 WTF::LazyNeverDestroyed<std::__1::mutex>::operator std::__1::mutex&() + 21 (NeverDestroyed.h:94) 3 com.apple.JavaScriptCore 0x0000000112862161 WTF::cachedCollatorMutex() + 577 (CollatorICU.cpp:62) 4 com.apple.JavaScriptCore 0x0000000112861c8b WTF::Collator::Collator(char const*, bool) + 43 (CollatorICU.cpp:120) 5 com.apple.JavaScriptCore 0x0000000112861c4c WTF::Collator::Collator(char const*, bool) + 44 (CollatorICU.cpp:146) 6 com.apple.JavaScriptCore 0x0000000112788a4b JSC::stringProtoFuncLocaleCompare(JSC::ExecState*) + 155 (StringPrototype.cpp:1429) LazyNeverDestroyed has a non-trivial constructor in debug builds, which is obviously wrong to have for the pattern we normally use it with. static std::mutex& cachedCollatorMutex() { static std::once_flag onceFlag; static LazyNeverDestroyed<std::mutex> mutex; std::call_once(onceFlag, []{ mutex.construct(); }); return mutex; } 1089940 1 zan 2015-04-29 02:40:36 -0700 Removing the brace initializer for the m_isConstructed member will make it trivial again. 1090044 2 ap 2015-04-29 10:09:02 -0700 Yes, this class is only used for static variables. I don't know of a way to assert that though. 1090123 3 251979 ap 2015-04-29 12:39:23 -0700 Created attachment 251979 proposed fix 1090326 4 251979 commit-queue 2015-04-29 20:06:53 -0700 Comment on attachment 251979 proposed fix Clearing flags on attachment: 251979 Committed r183608: <http://trac.webkit.org/changeset/183608> 1090327 5 commit-queue 2015-04-29 20:07:03 -0700 All reviewed patches have been landed. Closing bug. 2138785 6 zimmermann 2025-08-26 05:23:37 -0700 10 years later this has hit me: ``` Yes, this class is only used for static variables. I don't know of a way to assert that though. ``` I'm building WebKit with gcc-14, and it complains: ``` unified-sources/UnifiedSource-2f84417a-14.cpp In file included from /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/MallocCommon.h:28, from /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/FastMalloc.h:26, from /host/home/nzimmermann/Software/GitRepositories/WebKit/Source/WebCore/config.h:47, from /host/home/nzimmermann/Software/GitRepositories/WebKit/Source/WebCore/css/CSSValue.cpp:29, from /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WebCore/DerivedSources/unified-sources/UnifiedSource-2f84417a-14.cpp:1: In member function ‘void WTF::LazyNeverDestroyed< <template-parameter-1-1>, <template-parameter-1-2> >::constructWithoutAccessCheck(Args&& ...) [with Args = {WebCore::CSSValue::StaticCSSValueTag, WebCore::CSSPrimitiveValue::ImplicitInitialValueTag}; T = WebCore::CSSPrimitiveValue; AccessTraits = WTF::AnyThreadsAccessTraits]’, inlined from ‘void WTF::LazyNeverDestroyed< <template-parameter-1-1>, <template-parameter-1-2> >::construct(Args&& ...) [with Args = {WebCore::CSSValue::StaticCSSValueTag, WebCore::CSSPrimitiveValue::ImplicitInitialValueTag}; T = WebCore::CSSPrimitiveValue; AccessTraits = WTF::AnyThreadsAccessTraits]’ at /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/NeverDestroyed.h:128:36, inlined from ‘WebCore::StaticCSSValuePool::StaticCSSValuePool()’ at /host/home/nzimmermann/Software/GitRepositories/WebKit/Source/WebCore/css/CSSValuePool.cpp:41:37: /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/NeverDestroyed.h:134:17: error: ‘*(WTF::LazyNeverDestroyed<WebCore::CSSPrimitiveValue, WTF::AnyThreadsAccessTraits>*)this.WTF::LazyNeverDestroyed<WebCore::CSSPrimitiveValue>::m_isConstructed’ is used uninitialized [-Werror=uninitialized] 134 | ASSERT(!m_isConstructed); | ^~~~~~~~~~~~~~~ /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/Assertions.h:384:58: note: in definition of macro ‘UNLIKELY_FOR_C_ASSERTIONS’ 384 | #define UNLIKELY_FOR_C_ASSERTIONS(x) __builtin_expect(!!(x), 0) | ^ /host/home/nzimmermann/Software/GitRepositories/WebKit/WebKitBuild/WPE/Release/WTF/Headers/wtf/NeverDestroyed.h:134:9: note: in expansion of macro ‘ASSERT’ 134 | ASSERT(!m_isConstructed); | ^~~~~~ cc1plus: all warnings being treated as errors ``` That is because (Static)CSSValuePool is actually using non-static LazyNeverDestroyed objects (stored as members). While StaticCSSValuePool - as the name implies - is static itself, its members aren't and gcc caught that. Any ideas? 251979 2015-04-29 12:39:23 -0700 2015-04-29 20:06:53 -0700 proposed fix LazyNeverDestroyed.txt text/plain 1128 ap SW5kZXg6IFNvdXJjZS9XVEYvQ2hhbmdlTG9nCj09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIFNvdXJjZS9XVEYvQ2hh bmdlTG9nCShyZXZpc2lvbiAxODM1NjYpCisrKyBTb3VyY2UvV1RGL0NoYW5nZUxvZwkod29ya2lu ZyBjb3B5KQpAQCAtMSwzICsxLDEyIEBACisyMDE1LTA0LTI5ICBBbGV4ZXkgUHJvc2t1cnlha292 ICA8YXBAYXBwbGUuY29tPgorCisgICAgICAgIExhenlOZXZlckRlc3Ryb3llZCBpcyBub3QgdGhy ZWFkIHNhZmUgaW4gZGVidWcgYnVpbGRzLCBjYXVzaW5nIGFzc2VydGlvbnMKKyAgICAgICAgaHR0 cHM6Ly9idWdzLndlYmtpdC5vcmcvc2hvd19idWcuY2dpP2lkPTE0NDM3OAorCisgICAgICAgIFJl dmlld2VkIGJ5IE5PQk9EWSAoT09QUyEpLgorCisgICAgICAgICogd3RmL05ldmVyRGVzdHJveWVk Lmg6CisKIDIwMTUtMDQtMjkgIE15bGVzIEMuIE1heGZpZWxkICA8bW1heGZpZWxkQGFwcGxlLmNv bT4KIAogICAgICAgICBbT1MgWF0gVXNlIENURm9udENyZWF0ZUZvckNTUyBpbnN0ZWFkIG9mIGRv aW5nIGZvbnQgc2VhcmNoIG91cnNlbHZlcwpJbmRleDogU291cmNlL1dURi93dGYvTmV2ZXJEZXN0 cm95ZWQuaAo9PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09Ci0tLSBTb3VyY2UvV1RGL3d0Zi9OZXZlckRlc3Ryb3llZC5oCShy ZXZpc2lvbiAxODM1MzQpCisrKyBTb3VyY2UvV1RGL3d0Zi9OZXZlckRlc3Ryb3llZC5oCSh3b3Jr aW5nIGNvcHkpCkBAIC0xMTYsNyArMTE2LDkgQEAgcHJpdmF0ZToKICAgICB9OwogCiAjaWYgIUFT U0VSVF9ESVNBQkxFRAotICAgIGJvb2wgbV9pc0NvbnN0cnVjdGVkID0gZmFsc2U7CisgICAgLy8g TGF6eU5ldmVyRGVzdHJveWVkIG9iamVjdHMgYXJlIGFsd2F5cyBzdGF0aWMsIHNvIHRoaXMgdmFy aWFibGUgaXMgaW5pdGlhbGl6ZWQgdG8gZmFsc2UuCisgICAgLy8gSXQgbXVzdCBub3QgYmUgaW5p dGlhbGl6ZWQgZHluYW1pY2FsbHksIGJlY2F1c2UgdGhhdCB3b3VsZCBub3QgYmUgdGhyZWFkIHNh ZmUuCisgICAgYm9vbCBtX2lzQ29uc3RydWN0ZWQ7CiAjZW5kaWYKIH07CiAK