239299 2022-04-13 13:06:52 -0700 GCC 12 -Wdangling-pointer warning spam from AbstractSlotVisitorInlines.h 2022-04-14 09:46:44 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build PC Linux RESOLVED FIXED InRadar P2 Normal --- 1 mcatanzaro mcatanzaro ews-watchlist keith_miller mark.lam mcatanzaro msaboff saam tzagallo webkit-bug-importer zan oldest_to_newest 1861233 0 mcatanzaro 2022-04-13 13:06:52 -0700 GCC 12 has added a -Wdangling-pointer warning, which surprisingly WebKit survives quite well. It only trips once in JavaScriptCore at AbstractSlotVisitorInlines.h:77. Sadly, that's a header file, so it creates a huge warning spam as the warning gets printed again for every translation unit that includes AbstractSlotVisitorInlines.h. The full warning is: In file included from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/SlotVisitorInlines.h:28, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSCellInlines.h:45, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSCJSValueInlines.h:35, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/StructureInlines.h:30, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/ArrayStorageInlines.h:29, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/ButterflyInlines.h:28, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSObjectInlines.h:28, from /home/mcatanzaro/Projects/WebKit/Source/WebCore/bindings/js/JSDOMGlobalObject.h:32, from /home/mcatanzaro/Projects/WebKit/Source/WebCore/bindings/js/JSDOMWrapper.h:24, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/WebCore/DerivedSources/JSDeprecatedCSSOMRect.h:24, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/WebCore/DerivedSources/JSDeprecatedCSSOMRect.cpp:22, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/WebCore/DerivedSources/unified-sources/UnifiedSource-3a52ce78-34.cpp:1: In constructor ‘JSC::AbstractSlotVisitor::ReferrerContext::ReferrerContext(JSC::AbstractSlotVisitor&, JSC::AbstractSlotVisitor::ReferrerToken)’, inlined from ‘static void JSC::JSCell::visitOutputConstraints(JSC::JSCell*, JSC::AbstractSlotVisitor&)’ at /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSCellInlines.h:158:1: /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/AbstractSlotVisitorInlines.h:77:25: warning: storing the address of local variable ‘context’ in ‘*visitor.JSC::AbstractSlotVisitor::m_context’ [-Wdangling-pointer=] 77 | m_visitor.m_context = this; | ~~~~~~~~~~~~~~~~~~~~^~~~~~ In file included from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSCell.h:35, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSArray.h:26, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/ArrayAllocationProfile.h:29, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSGlobalObject.h:24, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/InternalFunctionAllocationProfile.h:28, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/FunctionRareData.h:28, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSFunction.h:26, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/WebCore/DerivedSources/JSDOMBindingInternalsBuiltins.h:35, from /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/WebCore/DerivedSources/WebCoreJSBuiltinInternals.h:38, from /home/mcatanzaro/Projects/WebKit/Source/WebCore/bindings/js/JSDOMGlobalObject.h:29: /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/JSCellInlines.h: In static member function ‘static void JSC::JSCell::visitOutputConstraints(JSC::JSCell*, JSC::AbstractSlotVisitor&)’: /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/SlotVisitorMacros.h:104:46: note: ‘context’ declared here 104 | AbstractSlotVisitor::ReferrerContext context(visitor, cell); \ | ^~~~~~~ /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/SlotVisitorMacros.h:104:46: note: in definition of macro ‘DEFINE_VISIT_OUTPUT_CONSTRAINTS_WITH_MODIFIER’ 104 | AbstractSlotVisitor::ReferrerContext context(visitor, cell); \ | ^~~~~~~ /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/SlotVisitorMacros.h:104:46: note: ‘visitor’ declared here 104 | AbstractSlotVisitor::ReferrerContext context(visitor, cell); \ | ^~~~~~~ /home/mcatanzaro/Projects/WebKit/WebKitBuild/GNOME-gtk3/JavaScriptCore/PrivateHeaders/JavaScriptCore/SlotVisitorMacros.h:104:46: note: in definition of macro ‘DEFINE_VISIT_OUTPUT_CONSTRAINTS_WITH_MODIFIER’ 104 | AbstractSlotVisitor::ReferrerContext context(visitor, cell); \ | ^~~~~~~ I'll attach a patch to suppress the warning -- since it makes it difficult to see any other warnings -- but review from JSC devs would be appreciated, because frankly I have no clue whether this is a disaster or (more likely?) just a false positive. I guess the purported dangling pointer is the AbstractSlotVisitor::ReferrerContext declared in DEFINE_VISIT_OUTPUT_CONSTRAINTS_WITH_MODIFIER and used in JSCellInlines.h, but I don't see where it gets stored as part of the AbstractSlotVisitor::ReferrerContext object and certainly don't understand why that would be done. 1861236 1 457563 mcatanzaro 2022-04-13 13:08:17 -0700 Created attachment 457563 Patch 1861260 2 457563 mark.lam 2022-04-13 14:37:45 -0700 Comment on attachment 457563 Patch r=me 1861291 3 mcatanzaro 2022-04-13 15:41:09 -0700 (In reply to Mark Lam from comment #2) > r=me OK, I'll take that to mean you've determined the warning is a false positive. I'm not too surprised. 1861299 4 mark.lam 2022-04-13 15:52:46 -0700 (In reply to Michael Catanzaro from comment #3) > (In reply to Mark Lam from comment #2) > > r=me > > OK, I'll take that to mean you've determined the warning is a false > positive. I'm not too surprised. Yes, it's set and used while the AbstractSlotVisitor::ReferrerContext is on stack, and cleared out on destruction: inline AbstractSlotVisitor::ReferrerContext::ReferrerContext(AbstractSlotVisitor& visitor, ReferrerToken referrer) : m_visitor(visitor) , m_referrer(referrer) { m_previous = m_visitor.m_context; ... m_visitor.m_context = this; } inline AbstractSlotVisitor::ReferrerContext::~ReferrerContext() { m_visitor.m_context = m_previous; } The warning is wrong. 1861313 5 ews-feeder 2022-04-13 16:15:19 -0700 Committed r292841 (249614@main): <https://commits.webkit.org/249614@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 457563. 1861315 6 webkit-bug-importer 2022-04-13 16:16:20 -0700 <rdar://problem/91721538> 1861409 7 zan 2022-04-13 23:38:45 -0700 Now every supported GCC version below 12 is complaining: [1897/2120] Building CXX object Source/WebKit/CMakeFiles/WebKit.dir/WebProcess/WebPage/WebPage.cpp.o In file included from /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Platform.h:31, from /work/webkit/git/Source/WebKit/WebKit2Prefix.h:31, from <command-line>: /build/webkit/build-unstable/build-webkit/JavaScriptCore/PrivateHeaders/JavaScriptCore/AbstractSlotVisitorInlines.h: In constructor ‘JSC::AbstractSlotVisitor::ReferrerContext::ReferrerContext(JSC::AbstractSlotVisitor&, JSC::AbstractSlotVisitor::ReferrerToken)’: /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:451:5: warning: unknown option after ‘#pragma GCC diagnostic’ kind [-Wpragmas] 451 | _Pragma(_COMPILER_STRINGIZE(compiler diagnostic ignored warning)) | ^~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:438:34: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_IMPL_1’ 438 | #define _COMPILER_CONCAT_I(a, b) a ## b | ^ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:439:32: note: in expansion of macro ‘_COMPILER_CONCAT_I’ 439 | #define _COMPILER_CONCAT(a, b) _COMPILER_CONCAT_I(a, b) | ^~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:448:5: note: in expansion of macro ‘_COMPILER_CONCAT’ 448 | _COMPILER_CONCAT(IGNORE_WARNINGS_BEGIN_IMPL_, cond)(compiler, warning) | ^~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:462:56: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_COND’ 462 | #define _IGNORE_WARNINGS_BEGIN_IMPL(compiler, warning) IGNORE_WARNINGS_BEGIN_COND(1, compiler, warning) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:466:5: note: in expansion of macro ‘_IGNORE_WARNINGS_BEGIN_IMPL’ 466 | _IGNORE_WARNINGS_BEGIN_IMPL(compiler, _COMPILER_WARNING_NAME(warning)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:472:44: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_IMPL’ 472 | #define IGNORE_GCC_WARNINGS_BEGIN(warning) IGNORE_WARNINGS_BEGIN_IMPL(GCC, warning) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/JavaScriptCore/PrivateHeaders/JavaScriptCore/AbstractSlotVisitorInlines.h:77:1: note: in expansion of macro ‘IGNORE_GCC_WARNINGS_BEGIN’ 77 | IGNORE_GCC_WARNINGS_BEGIN("dangling-pointer") | ^~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:451:5: note: did you mean ‘-Wdangling-else’? 451 | _Pragma(_COMPILER_STRINGIZE(compiler diagnostic ignored warning)) | ^~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:438:34: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_IMPL_1’ 438 | #define _COMPILER_CONCAT_I(a, b) a ## b | ^ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:439:32: note: in expansion of macro ‘_COMPILER_CONCAT_I’ 439 | #define _COMPILER_CONCAT(a, b) _COMPILER_CONCAT_I(a, b) | ^~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:448:5: note: in expansion of macro ‘_COMPILER_CONCAT’ 448 | _COMPILER_CONCAT(IGNORE_WARNINGS_BEGIN_IMPL_, cond)(compiler, warning) | ^~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:462:56: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_COND’ 462 | #define _IGNORE_WARNINGS_BEGIN_IMPL(compiler, warning) IGNORE_WARNINGS_BEGIN_COND(1, compiler, warning) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:466:5: note: in expansion of macro ‘_IGNORE_WARNINGS_BEGIN_IMPL’ 466 | _IGNORE_WARNINGS_BEGIN_IMPL(compiler, _COMPILER_WARNING_NAME(warning)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/WTF/Headers/wtf/Compiler.h:472:44: note: in expansion of macro ‘IGNORE_WARNINGS_BEGIN_IMPL’ 472 | #define IGNORE_GCC_WARNINGS_BEGIN(warning) IGNORE_WARNINGS_BEGIN_IMPL(GCC, warning) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ /build/webkit/build-unstable/build-webkit/JavaScriptCore/PrivateHeaders/JavaScriptCore/AbstractSlotVisitorInlines.h:77:1: note: in expansion of macro ‘IGNORE_GCC_WARNINGS_BEGIN’ 77 | IGNORE_GCC_WARNINGS_BEGIN("dangling-pointer") | ^~~~~~~~~~~~~~~~~~~~~~~~~ 1861475 8 mcatanzaro 2022-04-14 07:12:10 -0700 Well that is frustrating. I might have to test compiler version manually here. 1861543 9 mcatanzaro 2022-04-14 09:46:44 -0700 (In reply to Michael Catanzaro from comment #8) > Well that is frustrating. I might have to test compiler version manually > here. I found another way... let's use bug #239344 457563 2022-04-13 13:08:17 -0700 2022-04-13 16:15:21 -0700 Patch bug-239299-20220413150816.patch text/plain 1665 mcatanzaro U3VidmVyc2lvbiBSZXZpc2lvbjogMjkyODE5CmRpZmYgLS1naXQgYS9Tb3VyY2UvSmF2YVNjcmlw dENvcmUvQ2hhbmdlTG9nIGIvU291cmNlL0phdmFTY3JpcHRDb3JlL0NoYW5nZUxvZwppbmRleCBl Yjk0M2U2M2UxYzM4MjRjMjdlNmU2ZjE2Mjk2MjI5ZDNmNzY1MTZhLi41NzlmNzYzZGIwZDZmYjA5 NzJhZWFkZDc5Y2FhMDJlZWFjNGI3YTAyIDEwMDY0NAotLS0gYS9Tb3VyY2UvSmF2YVNjcmlwdENv cmUvQ2hhbmdlTG9nCisrKyBiL1NvdXJjZS9KYXZhU2NyaXB0Q29yZS9DaGFuZ2VMb2cKQEAgLTEs MyArMSwxNSBAQAorMjAyMi0wNC0xMyAgTWljaGFlbCBDYXRhbnphcm8gIDxtY2F0YW56YXJvQHJl ZGhhdC5jb20+CisKKyAgICAgICAgR0NDIDEyIC1XZGFuZ2xpbmctcG9pbnRlciB3YXJuaW5nIHNw YW0gZnJvbSBBYnN0cmFjdFNsb3RWaXNpdG9ySW5saW5lcy5oCisgICAgICAgIGh0dHBzOi8vYnVn cy53ZWJraXQub3JnL3Nob3dfYnVnLmNnaT9pZD0yMzkyOTkKKworICAgICAgICBSZXZpZXdlZCBi eSBOT0JPRFkgKE9PUFMhKS4KKyAgICAgICAgCisgICAgICAgIFN1cHByZXNzIHRoaXMgd2Fybmlu Zywgc28gd2UgY2FuIHNlZSBvdGhlciB3YXJuaW5ncy4KKworICAgICAgICAqIGhlYXAvQWJzdHJh Y3RTbG90VmlzaXRvcklubGluZXMuaDoKKyAgICAgICAgKEpTQzo6QWJzdHJhY3RTbG90VmlzaXRv cjo6UmVmZXJyZXJDb250ZXh0OjpSZWZlcnJlckNvbnRleHQpOgorCiAyMDIyLTA0LTEzICBDaHJp cyBEdW1leiAgPGNkdW1lekBhcHBsZS5jb20+CiAKICAgICAgICAgUmVwbGFjZSBBdG9tU3RyaW5n KGNvbnN0IGNoYXIqKSB3aXRoIEF0b21TdHJpbmc6OmZyb21MYXRpbjEoY29uc3QgY2hhciopCmRp ZmYgLS1naXQgYS9Tb3VyY2UvSmF2YVNjcmlwdENvcmUvaGVhcC9BYnN0cmFjdFNsb3RWaXNpdG9y SW5saW5lcy5oIGIvU291cmNlL0phdmFTY3JpcHRDb3JlL2hlYXAvQWJzdHJhY3RTbG90VmlzaXRv cklubGluZXMuaAppbmRleCA2Mjg0MzgyZTAwMjExNTY5OGU1Mjk1NmIyZDMxYmRmODE2NmQyYzZh Li5jYzgzNzZlN2Y2NDYzNmY3MjY1MDdkYjIzYzg3ZDU3NWM2NjA5NTliIDEwMDY0NAotLS0gYS9T b3VyY2UvSmF2YVNjcmlwdENvcmUvaGVhcC9BYnN0cmFjdFNsb3RWaXNpdG9ySW5saW5lcy5oCisr KyBiL1NvdXJjZS9KYXZhU2NyaXB0Q29yZS9oZWFwL0Fic3RyYWN0U2xvdFZpc2l0b3JJbmxpbmVz LmgKQEAgLTc0LDcgKzc0LDkgQEAgaW5saW5lIEFic3RyYWN0U2xvdFZpc2l0b3I6OlJlZmVycmVy Q29udGV4dDo6UmVmZXJyZXJDb250ZXh0KEFic3RyYWN0U2xvdFZpc2l0b3IKICAgICAgICAgLy8g QW4gT3BhcXVlUm9vdCBjb250ZXh0cyBjYW4gb25seSBiZSBvbiB0aGUgbGVhZi4KICAgICAgICAg UkVMRUFTRV9BU1NFUlQoIW1fcHJldmlvdXMtPm1faXNPcGFxdWVSb290Q29udGV4dCk7CiAgICAg fQorSUdOT1JFX0dDQ19XQVJOSU5HU19CRUdJTigiZGFuZ2xpbmctcG9pbnRlciIpCiAgICAgbV92 aXNpdG9yLm1fY29udGV4dCA9IHRoaXM7CitJR05PUkVfR0NDX1dBUk5JTkdTX0VORAogfQogCiBp bmxpbmUgQWJzdHJhY3RTbG90VmlzaXRvcjo6UmVmZXJyZXJDb250ZXh0OjpSZWZlcnJlckNvbnRl eHQoQWJzdHJhY3RTbG90VmlzaXRvciYgdmlzaXRvciwgQWJzdHJhY3RTbG90VmlzaXRvcjo6T3Bh cXVlUm9vdFRhZykK