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[clang] Fix crash on invalid std::initializer_list<T> template-id #132284

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Merged
merged 3 commits into from
Apr 1, 2025
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[clang] Fix crash on invalid std::initializer_list<T> template-id #132284

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[clang] Fix crash on invalid `std::initializer_list<T>` template-id
offsetof Mar 20, 2025
bd5c32e
fixup! [clang] Fix crash on invalid `std::initializer_list<T>` templa…
offsetof Mar 24, 2025
a501965
Merge branch 'main' into issue132256
offsetof Mar 31, 2025
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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -357,6 +357,7 @@ Bug Fixes to C++ Support
- Fixed a Clang regression in C++20 mode where unresolved dependent call expressions were created inside non-dependent contexts (#GH122892)
- Clang now emits the ``-Wunused-variable`` warning when some structured bindings are unused
and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
- Fixed a crash caused by invalid declarations of ``std::initializer_list``. (#GH132256)

Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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8 changes: 6 additions & 2 deletions clang/lib/Sema/SemaDeclCXX.cpp
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Expand Up @@ -12182,10 +12182,14 @@ QualType Sema::BuildStdInitializerList(QualType Element, SourceLocation Loc) {
Args.addArgument(TemplateArgumentLoc(TemplateArgument(Element),
Context.getTrivialTypeSourceInfo(Element,
Loc)));

QualType T = CheckTemplateIdType(TemplateName(StdInitializerList), Loc, Args);
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@ojhunt ojhunt Mar 25, 2025

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We should probably keep this as an additional sanity check, however I think in this particular case the error is in the validity check in LookupStdInitializerList, where it is checking the minimum required template parameters, rather than ensuring real correctness.

It should probably be doing Params->size() != 1, and ensuring that there isn't a parameter pack or any default template arguments.

Changing those validity checks will also result in a much more direct error saying std::initializer_list is defined incorrectly.

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@offsetof offsetof Mar 31, 2025

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I opened a separate PR for this change: #133822

if (T.isNull())
return QualType();

return Context.getElaboratedType(
ElaboratedTypeKeyword::None,
NestedNameSpecifier::Create(Context, nullptr, getStdNamespace()),
CheckTemplateIdType(TemplateName(StdInitializerList), Loc, Args));
NestedNameSpecifier::Create(Context, nullptr, getStdNamespace()), T);
}

bool Sema::isInitListConstructor(const FunctionDecl *Ctor) {
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18 changes: 18 additions & 0 deletions clang/test/SemaCXX/invalid-std-initializer-list.cpp
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@@ -0,0 +1,18 @@
// RUN: %clang_cc1 %s -verify -std=c++20

namespace std {

template<class T, class = T::x> // expected-error 2 {{type 'int' cannot be used prior to '::' because it has no members}}
class initializer_list;

}

namespace gh132256 {

auto x = {1}; // expected-note {{in instantiation of default argument for 'initializer_list<int>' required here}}

void f() {
for(int x : {1, 2}); // expected-note {{in instantiation of default argument for 'initializer_list<int>' required here}}
}
Comment on lines +11 to +16
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@zyn0217 zyn0217 Mar 21, 2025

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We usually wrap the test with a namespace of its corresponding GH number.

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@offsetof offsetof Mar 24, 2025

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Added a namespace and a release note.


}