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[Sema] Fix lifetime extension for temporaries in range-based for loops in C++23 #145164

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Merged
merged 5 commits into from
Jul 10, 2025
Merged

[Sema] Fix lifetime extension for temporaries in range-based for loops in C++23 #145164

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37c5713
[Sema] Fix lifetime extension for temporaries in range-based for loop…
mrcvtl Jun 21, 2025
d9a88d5
Address feedbacks
mrcvtl Jun 28, 2025
b40d507
Move check to support clang::lifetimebound and boost performance
mrcvtl Jul 1, 2025
71ba6f0
Move check in the switch case
mrcvtl Jul 6, 2025
a045c67
Merge branch 'main' into main
mrcvtl Jul 9, 2025
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15 changes: 7 additions & 8 deletions clang/lib/Sema/CheckExprLifetime.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1304,6 +1304,13 @@ checkExprLifetimeImpl(Sema &SemaRef, const InitializedEntity *InitEntity,
if (LK == LK_FullExpression)
return;

if (LK == LK_Extended && SemaRef.getLangOpts().CPlusPlus23) {
if (const auto *VD = dyn_cast_if_present<VarDecl>(InitEntity->getDecl())) {
if (VD->isCXXForRangeImplicitVar())
return;
}
}

// FIXME: consider moving the TemporaryVisitor and visitLocalsRetained*
// functions to a dedicated class.
auto TemporaryVisitor = [&](const IndirectLocalPath &Path, Local L,
Expand Down Expand Up @@ -1341,14 +1348,6 @@ checkExprLifetimeImpl(Sema &SemaRef, const InitializedEntity *InitEntity,
}

if (IsGslPtrValueFromGslTempOwner && DiagLoc.isValid()) {

if (SemaRef.getLangOpts().CPlusPlus23) {
if (const VarDecl *VD =
dyn_cast_if_present<VarDecl>(InitEntity->getDecl());
VD && VD->isCXXForRangeImplicitVar())
return false;
}

SemaRef.Diag(DiagLoc, diag::warn_dangling_lifetime_pointer)
<< DiagRange;
return false;
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5 changes: 3 additions & 2 deletions clang/test/SemaCXX/attr-lifetimebound.cpp
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Expand Up @@ -192,8 +192,9 @@ namespace p0936r0_examples {

std::vector make_vector();
void use_reversed_range() {
// FIXME: Don't expose the name of the internal range variable.
for (auto x : reversed(make_vector())) {} // expected-warning {{temporary implicitly bound to local reference will be destroyed at the end of the full-expression}}
// No warning here because C++23 extends the lifetime of the temporary
// in a range-based for loop.
for (auto x : reversed(make_vector())) {}
}

template <typename K, typename V>
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