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[clang] Compound Literal Statement Constant Expression Assertion Fix #139479

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[clang] Compound Literal Statement Constant Expression Assertion Fix #139479

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[clang] Compound Literal Statement Constant Expression Assertion Fix
Mr-Anyone May 11, 2025
b969ec1
Added Release Notes and moved comments and minor nits.
Mr-Anyone May 12, 2025
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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -589,6 +589,7 @@ Bug Fixes in This Version
- Fixed a crash with an invalid member function parameter list with a default
argument which contains a pragma. (#GH113722)
- Fixed assertion failures when generating name lookup table in modules. (#GH61065, #GH134739)
- Fixed an assertion failure in constant compound literal statements. (#GH139160)

Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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11 changes: 11 additions & 0 deletions clang/lib/Sema/SemaExpr.cpp
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Expand Up @@ -7241,10 +7241,21 @@ Sema::BuildCompoundLiteralExpr(SourceLocation LParenLoc, TypeSourceInfo *TInfo,
? VK_PRValue
: VK_LValue;

// C99 6.5.2.5
// "If the compound literal occurs outside the body of a function, the
// initializer list shall consist of constant expressions."
if (IsFileScope)
if (auto ILE = dyn_cast<InitListExpr>(LiteralExpr))
for (unsigned i = 0, j = ILE->getNumInits(); i != j; i++) {
Expr *Init = ILE->getInit(i);
if (!Init->isTypeDependent() && !Init->isValueDependent() &&
!Init->getType()->isDependentType())
Comment on lines +7251 to +7252
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This is not checking for "outside of the function".
Note that GCC errors on these cases too https://compiler-explorer.com/z/TaqzEdnbe
I think you need to update the comment to better describe the check

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There is a if (IsFileScope) 4 lines above.

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I have moved the comment to the if (IsFileScope), is that alright?

if (!Init->isConstantInitializer(Context, /*IsForRef=*/false)) {
Diag(Init->getExprLoc(), diag::err_init_element_not_constant)
<< Init->getSourceBitField();
return ExprError();
}

ILE->setInit(i, ConstantExpr::Create(Context, Init));
}

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22 changes: 22 additions & 0 deletions clang/test/SemaCXX/cxx2a-consteval.cpp
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Expand Up @@ -1300,3 +1300,25 @@ void foo() {
}

}

// https://github.com/llvm/llvm-project/issues/139160
namespace GH139160{
// original test case taken from Github
struct A {int x[1]; };
A f(); // expected-note {{declared here}}
typedef int *t[];
consteval int* f(int* x) { return x; }

int ** x = (t){f(f().x)}; // expected-error {{call to consteval function 'GH139160::f' is not a constant expression}}
// expected-note@-1 {{non-constexpr function 'f' cannot be used in a constant expression}}
// expected-error@-2 {{initializer element is not a compile-time constant}}

struct B {int value, value_two;};
B make_struct() {return {10, 20};} // expected-note {{declared here}}
consteval int get_value(B container) {return container.value;}
B result = (B){10, get_value(make_struct())}; // expected-error {{initializer element is not a compile-time constant}}
// expected-error@-1 {{call to consteval function 'GH139160::get_value' is not a constant expression}}
// expected-note@-2 {{non-constexpr function 'make_struct' cannot be used in a constant expression}}
};