Temporary destroyed before aggregate initialization completes

[71iq]

Version

Compiler: 7.0, commit 43e10b90fc83ed2a436fb79b241be8dbf3dc6846
Platform: Linux x86_64 (LP64)
Reference/compiler for generated C: GCC 13.3.0
Preset: linux-gcc-debug, with EDG_CPFE_USE_ASAN=OFF

Relevant configuration:

#define BACK_END_IS_C_GEN_BE 1
#define C_GEN_BE_GENERATES_ANSI_C 1
#define GNU_EXTENSIONS_ALLOWED 1
#define TARG_CHAR_BIT 8
#define TARG_SIZEOF_INT 4
#define TARG_SIZEOF_LONG 8
#define TARG_SIZEOF_POINTER 8

Code to reproduce

#include <cassert>

bool gone = false;
struct Temp { ~Temp() { gone = true; } };
struct A { A() {} A(const Temp&) noexcept {} };
struct Pair { A a; int b; };

int bar() { assert(!gone); return 1; }

int main()
{
    assert(!gone);
    Pair p{A(Temp{}), bar()};
    assert(gone);
    (void)p;
}

Compiler options:

--c++20 --no_exceptions --gnu_version=130300 --gen_c_file_name lifetime.cpp.int.c lifetime.cpp.ii

Behavior

The temporary Temp{}, bound to the constructor's reference parameter, should remain alive until the initialization of p completes. Both assertions should pass.

The reference program compiled with GCC exits with status 0. Compilation through the C-generating backend succeeds, but the translated program aborts inside bar():

Assertion `!gone' failed.

The generated C calls Temp::~Temp() before calling bar(), so gone is already true while initializing p.b.

C++20 [class.temporary]/4 and /6.9 require destruction at the end of the containing full-expression. Sequencing the aggregate's elements does not create a separate destruction boundary for each initializer.

References: class.temporary, intro.execution, dcl.init.aggr.

The same destructor placement occurs with exceptions enabled; --no_exceptions lets this small translated program link without the C++ support runtime.

The attachment contains the full --dump_configuration output and self-contained reproduction inputs.

Source, generated C, results, and full configuration

Reporting acknowledgements

I acknowledge that:

• I have checked open issues and existing discussions before filing this report.
• The reproducing source code that I have provided does not depend on headers that I have not included with my submission.
• I have reduced the reproducing source code to the best of my ability.
• I have selected at least one standard configuration or uploaded a non-standard configuration dump.
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• I have permission to share the reproducing source code and grant permission for the project to use the source code (or derivatives of the source code) to create tests.
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