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c++: constinit and value-initialization [PR119652]

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Value-initialization built an AGGR_INIT_EXPR to set AGGR_INIT_ZERO_FIRST on.
Passing that AGGR_INIT_EXPR to maybe_constant_value returned a TARGET_EXPR,
which potential_constant_expression_1 mistook for a temporary.

We shouldn't add a TARGET_EXPR to the AGGR_INIT_EXPR in this case, just like
we already avoid adding it to CONSTRUCTOR or CALL_EXPR.

	PR c++/119652

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_outermost_constant_expr): Also don't add a
	TARGET_EXPR around AGGR_INIT_EXPR.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/constinit20.C: New test.
This commit is contained in:
Jason Merrill 2025-04-07 11:49:19 -04:00
parent 3a77a567b1
commit c7dc9b6f88
2 changed files with 20 additions and 1 deletions
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3
gcc/cp/constexpr.cc
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@ -9316,7 +9316,8 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
if (TREE_CODE (t) == TARGET_EXPR
&& TARGET_EXPR_INITIAL (t) == r)
return t;
else if (TREE_CODE (t) == CONSTRUCTOR || TREE_CODE (t) == CALL_EXPR)
else if (TREE_CODE (t) == CONSTRUCTOR || TREE_CODE (t) == CALL_EXPR
|| TREE_CODE (t) == AGGR_INIT_EXPR)
/* Don't add a TARGET_EXPR if our argument didn't have one. */;
else if (TREE_CODE (t) == TARGET_EXPR && TARGET_EXPR_CLEANUP (t))
r = get_target_expr (r);

18
gcc/testsuite/g++.dg/cpp2a/constinit20.C Normal file
View file

@ -0,0 +1,18 @@
// PR c++/119652
// { dg-do compile { target c++20 } }
struct __shared_count {
constexpr __shared_count() {}
~__shared_count();
int _M_pi = 0;
};
struct shared_ptr {
__shared_count _M_refcount;
};
struct A {
A() = default;
shared_ptr m;
};
constinit A a;
constinit A b {};
constinit A c = {};