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c++: __is_trivially_xible and multi-arg aggr paren init [PR102535]

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is_xible_helper assumes only 0- and 1-argument ctors can be trivial, but
C++20 aggregate paren init means multi-arg ctors can now be trivial too.
This patch relaxes the relevant early exit check accordingly.

	PR c++/102535

gcc/cp/ChangeLog:

	* method.c (is_xible_helper): Don't exit early for multi-arg
	ctors in C++20.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/is_trivially_constructible7.C: New test.
This commit is contained in:
Patrick Palka 2021-09-30 17:34:23 -04:00
parent fdf8d5bc5b
commit 9845c52db3
2 changed files with 20 additions and 1 deletions
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4
gcc/cp/method.c
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@ -2094,8 +2094,10 @@ is_xible_helper (enum tree_code code, tree to, tree from, bool trivial)
tree expr;
if (code == MODIFY_EXPR)
expr = assignable_expr (to, from);
else if (trivial && from && TREE_CHAIN (from))
else if (trivial && from && TREE_CHAIN (from)
&& cxx_dialect < cxx20)
return error_mark_node; // only 0- and 1-argument ctors can be trivial
// before C++20 aggregate paren init
else if (TREE_CODE (to) == ARRAY_TYPE && !TYPE_DOMAIN (to))
return error_mark_node; // can't construct an array of unknown bound
else

17
gcc/testsuite/g++.dg/ext/is_trivially_constructible7.C Normal file
View File

@ -0,0 +1,17 @@
// PR c++/102535
// Verify __is_trivially_constructible works with multi-arg paren init of
// aggrs.
struct A { int x; };
struct B { float y; };
struct C { char z; };
struct D { A a; B b; C c; };
extern int n[1 + __is_trivially_constructible(D, A)];
extern int n[1 + __is_trivially_constructible(D, A, B)];
extern int n[1 + __is_trivially_constructible(D, A, B, C)];
#if __cpp_aggregate_paren_init
extern int n[1 + true];
#else
extern int n[1 + false];
#endif