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c++: Fix paren init of aggregates in unevaluated context [PR92947]

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When I implemented C++20 parenthesized initialization of aggregates
I introduced this bogus cp_unevaluated_operand check, thus disabling
this feature in unevaluated context.  Oop.

Removing the check turned up another bug: I wasn't checking the
return value of digest_init.  So when constructible_expr called
build_new_method_call_1 to see if we can construct one type from
another, it got back a bogus INIT_EXPR that looked something like
*(struct T &) 1 = <<< error >>>.  But that isn't the error_mark_node,
so constructible_expr thought we had been successful in creating the
ctor call, and it gave the wrong answer.  Covered by paren-init17.C.

	PR c++/92947 - Paren init of aggregates in unevaluated context.
	* call.c (build_new_method_call_1): Don't check
	cp_unevaluated_operand.  Check the return value of digest_init.

	* g++.dg/cpp2a/paren-init21.C: New test.
This commit is contained in:
Marek Polacek 2020-02-07 14:44:25 -05:00
parent 8496e135b1
commit ac6eaa55a5
4 changed files with 27 additions and 1 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2020-02-07 Marek Polacek <polacek@redhat.com>
PR c++/92947 - Paren init of aggregates in unevaluated context.
* call.c (build_new_method_call_1): Don't check
cp_unevaluated_operand. Check the return value of digest_init.
2020-02-06 Jason Merrill <jason@redhat.com>
PR c++/92654

3
gcc/cp/call.c
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@ -10179,7 +10179,6 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
the two. */
if (DECL_CONSTRUCTOR_P (fn)
&& !(flags & LOOKUP_ONLYCONVERTING)
&& !cp_unevaluated_operand
&& cxx_dialect >= cxx2a
&& CP_AGGREGATE_TYPE_P (basetype)
&& !user_args->is_empty ())
@ -10194,6 +10193,8 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
else
{
ctor = digest_init (basetype, ctor, complain);
if (ctor == error_mark_node)
return error_mark_node;
ctor = build2 (INIT_EXPR, TREE_TYPE (instance), instance, ctor);
TREE_SIDE_EFFECTS (ctor) = true;
return ctor;

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2020-02-07 Marek Polacek <polacek@redhat.com>
PR c++/92947 - Paren init of aggregates in unevaluated context.
* g++.dg/cpp2a/paren-init21.C: New test.
2020-02-07 Will Schmidt <will_schmidt@vnet.ibm.com>
* testsuite/gcc.target/powerpc/pr92923-1.c: Add -mvsx.

14
gcc/testsuite/g++.dg/cpp2a/paren-init21.C Normal file
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@ -0,0 +1,14 @@
// PR c++/92947 - Paren init of aggregates in unevaluated context.
// { dg-do compile { target c++2a } }
struct A {
int a;
int b;
};
int main()
{
static_assert(__is_constructible(A, int, int));
decltype(A(1,2)) foo;
bool b = noexcept(A(1,2));
}