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c++: Tweak PR969626 patch

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It occurred to me that other types of conversions use rvaluedness_matches_p,
but those uses don't affect overload resolution, so we shouldn't look at the
flag for them.  Fixing that made decltype64.C compile successfully, because
the non-template candidate was a perfect match, so we now wouldn't consider
the broken template.  Changing the argument to const& makes it no longer a
perfect match (because of the added const), so we again get the infinite
recursion.

This illustrates the limited nature of this optimization/recursion break; it
works for most copy/move constructors because the constructor we're looking
for is almost always a perfect match.  If it happens to help improve compile
time for other calls, that's just a bonus.

gcc/cp/ChangeLog:

	PR c++/96926
	* call.c (perfect_conversion_p): Limit rvalueness
	test to reference bindings.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/decltype64.C: Change argument to const&.
This commit is contained in:
Jason Merrill 2021-02-18 21:27:37 -05:00
parent b258e263e0
commit d909ead682
2 changed files with 9 additions and 7 deletions
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14
gcc/cp/call.c
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@ -5864,12 +5864,14 @@ perfect_conversion_p (conversion *conv)
{
if (CONVERSION_RANK (conv) != cr_identity)
return false;
if (!conv->rvaluedness_matches_p)
return false;
if (conv->kind == ck_ref_bind
&& !same_type_p (TREE_TYPE (conv->type),
next_conversion (conv)->type))
return false;
if (conv->kind == ck_ref_bind)
{
if (!conv->rvaluedness_matches_p)
return false;
if (!same_type_p (TREE_TYPE (conv->type),
next_conversion (conv)->type))
return false;
}
return true;
}

2
gcc/testsuite/g++.dg/cpp0x/decltype64.C
View file

@ -5,7 +5,7 @@ template<int I>
struct index
{};
constexpr int recursive_impl(index<0u>)
constexpr int recursive_impl(const index<0u>&)
{
return 0;
}