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PR c++/86521 - wrong overload resolution with ref-qualifiers.

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Here we were wrongly treating binding a const lvalue ref to an xvalue as
direct binding, which is wrong under [dcl.init.ref] and [over.match.ref].

	* call.c (build_user_type_conversion_1): Don't use a conversion to a
	reference of the wrong rvalueness for direct binding.

From-SVN: r269602
This commit is contained in:
Jason Merrill 2019-03-11 23:19:22 -04:00 • committed by Jason Merrill
parent 6d5d5cb5b2
commit c7e936dbc7
4 changed files with 39 additions and 2 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2019-03-11 Jason Merrill <jason@redhat.com>
PR c++/86521 - wrong overload resolution with ref-qualifiers.
* call.c (build_user_type_conversion_1): Don't use a conversion to a
reference of the wrong rvalueness for direct binding.
2019-03-11 Martin Liska <mliska@suse.cz>
* cvt.c (build_expr_type_conversion): Wrap apostrophes

8
gcc/cp/call.c
View file

@ -4039,6 +4039,14 @@ build_user_type_conversion_1 (tree totype, tree expr, int flags,
rettype, totype,
EXPR_LOCATION (expr));
}
else if (TYPE_REF_P (totype) && !ics->rvaluedness_matches_p
&& TREE_CODE (TREE_TYPE (totype)) != FUNCTION_TYPE)
{
/* If we are called to convert to a reference type, we are trying
to find a direct binding per [over.match.ref], so rvaluedness
must match for non-functions. */
cand->viable = 0;
}
else if (DECL_NONCONVERTING_P (cand->fn)
&& ics->rank > cr_exact)
{

21
gcc/testsuite/g++.dg/cpp0x/overload-conv-3.C Normal file
View file

@ -0,0 +1,21 @@
// PR c++/86521
// { dg-do compile { target c++11 } }
template <class T> T&& move (T&);
struct Dest {
Dest() = default;
Dest( Dest && ) = default;
Dest( Dest const & ) = delete;
};
struct Source {
Dest val;
operator Dest () && { return move( val ); }
operator Dest const & () const & { return val; }
};
int main() {
Source x;
Dest d(move(x)); // { dg-error "ambiguous" }
}

6
libstdc++-v3/testsuite/20_util/is_constructible/value-2.cc
View file

@ -806,10 +806,12 @@ static_assert(!std::is_constructible<int&&, ExplicitTo<int>>::value, "Error");
// Binding through reference-compatible type is required to perform
// direct-initialization as described in [over.match.ref] p. 1 b. 1:
static_assert(std::is_constructible<int&, ExplicitTo<int&>>::value, "Error");
static_assert(std::is_constructible<const int&, ExplicitTo<int&&>>::value,
"Error");
static_assert(std::is_constructible<int&&, ExplicitTo<int&&>>::value, "Error");
// But an xvalue doesn't count for direct binding.
static_assert(!std::is_constructible<const int&, ExplicitTo<int&&>>::value,
"Error");
// Binding through temporary behaves like copy-initialization,
// see [dcl.init.ref] p. 5, very last sub-bullet:
static_assert(!std::is_constructible<const int&, ExplicitTo<double&&>>::value,