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Implement P0135R1, Guaranteed copy elision.

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* cvt.c (ocp_convert): Don't re-copy a TARGET_EXPR in C++17.

From-SVN: r240820
This commit is contained in:
Jason Merrill 2016-10-05 18:59:02 -04:00 committed by Jason Merrill
parent 5794b9f622
commit bf9b09fbe2
3 changed files with 24 additions and 2 deletions
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3
gcc/cp/ChangeLog
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@ -1,5 +1,8 @@
2016-10-05 Jason Merrill <jason@redhat.com>
Implement P0135R1, Guaranteed copy elision.
* cvt.c (ocp_convert): Don't re-copy a TARGET_EXPR in C++17.
PR c++/54293
* call.c (reference_binding): Fix binding to member of temporary.

7
gcc/cp/cvt.c
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@ -693,8 +693,11 @@ ocp_convert (tree type, tree expr, int convtype, int flags,
if (error_operand_p (e))
return error_mark_node;
if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP))
/* We need a new temporary; don't take this shortcut. */;
if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP)
&& !(cxx_dialect >= cxx1z
&& TREE_CODE (e) == TARGET_EXPR))
/* We need a new temporary; don't take this shortcut. But in C++17, don't
force a temporary if we already have one. */;
else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e)))
{
if (same_type_p (type, TREE_TYPE (e)))

16
gcc/testsuite/g++.dg/cpp1z/elide1.C Normal file
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@ -0,0 +1,16 @@
// { dg-options -std=c++1z }
struct A
{
A();
A(const A&) = delete;
};
bool b;
A a = A();
A a1 = b ? A() : A();
A a2 = (42, A());
A f();
A a3 = f();
A a4 = b ? A() : f();