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re PR c++/63924 (Constexpr constructible expression "is not constexpr" when used in a template non-type argument)

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PR c++/63924
	* constexpr.c (cxx_eval_constant_expression) [PARM_DECL]: A load
	from a variable of empty class type is constant.

From-SVN: r217749
This commit is contained in:
Jason Merrill 2014-11-18 22:03:45 -05:00 committed by Jason Merrill
parent 58611fb6fa
commit 052beba43f
3 changed files with 17 additions and 0 deletions
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4
gcc/cp/ChangeLog
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@ -1,5 +1,9 @@
2014-11-18 Jason Merrill <jason@redhat.com>
PR c++/63924
* constexpr.c (cxx_eval_constant_expression) [PARM_DECL]: A load
from a variable of empty class type is constant.
* constexpr.c (cxx_eval_statement_list): Handle statement-expressions.
(potential_constant_expression_1): Handle STMT_EXPR.

6
gcc/cp/constexpr.c
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@ -2845,6 +2845,12 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
r = *p;
else if (addr)
/* Defer in case this is only used for its type. */;
else if (is_empty_class (TREE_TYPE (t)))
{
/* If the class is empty, we aren't actually loading anything. */
r = build_constructor (TREE_TYPE (t), NULL);
TREE_CONSTANT (r) = true;
}
else
{
if (!ctx->quiet)

7
gcc/testsuite/g++.dg/cpp0x/constexpr-empty8.C Normal file
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@ -0,0 +1,7 @@
// PR c++/63924
// { dg-do compile { target c++11 } }
struct A { };
constexpr bool f(A a) { return true; }
template <bool B> constexpr bool g() { return true; }
constexpr bool g(A a) { return g<f(a)>(); }