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PR c++/86485 - -Wmaybe-unused with empty class ?:

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The problem in this testcase is that the front end expects an rvalue
COND_EXPR to initialize a single temporary from one of the arms.  But
because gimplify_cond_expr used MODIFY_EXPR, instead the arms would each
create their own temporary and then copy that into the common temporary.

So, let's use INIT_EXPR instead.

	* gimplify.c (gimplify_cond_expr): Use INIT_EXPR.

From-SVN: r269403
This commit is contained in:
Jason Merrill 2019-03-05 17:20:41 -05:00 committed by Jason Merrill
parent dbcd32f889
commit 507318f109
3 changed files with 19 additions and 2 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2019-03-02 Jason Merrill <jason@redhat.com>
PR c++/86485 - -Wmaybe-unused with empty class ?:
* gimplify.c (gimplify_cond_expr): Use INIT_EXPR.
2019-03-05 Jakub Jelinek <jakub@redhat.com>
PR target/89587

4
gcc/gimplify.c
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@ -4024,11 +4024,11 @@ gimplify_cond_expr (tree *expr_p, gimple_seq *pre_p, fallback_t fallback)
/* Build the new then clause, `tmp = then_;'. But don't build the
assignment if the value is void; in C++ it can be if it's a throw. */
if (!VOID_TYPE_P (TREE_TYPE (then_)))
TREE_OPERAND (expr, 1) = build2 (MODIFY_EXPR, type, tmp, then_);
TREE_OPERAND (expr, 1) = build2 (INIT_EXPR, type, tmp, then_);
/* Similarly, build the new else clause, `tmp = else_;'. */
if (!VOID_TYPE_P (TREE_TYPE (else_)))
TREE_OPERAND (expr, 2) = build2 (MODIFY_EXPR, type, tmp, else_);
TREE_OPERAND (expr, 2) = build2 (INIT_EXPR, type, tmp, else_);
TREE_TYPE (expr) = void_type_node;
recalculate_side_effects (expr);

12
gcc/testsuite/g++.dg/init/empty2.C Normal file
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@ -0,0 +1,12 @@
// PR c++/86485
// { dg-additional-options -Wmaybe-uninitialized }
struct E {};
struct S { S () {} E e; };
void foo (S);
void
bar (bool b)
{
foo (b ? S () : S ());
}