On Wed, 22 Mar 2017, Jakub Jelinek wrote:
> On Wed, Mar 22, 2017 at 09:59:09AM +0100, Richard Biener wrote:
> > Yeah, changing it to VAR_P and expanding the comment so it says
> > it avoids incorrect promotion to readonly-static. (so it _is_
> > fishy that we have multiple assignments to TREE_READONLY objects
> > given that code looks at a single assignment only)
>
> So like this?
Yes.
Thanks,
Richard.
> 2017-03-22 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/80129
> * gimplify.c (gimplify_modify_expr_rhs) <case COND_EXPR>: Clear
> TREE_READONLY on result if writing it more than once.
>
> * g++.dg/torture/pr80129.C: New test.
>
> --- gcc/gimplify.c.jj 2017-03-21 07:56:55.000000000 +0100
> +++ gcc/gimplify.c 2017-03-21 13:37:45.555612652 +0100
> @@ -5098,6 +5098,14 @@ gimplify_modify_expr_rhs (tree *expr_p,
> if (ret != GS_ERROR)
> ret = GS_OK;
>
> + /* If we are going to write RESULT more than once, clear
> + TREE_READONLY flag, otherwise we might incorrectly promote
> + the variable to static const and initialize it at compile
> + time in one of the branches. */
> + if (VAR_P (result)
> + && TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node
> + && TREE_TYPE (TREE_OPERAND (cond, 2)) != void_type_node)
> + TREE_READONLY (result) = 0;
> if (TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node)
> TREE_OPERAND (cond, 1)
> = build2 (code, void_type_node, result,
> --- gcc/testsuite/g++.dg/torture/pr80129.C.jj 2017-03-21 13:40:04.179852313
> +0100
> +++ gcc/testsuite/g++.dg/torture/pr80129.C 2017-03-21 13:41:32.121735570
> +0100
> @@ -0,0 +1,14 @@
> +// PR c++/80129
> +// { dg-do run }
> +// { dg-options "-std=c++11" }
> +
> +struct A { bool a; int b; };
> +
> +int
> +main ()
> +{
> + bool c = false;
> + const A x = c ? A {true, 1} : A {false, 0};
> + if (x.a)
> + __builtin_abort ();
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
