On Wed, 30 Apr 2014, Richard Biener wrote:
>
> With no longer recording alias subsets using BINFOs we now emit
> bogus alias warnings for accessing empty bases. The following
> avoids this, accessing those with an incompatible alias-set is
> harmless.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, ok?
Ping.
> Thanks,
> Richard.
>
> 2014-04-30 Richard Biener <rguent...@suse.de>
>
> PR c++/61004
> * typeck.c (cp_build_indirect_ref): Do not emit strict-aliasing
> warnings for accessing empty classes.
>
> * g++.dg/diagnostic/pr61004.C: New testcase.
>
> Index: gcc/cp/typeck.c
> ===================================================================
> --- gcc/cp/typeck.c (revision 209928)
> +++ gcc/cp/typeck.c (working copy)
> @@ -2921,8 +2921,9 @@ cp_build_indirect_ref (tree ptr, ref_ope
> of the result is "T." */
> tree t = TREE_TYPE (type);
>
> - if (CONVERT_EXPR_P (ptr)
> - || TREE_CODE (ptr) == VIEW_CONVERT_EXPR)
> + if ((CONVERT_EXPR_P (ptr)
> + || TREE_CODE (ptr) == VIEW_CONVERT_EXPR)
> + && (!CLASS_TYPE_P (t) || !CLASSTYPE_EMPTY_P (t)))
> {
> /* If a warning is issued, mark it to avoid duplicates from
> the backend. This only needs to be done at
> Index: gcc/testsuite/g++.dg/diagnostic/pr61004.C
> ===================================================================
> --- gcc/testsuite/g++.dg/diagnostic/pr61004.C (revision 0)
> +++ gcc/testsuite/g++.dg/diagnostic/pr61004.C (working copy)
> @@ -0,0 +1,11 @@
> +// { dg-do compile }
> +// { dg-options "-O2 -Wall" }
> +
> +struct A{ };
> +struct B:A{};
> +void f(A const&);
> +int main()
> +{
> + B b;
> + f(b); // { dg-bogus "strict-aliasing" }
> +}
>
