Re: don't warn about uninitialized anonymous bitfields

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 3/7/07, Alexandre Oliva <aoliva@redhat.com> wrote:
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=229459
>
> When compiling code such as:
>
> // gcc -O2 -Wall -S uninit-anon-bitfield.c
>
> struct foo {
>   unsigned int a:16;
>   unsigned int b:11;
>   unsigned int :5;
> };
>
> extern struct foo bar;
>
> void foo(int a, int b)
> {
>   struct foo tmp;
>
>   tmp.a = a;
>   tmp.b = b;
>
>   bar = tmp;
> }
>
> GCC scalarizes tmp and then issues a warning about the use of the
> uninitialized annoymous bitfield.
>
> This patch silences the warning.  Bootstrapped and regtested on
> x86_64-linux-gnu.   Ok to install?

The middle-end parts are ok with the following change:

      DECL_IGNORED_P (var) = 0;
-
+      TREE_NO_WARNING (var) = TREE_NO_WARNING (base)
+       || (elt->element ? TREE_NO_WARNING (elt->element) : false);
    }

better write that as

 TREE_NO_WARNING (var) = TREE_NO_WARNING (base);
  if (elt->element
      && TREE_NO_WARNING (elt->element))
    TREE_NO_WARNING (var) = 1;

The C and C++ parts need approval from a respective maintainer.

Thanks,
Richard.