On Thu, 24 Jun 2021, Jakub Jelinek wrote:
> Hi!
>
> finish_bitfield_representative has an early out if the field after a
> bitfield has error_mark_node type, but that early out leads to TREE_TYPE
> of the DECL_BIT_FIELD_REPRESENTATIVE being NULL, which breaks assumptions
> on code that uses the DECL_BIT_FIELD_REPRESENTATIVE during error-recovery.
>
> The following patch instead sets TREE_TYPE of the representative to
> error_mark_node, something the users can deal with better. At this point
> the representative can be set as DECL_BIT_FIELD_REPRESENTATIVE for multiple
> bitfields, so making sure that we clear the DECL_BIT_FIELD_REPRESENTATIVE
> instead would be harder (but doable, e.g. with the error_mark_node TREE_TYPE
> set by this patch set some flag in the caller and if the flag is there, walk
> all the fields once again and clear all DECL_BIT_FIELD_REPRESENTATIVE that
> have error_mark_node TREE_TYPE).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2021-06-24 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/101172
> * stor-layout.c (finish_bitfield_representative): If nextf has
> error_mark_node type, set repr type to error_mark_node too.
>
> * gcc.dg/pr101172.c: New test.
>
> --- gcc/stor-layout.c.jj 2021-06-21 09:39:21.798485474 +0200
> +++ gcc/stor-layout.c 2021-06-23 11:10:22.617680051 +0200
> @@ -2086,7 +2086,10 @@ finish_bitfield_representative (tree rep
> /* If there was an error, the field may be not laid out
> correctly. Don't bother to do anything. */
> if (TREE_TYPE (nextf) == error_mark_node)
> - return;
> + {
> + TREE_TYPE (repr) = error_mark_node;
> + return;
> + }
> maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
> DECL_FIELD_OFFSET (repr));
> if (tree_fits_uhwi_p (maxsize))
> --- gcc/testsuite/gcc.dg/pr101172.c.jj 2021-06-23 11:15:19.934670004
> +0200
> +++ gcc/testsuite/gcc.dg/pr101172.c 2021-06-23 11:15:07.255841009 +0200
> @@ -0,0 +1,20 @@
> +/* PR middle-end/101172 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +union U
> +{
> + int a[3];
> + struct
> + {
> + int a : 3;
> + struct this_struct var; /* { dg-error "field 'var' has incomplete type"
> } */
> + } b;
> +};
> +
> +const union U hello = {.a = {1, 2, 3}};
> +
> +void foo()
> +{
> + int x = hello.b.a;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
