gcc 12 question

[Patrick Welche <prlw1%talktalk.net@localhost>]

I'm trying to build a release on amd64 using

HAVE_MESA_VER=21
HAVE_GCC=12

and get the following build error which I am puzzled by:

    inlined from 'r300_merge_textures_and_samplers' at /usr/xsrc/external/mit/MesaLib/dist/src/gallium/drivers/r300/r300_state_derived.c:823:17,
    inlined from 'r300_update_derived_state' at /usr/xsrc/external/mit/MesaLib/dist/src/gallium/drivers/r300/r300_state_derived.c:1064:9:
/usr/xsrc/external/mit/MesaLib/dist/src/gallium/drivers/r300/r300_state_derived.c:676:5: error: 'util_format_unswizzle_4f' reading 4 bytes from a region of size 0 [-Werror=stringop-overread]
  676 |     util_format_unswizzle_4f(border_swizzled, border, desc->swizzle);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/xsrc/external/mit/MesaLib/dist/src/gallium/drivers/r300/r300_state_derived.c:676:5: note: referencing argument 3 of type 'const unsigned char[4]'
In file included from /usr/xsrc/external/mit/MesaLib/dist/src/gallium/auxiliary/util/u_pack_color.h:40,
                 from /usr/xsrc/external/mit/MesaLib/dist/src/gallium/drivers/r300/r300_state_derived.c:28:
/usr/xsrc/external/mit/MesaLib/dist/src/util/format/u_format.h: In function 'r300_update_derived_state':
/usr/xsrc/external/mit/MesaLib/dist/src/util/format/u_format.h:1671:6: note: in a call to function 'util_format_unswizzle_4f'
 1671 | void util_format_unswizzle_4f(float *dst, const float *src,
      |      ^~~~~~~~~~~~~~~~~~~~~~~~


desc is a const struct util_format_description *

util/format/u_format.h:226 defines the swizzle member of
util_format_description as:

unsigned char swizzle[4];

and the truncated quote of util/format/u_format.h:1671 is

void util_format_unswizzle_4f(float *dst, const float *src,
                              const unsigned char swz[4]);

so all is consistent.

error: 'util_format_unswizzle_4f' reading 4 bytes from a region of size 0 [-Werror=stringop-overread]

Assuming "a region" is the 3rd argument, then how can the size of an
unsigned char[4] be zero?

Puzzled...


Cheers,

Patrick