https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120780
--- Comment #11 from Siddhesh Poyarekar <siddhesh at gcc dot gnu.org> ---
OK, so we don't really need a FAM based reproducer either, here's one without
it. FAM just makes this case more likely because due to it, __bdos succeeds
more often in the kernel code:
typedef __SIZE_TYPE__ size_t;
struct inner
{
int dummy;
};
struct container
{
int mcast_rate[6];
struct inner mesh;
};
extern void __warn (void)
__attribute__ ((__warning__ ("__builtin_dynamic_object_size failed")));
static void
child (struct inner *ifmsh)
{
struct container *sdata =
(struct container *) ((void *) ifmsh
- __builtin_offsetof (struct container, mesh));
if (__builtin_dynamic_object_size(sdata->mcast_rate, 1)
!= sizeof (sdata->mcast_rate))
__warn ();
}
int
parent (size_t sz)
{
struct container *sdata = __builtin_malloc (sz);
struct inner *ifmsh = &sdata->mesh;
child (ifmsh);
}
$ gcc/cc1 -fdump-tree-objsz-details -std=gnu17 -quiet -O2 -o /dev/null -Werror
../cfg-min.c
In function ‘child’,
inlined from ‘parent’ at ../cfg-min.c:34:3:
../cfg-min.c:26:5: error: call to ‘__warn’ declared with attribute warning:
__builtin_dynamic_object_size failed [-Werror=attribute-warning]
26 | __warn ();
| ^~~~~~~~~
cc1: all warnings being treated as errors
