https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92380
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |msebor at gcc dot gnu.org
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning was introduced in r275981 which was an enhancement to detect more
instances of inadvertent accesses past the end of struct members. It might be
possible to relax the warning to handle some of these cases but I'm not
convinced it's a good idea or worth the trouble for code that does these sorts
of type-punning tricks.
I suggest to rewrite the code in a more straightforward way and without the
casts, e.g., like so:
char *t1 (outer_struct *p, char str[240])
{
char *q = (char*)p + sizeof *p - (sizeof(inner_large_struct) -
sizeof(inner_small_struct)) + offsetof (flexarr_struct, s);
__builtin_strcpy (q, str);
return q;
}
When starting with a pointer to the the enclosing object GCC treats as valid
accesses to the whole object if it's known (or to the largest array of such
objects when it isn't). Otherwise, only accesses to the same member are
considered valid when using a pointer derived from the address of that member.
