[Bug sanitizer/107431] UBSan has inconsistent behaviors in certain code snippet

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107431

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
> % cat example2.c
> int main() {
>     int a=2;
>     int b=1;
>     long *c = &b;
>     long d = *c;
>     &a;
> }

Well, in this case you are lucky and 'b' is aligned to 8-bytes:
    __builtin_printf ("&b=%p\n", &b);

$ gcc-12 example2.c -fsanitize=undefined -w && ./a.out
&b=0x7fffffffd438

$ gcc-12 -O1 example2.c -fsanitize=undefined -w && ./a.out
&b=0x7fffffffd44c
example2.c:6:10: runtime error: load of misaligned address 0x7fffffffd44c for
type 'long int', which requires 8 byte alignment
0x7fffffffd44c: note: pointer points here
  67 6c 69 62 01 00 00 00  68 d5 ff ff ff 7f 00 00  b0 c5 62 f7 ff 7f 00 00  50
d5 ff ff ff 7f 00 00
              ^ 
example2.c:6:10: runtime error: load of address 0x7fffffffd44c with
insufficient space for an object of type 'int'
0x7fffffffd44c: note: pointer points here
  67 6c 69 62 01 00 00 00  68 d5 ff ff ff 7f 00 00  b0 c5 62 f7 ff 7f 00 00  50
d5 ff ff ff 7f 00 00
              ^ 

So nothing we can do about it.