[Bug sanitizer/106368] New: ASan fails to report an error.

["shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106368

            Bug ID: 106368
           Summary: ASan fails to report an error.
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org
  Target Milestone: ---

Hi,

For the following code snippet, `gcc-trunk -O0 -fsanitize=address` reports
nothing but `gcc-trunk -O3` reports it.

$ cat a.c
#pragma pack(1)
struct a {
  int b;
  long c
};
#pragma pack()
struct d {
  long b;
  struct a c
};
struct d f;
static long *g = &f.c.c;
int main() {
    volatile int e = *(g+1);
}
$
$gcc-trunk -O0 -fsanitize=address a.c && ./a.out
$
$gcc-trunk -O3 -fsanitize=address a.c && ./a.out
================================================================
==1==ERROR: AddressSanitizer: unknown-crash on address 0x000000404134 at pc
0x0000004011a8 bp 0x7ffeadf39d20 sp 0x7ffeadf39d18
READ of size 8 at 0x000000404134 thread T0
    #0 0x4011a7 in main /app/example.c:14
    #1 0x7f044e5530b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x240b2) (BuildId:
9fdb74e7b217d06c93172a8243f8547f947ee6d1)
    #2 0x40120d in _start (/app/output.s+0x40120d) (BuildId:
a4a82ec9bae1cc563083aff345004ea80e8df0db)

0x000000404138 is located 0 bytes to the right of global variable 'f' defined
in '/app/example.c:11:10' (0x404120) of size 24
SUMMARY: AddressSanitizer: unknown-crash /app/example.c:14 in main
Shadow bytes around the buggy address:
  0x0000800787d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000800787e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000800787f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078810: 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
=>0x000080078820: 00 00 00 00 00 00[00]f9 f9 f9 f9 f9 00 00 00 00
  0x000080078830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078840: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078850: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078860: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x000080078870: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==1==ABORTING