[Bug sanitizer/99418] sanitizer checks for accessing multidimentional VLA-array

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99418

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-03-08
             Status|UNCONFIRMED                 |WAITING
     Ever confirmed|0                           |1

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
> Surprisingly if I replace taking a reference with writing to the array it
> will show an error.

Yes, ASAN instruments memory reads and writes, so your test-case reports ASAN
errors with:

void escape(int &a)
{
  a = 123;
}

$ g++ pr99418.C -fsanitize=address && ./a.out 
=================================================================
==7912==ERROR: AddressSanitizer: dynamic-stack-buffer-overflow on address
0x7fffffffde90 at pc 0x000000400869 bp 0x7fffffffde10 sp 0x7fffffffde08
WRITE of size 4 at 0x7fffffffde90 thread T0
    #0 0x400868 in escape(int&)
(/home/marxin/Programming/testcases/a.out+0x400868)
    #1 0x4009c0 in test(unsigned long, unsigned long)
(/home/marxin/Programming/testcases/a.out+0x4009c0)
    #2 0x400a06 in main (/home/marxin/Programming/testcases/a.out+0x400a06)
    #3 0x7ffff708db24 in __libc_start_main (/lib64/libc.so.6+0x27b24)
    #4 0x40077d in _start (/home/marxin/Programming/testcases/a.out+0x40077d)

Address 0x7fffffffde90 is located in stack of thread T0
SUMMARY: AddressSanitizer: dynamic-stack-buffer-overflow
(/home/marxin/Programming/testcases/a.out+0x400868) in escape(int&)
Shadow bytes around the buggy address:
  0x10007fff7b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7b90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7ba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7bb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7bc0: 00 00 00 00 00 00 00 00 ca ca ca ca 00 00 00 00
=>0x10007fff7bd0: 00 00[cb]cb cb cb cb cb 00 00 00 00 00 00 00 00
  0x10007fff7be0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7bf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7c10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7c20: 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
  Shadow gap:              cc
==7912==ABORTING

That said, can we close it as resolved?