[Bug tree-optimization/107451] Segmentation fault with vectorized code.

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107451

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The bug is in the testcase:
gcc -fsanitize=undefined,address -g -o /tmp/pr107451{,.c}; /tmp/pr107451
=================================================================
==2296364==ERROR: AddressSanitizer: stack-buffer-overflow on address
0x7ffca382d798 at pc 0x00000040148c bp 0x7ffca382d680 sp 0x7ffca382d678
READ of size 8 at 0x7ffca382d798 thread T0
    #0 0x40148b in dot /tmp/pr107451.c:9
    #1 0x4019f8 in main /tmp/pr107451.c:21
    #2 0x7f8c74de858f in __libc_start_call_main (/lib64/libc.so.6+0x2958f)
    #3 0x7f8c74de8648 in __libc_start_main@GLIBC_2.2.5
(/lib64/libc.so.6+0x29648)
    #4 0x4010f4 in _start (/tmp/pr107451+0x4010f4)

Address 0x7ffca382d798 is located in stack of thread T0 at offset 40 in frame
    #0 0x401922 in main /tmp/pr107451.c:19

  This frame has 2 object(s):
    [32, 40) 'x' (line 20) <== Memory access at offset 40 overflows this
variable
    [64, 72) 'y' (line 20)
HINT: this may be a false positive if your program uses some custom stack
unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /tmp/pr107451.c:9 in dot
Shadow bytes around the buggy address:
  0x1000146fdaa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdab0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdac0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdad0: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00
  0x1000146fdae0: 00 00 f3 f3 f3 f3 00 00 00 00 00 00 00 00 f1 f1
=>0x1000146fdaf0: f1 f1 00[f2]f2 f2 00 f3 f3 f3 00 00 00 00 00 00
  0x1000146fdb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdb10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdb20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdb30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000146fdb40: 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
==2296364==ABORTING

x[ix+1] or y[ix+1] when ix is 0 and x is &x in main or y &y in main
is an out of bounds access.