cat ubsan.c && gcc ubsan.c -fsanitize=address -g && ./a.out
int main(int argc, char **argv)
{
  int *items = (int[]) {1, 2, 3};

  switch (argc)
  {
  case 0:
    items = (int[]) {999};
    break;
  default:
    items = (int[]) {999, 888};
    break;
  }

  return items[0];
}
=================================================================
==17838==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fffffffdbc0 at pc 0x0000004013e5 bp 0x7fffffffdb50 sp 0x7fffffffdb48
READ of size 4 at 0x7fffffffdbc0 thread T0
    #0 0x4013e4 in main /tmp/ubsan.c:15
    #1 0x7ffff73b8b7a in __libc_start_main ../csu/libc-start.c:308
    #2 0x4010a9 in _start (/tmp/a.out+0x4010a9)

Address 0x7fffffffdbc0 is located in stack of thread T0 at offset 64 in frame
    #0 0x401161 in main /tmp/ubsan.c:2

  This frame has 3 object(s):
    [48, 52) '<unknown>'
    [64, 72) '<unknown>' <== Memory access at offset 64 is inside this variable
    [96, 108) '<unknown>'
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-use-after-scope /tmp/ubsan.c:15 in main
Shadow bytes around the buggy address:
  0x10007fff7b20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7b30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7b40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7b50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7b60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10007fff7b70: f1 f1 f1 f1 f1 f1 f8 f2[f8]f2 f2 f2 00 04 f3 f3
  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 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
==17838==ABORTING