==21400==ERROR: AddressSanitizer: heap-use-after-free on address 0x621000002908 at pc 0x55be55dfed00 bp 0x7ffe2e87ab60 sp 0x7ffe2e87ab50
READ of size 8 at 0x621000002908 thread T0
    #0 0x55be55dfecff in _obstack_free lib/obstack.c:273
    #1 0x55be55b96997 in gram_lex /Users/akim/src/gnu/bison/src/scan-gram.l:614
    #2 0x55be55aa48c6 in gram_parse src/parse-gram.c:2067
    #3 0x55be55b15c4e in reader src/reader.c:712
    #4 0x55be558c0dca in main src/main.c:108
    #5 0x7f9d017ebb96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #6 0x55be558c48e9 in _start (/mnt/hda2/suhwan/add_project/final/FINAL_TEST_ZONE/program/bison-3.7/install_dir/bin/bison+0x388e9)

0x621000002908 is located 8 bytes inside of 4064-byte region [0x621000002900,0x6210000038e0)
freed by thread T0 here:
    #0 0x7f9d01c997a8 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xde7a8)
    #1 0x55be55dfe52a in call_freefun lib/obstack.c:98
    #2 0x55be55dfe52a in _obstack_free lib/obstack.c:274

previously allocated by thread T0 here:
    #0 0x7f9d01c99b40 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdeb40)
    #1 0x55be55df3880 in xmalloc lib/xmalloc.c:53

SUMMARY: AddressSanitizer: heap-use-after-free lib/obstack.c:273 in _obstack_free
Shadow bytes around the buggy address:
  0x0c427fff84d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8500: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff8510: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c427fff8520: fd[fd]fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c427fff8530: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c427fff8540: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c427fff8550: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c427fff8560: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c427fff8570: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
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
==21400==ABORTING