$ ./strfunc-test 
Assertion failed: VALID(buffer), file trio.c, line 3941
IOT/Abort trap (core dumped)
$ dbx .libs/lt-strfunc-test ./core
dbx version 5.1
Type 'help' for help.
Core file created by program "lt-strfunc-test"

thread 0x4 signal IOT/Abort trap at >*[__nxm_thread_kill,
0x3ff8057d818]        ret     zero, (ra), 1
(dbx) where
>  0 __nxm_thread_kill(0x6, 0x20000a0fc40, 0x3ff80576618, 0x3ffc0184000,
0x3ffc0184000) [0x3ff8057d818]
   1 pthread_kill(0x0, 0x11fffb238, 0x0, 0x11fffc010, 0x1) [0x3ff80576630]
   2 (unknown)() [0x3ff80581bd8]
   3 (unknown)() [0x3ff807e3aa0]
   4 exc_raise_signal_exception(0x60ffe0003, 0x86, 0x0, 0x3ff8057d818, 0x1)
[0x3ff807e3e90]
   5 (unknown)() [0x3ff80578110]
   6 __nxm_thread_kill(0x6, 0x20000a0fc40, 0x3ff80576618, 0x3ffc0184000,
0x3ffc0184000) [0x3ff8057d818]
   7 pthread_kill(0x11fffbe60, 0x11fffbe6d, 0x0, 0x0, 0x1) [0x3ff80576630]
   8 (unknown)() [0x3ff8058daf8]
   9 __tis_raise(0x1, 0x0, 0x3ff8013b4d8, 0x6, 0x3ff801a20d4)
[0x3ff8013b4d4]
  10 raise(0x3ff8013b4d8, 0x6, 0x3ff801a20d4, 0x3ff00000000, 0x3ff801c53d4)
[0x3ff801a20d0]
  11 abort(0x3ff801c4e84, 0x11fffbe60, 0x3ff80577e70, 0x0, 0x600000000)
[0x3ff801c53d0]
  12 __assert(0x3ff800bf780, 0x3ff800bf770, 0x1, 0x1, 0x1) [0x3ff801c4e80]
  13 _g_trio_vsnprintf(0x3ffbffebec4, 0x140030b80, 0x11fffbf60,
0x3ff00000018, 0x0) [0x3ffbfff5590]
  14 g_vsnprintf(0x0, 0x140009798, 0x3ffbffebbdc, 0x11fffbf60,
0x3ff00000018) [0x3ffbffebec0]
  15 g_snprintf(0x0, 0x0, 0x140009798, 0x1400097a0, 0xffffffffffffffff)
[0x3ffbffebbd8]
  16 main(argc = 1, argv = 0x11fffc018) ["strfunc-test.c":450, 0x1200095a4]
(dbx)