Buffer overflow detected (_FORTIFY_SOURCE)

[Haelwenn (lanodan) Monnier]

Distro: Gentoo
Version: 4.1

This should be reproducible with putting `-D_FORTIFY_SOURCE=3` in CFLAGS.

$ gcal
*** buffer overflow detected ***: terminated
Aborted (core dumped)
$ lldb -c '/var/crash/1685920461-203-gcal[15677]'
(lldb) target create --core "/var/crash/1685920461-203-gcal[15677]"
Core file '/var/crash/1685920461-203-gcal[15677]' (x86_64) was loaded.
(lldb) bt
* thread #1, name = 'gcal', stop reason = signal SIGABRT
  * frame #0: 0x00007fc54a218f3c 
libc.so.6`__pthread_kill_implementation(threadid=<unavailable>, signo=6, 
no_tid=<unavailable>) at pthread_kill.c:44:76
    frame #1: 0x00007fc54a1ca386 libc.so.6`__GI_raise(sig=6) at raise.c:26:13
    frame #2: 0x00007fc54a1b447b libc.so.6`__GI_abort at abort.c:79:7
    frame #3: 0x00007fc54a20cb37 libc.so.6`__libc_message(action=do_abort, 
fmt="") at libc_fatal.c:155:5
    frame #4: 0x00007fc54a2a9412 libc.so.6`__GI___fortify_fail(msg="") at 
fortify_fail.c:26:5
    frame #5: 0x00007fc54a2a7ca6 libc.so.6`__GI___chk_fail at chk_fail.c:28:3
    frame #6: 0x00007fc54a2a7556 libc.so.6`__strcpy_chk(dest="", src="", 
destlen=3) at strcpy_chk.c:30:5
    frame #7: 0x000055ddaa5ee64f gcal`month_name [inlined] strcpy(__dest=<unavailable>, 
__src="") at string_fortified.h:79:10
    frame #8: 0x000055ddaa5ee64a gcal`month_name(month=5) at utils.c:1361:4
    frame #9: 0x000055ddaa5bb905 gcal`main [inlined] eliminate_invalid_data at 
gcal.c:7339:27
    frame #10: 0x000055ddaa5bb5f9 gcal`main(argc=<unavailable>, 
argv=<unavailable>) at gcal.c:2825:3
    frame #11: 0x00007fc54a1b5350 
libc.so.6`__libc_start_call_main(main=(gcal`main at gcal.c:1580), argc=1, 
argv=0x00007fff73422348) at libc_start_call_main.h:58:16
    frame #12: 0x00007fc54a1b5400 libc.so.6`__libc_start_main_impl(main=(gcal`main at 
gcal.c:1580), argc=1, argv=0x00007fff73422348, init=<unavailable>, 
fini=<unavailable>, rtld_fini=<unavailable>, stack_end=0x00007fff73422338) at 
libc-start.c:360:3
    frame #13: 0x000055ddaa5b9575 gcal`_start + 37

Best regards