I'm using getopt_long
in a program (source here), and, when testing its behaviour when given a invalid long option (--stack-overflow
), and I get:
[marcoms@baguette16 btcwatch]$ ./btcwatch --stack-overflow
Segmentation fault (core dumped)
For context, its in the getopt_long()
loop, i.e.:
while((opt = getopt_long(argc,
argv,
OPTSTRING,
long_options,
&longopt_i)) != -1)
{
...
default:
exit(EXIT_FAILURE);
break;
Instead of:
error(EXIT_FAILURE, 0, "unknown option !?");
(The exit()
code SIGSEGV
s)
The crazy thing is, default
should not be (and is not, according to gdb
), executed.
gdb
shows that it crashes immediately on the getopt_long()
call,
(gdb) start --stack-overflow
Temporary breakpoint 1, main (argc=2, argv=0x7fffffffe598) at src/main.c:96
96 btcdbg("main()");
(gdb) s
btcdbg (fmt=0x403260 "main()") at src/btcutil.c:50
50 }
(gdb)
main (argc=2, argv=0x7fffffffe598) at src/main.c:118
118 const struct option long_options[] = {
(gdb)
211 api_err.err = false;
(gdb)
212 colour = false;
(gdb)
213 found_path = false;
(gdb)
214 fp = NULL;
(gdb)
215 n = 1.0;
(gdb)
216 newlp = NULL;
(gdb)
217 pn = argv[0];
(gdb)
218 reverse = false;
(gdb)
219 verbose = false;
(gdb)
221 strcpy(currcy, "USD");
(gdb)
223 setlocale(LC_ALL, ""); // sets the locale to the system's default
(gdb)
225 while((opt = getopt_long(
(gdb)
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7643e2c in __strncmp_sse2 () from /usr/lib/libc.so.6
But when it is run with error()
instead of exit()
, it proceeds normally:
(gdb) start --stack-overflow
Temporary breakpoint 1, main (argc=2, argv=0x7fffffffe598) at src/main.c:96
96 btcdbg("main()");
(gdb) s
btcdbg (fmt=0x4032a0 "main()") at src/btcutil.c:50
50 }
(gdb)
main (argc=2, argv=0x7fffffffe598) at src/main.c:118
118 const struct option long_options[] = {
(gdb)
211 api_err.err = false;
(gdb)
212 colour = false;
(gdb)
213 found_path = false;
(gdb)
214 fp = NULL;
(gdb)
215 n = 1.0;
(gdb)
216 newlp = NULL;
(gdb)
217 pn = argv[0];
(gdb)
218 reverse = false;
(gdb)
219 verbose = false;
(gdb)
221 strcpy(currcy, "USD");
(gdb)
223 setlocale(LC_ALL, ""); // sets the locale to the system's default
(gdb)
225 while((opt = getopt_long(
(gdb)
/home/marcoms/code/btcwatch/./btcwatch: unrecognized option '--stack-overflow'
232 btcdbg("got option '%c'", opt);
(gdb)
btcdbg (fmt=0x4032a8 "got option '%c'") at src/btcutil.c:50
50 }
(gdb)
main (argc=2, argv=0x7fffffffe598) at src/main.c:233
233 switch(opt) {
(gdb)
236 help(pn, optarg);
(gdb)
help (prog_nm=0x7fffffffe8d8 "/home/marcoms/code/btcwatch/./btcwatch", topic=0x0) at src/btcutil.c:69
69 btcdbg("help()");
(gdb)
btcdbg (fmt=0x403bfc "help()") at src/btcutil.c:50
50 }
(gdb)
help (prog_nm=0x7fffffffe8d8 "/home/marcoms/code/btcwatch/./btcwatch", topic=0x0) at src/btcutil.c:71
71 char currcies[][3 + 1] = {
(gdb)
101 char topics[][16] = {
(gdb)
117 if(!topic) {
(gdb)
118 bputs("Usage: "); bputs(prog_nm); bputs(" [OPTION]\n");
(gdb)
Usage: /home/marcoms/code/btcwatch/./btcwatch [OPTION]
119 bputs(
(gdb)
Get and monitor Bitcoin trade information
Options: Long options:
-C --compare comare current price with stored price
-S --store store current price
-a --all equivalent to -pbs
-b --buy print buy price
-c CURRENCY --currency=CURRENCY set conversion currency
-n AMOUNT --amount=AMOUNT set the amount to convert
-o --colour, --color enable use of colour
-p --ping check for a successful JSON response
-r --reverse convert currency to Bitcoin
-s --sell print sell price
-v --verbose increase verbosity
-h [topic] --help[=topic] print this help, or help designated by topic
use --help=topics for available topics
-V --version print version number
Report bugs to marco@scannadinari.co.uk
btcwatch home page: <https://github.com/marcoms/btcwatch>
142 exit(EXIT_SUCCESS);
(gdb)
[Inferior 1 (process 25752) exited normally]
At this point, I really am stumped. What could be causing the segfault? Of course, I could just use error()
instead of exit, but that's incredibly unsatisfying.