segfault退出（EXIT_FAILURE）但沒有錯誤（EXIT_FAILURE，...）

Question

我在程序中使用getopt_long（source here），並且在測試其行爲時給出無效的long選項（--stack-overflow）和I得到：

[marcoms@baguette16 btcwatch]$ ./btcwatch --stack-overflow 
Segmentation fault (core dumped) 

爲背景，其在getopt_long()循環，即：

while((opt = getopt_long(argc, 
         argv, 
         OPTSTRING, 
         long_options, 
         &longopt_i)) != -1) 
{ 

    ... 

    default: 
     exit(EXIT_FAILURE); 
     break; 

相反的：

error(EXIT_FAILURE, 0, "unknown option !?"); 

（該exit()SIGSEGV代碼S）

瘋狂的事情是，default不應（且不，根據gdb），執行。

gdb表明，它立即崩潰的getopt_long()電話，

(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 

但是，當它與error()代替exit()運行時，它繼續正常：

(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] 

在這一點上，我真的很難過。什麼可能導致段錯誤？當然，我可以使用error()而不是退出，但這是令人難以置信的不滿意。

Answer 1

的問題是，你的選擇陣列無法正常終止：

const struct option long_options[] = { 
      // ... 
      // This is the last element 
      { 
        .name = "verbose", 
        .has_arg = no_argument, 
        .flag = NULL, 
        .val = 'v' 
      } 
    }; 

getopt_long(3)要求選擇陣列全零終止，以便它知道數組有多大 - 發現你從未真正將數組大小傳遞給getopt_long。所以發生的事情是它走過陣列的末端，尋找終結者，然後開始讀取越界之外的內容，Valgrind正確地抱怨。未定義的行爲結果。

修復的方法是簡單的：

const struct option long_options[] = { 
      // ... 
      { 
        .name = "verbose", 
        .has_arg = no_argument, 
        .flag = NULL, 
        .val = 'v' 
      }, 

      // Array terminator 
      {0, 0, 0, 0} 
};