#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>

 

__attribute__((constructor)) void enter_namespace(int argc, char *argv[]) {
    struct option long_options[] = {
        {"some-option", required_argument, 0, 's'},
        {0,0,0,0}
    };

    int option_index, c, pid;
    while ((c = getopt_long_only(argc, argv, "m:", long_options, &option_index)) != -1) {
        switch (c) {
            case 's':
                pid = atoi(optarg);
                if (pid < 1) {
                    fprintf(stderr, "Invalid some-option: %s\n", optarg);
                    exit(1);
                }
                break;
            case 0:
                break;
        }
    }
}

 

int main(void) {
  return 0;
}
```

 

Run with or without options will segfault frequently:
```

~ # gcc -g test.c 
~ # ./a.out 
Segmentation fault
~ # ./a.out 
~ # ./a.out 
~ # ./a.out 
~ # ./a.out 
Segmentation fault
~ # 
~ # gdb ./a.out
GNU gdb (GDB) 7.12.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-alpine-linux-musl".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./a.out...done.
(gdb) r
Starting program: /root/a.out 
warning: Error disabling address space randomization: Operation not permitted
During startup program terminated with signal SIGSEGV, Segmentation fault.
(gdb) bt
No stack.
(gdb) 
```

It appears that having any code in a constructor function leads to this problem, having the same code in the main function does not segfault.

I'm not sure how to take this any further without a backtrace.

I am using musl 1.1.16-r14 on alpine 3.6.0. The code above works with glibc.

Regards,

Bracken Dawson.