My function is being passed a struct containing, among other things, a NULL terminated array of pointers to words making up a command with arguments.

I'm performing a glob match on the list of arguments, to expand them into a full list of files, then I want to replace the passed argument array with the new expanded one.

The globbing is working fine, that is, g.gl_pathv is populated with the list of expected files. However, I am having trouble copying this array into the struct I was given.

#include <glob.h>

struct command {
  char **argv;
  // other fields...
}

void myFunction( struct command * cmd )
{
  char **p = cmd->argv;
  char* program = *p++; // save the program name (e.g 'ls', and increment to the first argument

  glob_t g;
  memset(&g, 0, sizeof(g));
  g.gl_offs = 1;
  int res = glob(*p++, GLOB_DOOFFS, NULL, &g);
  glob_handle_res(res);
  while (*p)
  {
      res = glob(*p, GLOB_DOOFFS | GLOB_APPEND, NULL, &g);
      glob_handle_res(res);
  }

  if( g.gl_pathc <= 0 )
  {
      globfree(&g);
  }

  cmd->argv = malloc((g.gl_pathc + g.gl_offs) * sizeof *cmd->argv);

  if (cmd->argv == NULL) { sys_fatal_error("pattern_expand: malloc failed\n");}
   // copy over the arguments
  size_t i = g.gl_offs;
  for (; i < g.gl_pathc + g.gl_offs; ++i)
      cmd->argv[i] = strdup(g.gl_pathv[i]);

  // insert the original program name
  cmd->argv[0] = strdup(program);
  ** cmd->argv[g.gl_pathc + g.gl_offs] = 0; **
  globfree(&g);
}

void 
command_free(struct esh_command * cmd)
{
    char ** p = cmd->argv;
    while (*p) {
        free(*p++); // Segfaults here, was it already freed?
    }
    free(cmd->argv);
    free(cmd);
}

Edit 1: Also, I realized I need to stick program back in there as cmd->argv[0]
Edit 2: Added call to calloc
Edit 3: Edit mem management with tips from Alok
Edit 4: More tips from alok
Edit 5: Almost working.. the app segfaults when freeing the command struct

Finally: Seems like I was missing the terminating NULL, so adding the line:

cmd->argv[g.gl_pathc + g.gl_offs] = 0;  

seemed to make it work.