Can't figure out seg fault - c

Question

Why do I keep getting a set fault when I try and pass -H in the command line as a flag? -h (help) is working perfectly but -H(header) messes up every single time.
I have a main function as well which calls parse_command_line by passing the argc & argc.
the bool is defined as bool header = false;
the file is char** file = NULL;
and the reason I have the file+=1; in the code is so that it compiles because I am using a makefile that changes all warnings into errors.
#include "parse.h" /* prototypes for exported functions */
#include "../main/unused.h"
#include <stdlib.h>
#include <getopt.h>
#include <stdio.h>
#include <stdint.h>
int
parse_command_line (int argc, char **argv, bool *header, char **file)
{
int oc = 0;
file += 1;
bool help = false;
struct option long_options[] =
{
{"header", no_argument, NULL, 'H'},
{"help", no_argument, NULL, 'h'},
{0, 0, 0, 0}
};
while ((oc = getopt_long(argc, argv, "+Hh", long_options, NULL)) != -1)
{
printf("The value of oc = %d\n", oc);
switch(oc)
{
case 'h':
help = true;
break;
case 'H':
printf("inside case H");
*header = true;
break;
case '?':
fprintf(stderr, "Unknown flag = -%c, type -h or --help for help!\n", optopt);
exit(EXIT_FAILURE);
break;
default:
break;
}
}
printf("Out of loop"); if (optind+1 != argc)
{
fprintf(stderr, "Uh oh, invalid input! Try again with -h or --help for help!\n");
exit(EXIT_FAILURE);
}
if (help)
{
printf("\nHaving some trouble? Let me show you the ropes!\n\n");
printf("Format: ydi <option(s)> mini-elf-file\n\n");
printf("Here's your options:\n");
printf("-h --help Display usage\n");
printf("-H --header Show the Mini-Elf header\n");
exit(1);
}
if (header)
{
printf("Inside HEader");
FILE *file;
uint16_t nums[6];
file = fopen(argv[optind], "r");
#define STRUCT_ITEMS 7
fread(nums, 16, 6, file);
int cur_print;
for (cur_print = 0; cur_print < STRUCT_ITEMS; cur_print++)
{
printf("%d ", nums[cur_print]);
}
}
return 0;
}
My parse.h file is as follows:
#ifndef __PARSE_COMMAND_LINE__
#define __PARSE_COMMAND_LINE__
#include <stdbool.h>
int parse_command_line (int argc, char **argv, bool *header, char **file);
#endif
There are other files such as elf.h and elf.c which I have not implemented and are not called at all at this point, which leads me to believe they are not going to be the problem and don't need to post the small 2 line files. My main function is as follows:
#include <stdio.h> /* standard I/O */
#include <stdlib.h>
#include "unused.h" /* UNUSED macro */
#include "../cmdline/parse.h" /* command line parser */
#include "../y86/elf.h" /* Mini-ELF format */
int
main (int argc UNUSED, char **argv UNUSED)
{
printf ("Congratulations, you have compiled your source code!\n");
bool header = false;
char **file = NULL;
parse_command_line (argc, argv, &header, file);
return 0;
}
And the file unused.h (because the compiler will make unused variables an error instead of warning) is as follows:
#ifndef __UNUSED__
#define __UNUSED__
#define UNUSED __attribute__ ((unused))
#endif

Answer 1

The code doesn't check the return value of fopen, which will be NULL in case of an error. Dereferencing NULL in the fread call causes a segfault.