I am getting segmentation fault and i dont know why [closed] - c

Question

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 2 years ago.
Improve this question
I am writing a vm from a tutorial and I keep getting segmentation fault. gdb is not giving me any info accept for that it is in int main() but I see nothing wrong, of course I have a bad eye for things that are wrong so if one of you smart people can help me that would be great
vm.c (I fixed the indentation)
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
typedef struct OBJECT_t {
uint8_t type;
union {
uint8_t u8;
int8_t i8;
uint32_t u32;
int32_t i32;
void *ptr;
};
} OBJECT;
typedef struct STACK_t {
int top;
int size;
OBJECT *stack;
} STACK;
typedef uint8_t* (*instruction)(uint8_t *, STACK *);
STACK stack_new(int size) {
STACK s;
s.top = 0;
s.size = size;
s.stack = (OBJECT *)malloc(sizeof(OBJECT) * size);
return s;
}
int stack_push(STACK *s, OBJECT o){
s->stack[s->top++] = o;
return s->top;
}
OBJECT stack_pop(STACK *s){
return s->stack[--(s->top)];
}
OBJECT stack_peek(STACK *s) {
return s->stack[s->top - 1];
}
void usage(){
printf("usage: vm <file>\n");
exit(1);
}
uint8_t *load_file(char *filename) {
FILE *f;
int size;
uint8_t *code = NULL;
struct stat st;
if((f = fopen(filename, "r"))) {
fstat(fileno(f), &st);
code = (uint8_t *)malloc(st.st_size);
fread((void *)code, 1, st.st_size, f);
}else {
printf("ERROR: cannot open file %s\n", filename);
usage();
}
return code;
}
uint8_t *op_nop(uint8_t *ip, STACK *s){
return ip + 1;
}
uint8_t *op_push_char(uint8_t *ip, STACK *s){
OBJECT o;
o.type = 'c';
o.u8 = *(ip + 1);
stack_push(s, o);
return ip + 2;
}
uint8_t *op_emit(uint8_t *ip, STACK *s){
OBJECT o = stack_pop(s);
putchar(o.u8);
return ip + 1;
}
int main(int argc, char **argv){
uint8_t *code;
uint8_t *ip;
STACK data;
instruction ops[256];
if(argc != 2){
usage();
}
for(int i=0;i<256;i++){
ops[i] = op_nop;
}
ops['c'] = op_push_char;
code = load_file(argv[1]);
data = stack_new(1024);
ip = code;
while(*ip != 'h'){
ip = ops[*ip](ip, &data);
}
return 0;
}
my program
hello.sp
c
c!cdclcrcocwc coclclcecHeeeeeeeeeeeeeh
this is my gdb output
Program received signal SIGSEGV, Segmentation fault.
0x00000000004014a6 in main ()

Answer 1

after fixing the problems discussed in the comments to the question:
when compiling AND when linking, use the parameter: -ggdb3 Which will:
result in a much larger object files and much larger executable.
will have the maximum amount of information for the gdb debugger.
Among other things, gdb will then display the line numbers.
then use the bt command to display the back trace of the stack at the time of a crash, so you know exactly how the code got to the crash.