CODEWITHSUNDEEP
cpointers
Django
Django

Reputation: 181

Pointer-to-a-pointer in C throws segmentation fault

This might sound pretty old school, but I'm still unable to figure out why the following program throws a segmentation fault. Any help would be great

#include <stdio.h>
pointer(char **x)
{
    printf ("Before %c",*x[0]);
    *x[0] = 'a';   // segmentation fault here!!
    printf ("After %c", *x[0]);
}
int main()
{
    char *x = "Hello";
    pointer(&x);
}

Upvotes: 1

Views: 73

Answers (2)

Asics
Asics

Reputation: 868

char *x = "Hello";

This declaration makes it read-only. Writing to it the way you tried is illegal.

See this for more information

Upvotes: 1

AntonH
AntonH

Reputation: 6437

It's explained in the answer to this question.

TL;DR: the memory pointed to by char *x = "Hello"; is read only. Trying to write to it is illegal, and will result in a segmentation fault.

Upvotes: 1

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