Segmentation Fault when attempting to print value in C

Question

The following C code returns a \"segmentation fault\" error. I do not understand why it does not return the value 20. What is my error?

#include 

        

Answer 1

You haven't allocated space for your int, you've only declared a pointer to an int.

The pointer is uninitialized, and so writing to that unknown space in memory is undefined behavior and causes problems. This typically causes a segfault.

You can allocate a slot for an integer using malloc:

n = malloc(sizeof(int));

And use a corresponding call to free to free up the memory later:

free(n);

But allocating a single slot for an integer is pretty unusual, typically you would allocate the int on the stack:

int n;
n = 20;