Unable to return NULL in a function that expects an integer return type
c
Solution
If the return type is `int`, you can't return a `NULL`. To show an error, you could instead return a special value like zero or -1, if you check for that value in any calling function. Lots of functions return nonnegative numbers on success, or -1 on error.
`NULL` cannot be stored in an `int` variable, unlike in SQL, for example. If you ignore the warning and return `NULL` anyway, then `NULL` will be casted to zero. The calling function won't be able to tell whether you returned `NULL` or zero.
If your function only needs to indicate success or failure, then it's common to return 1 for success, and zero for failure. Zero means "false" when treated as a boolean value (like in `if` statements), and non-zero means "true."
Problem
Warning: return makes integer from pointer without a cast [enabled by default] return NULL; I am trying to return NULL in my fucntion, but it's not working out and I don't understand why it is so. Below is my code, but I will not post the entire thing since I am only having problems with the return statement. I hope you can understand. ``` #include<stdio.h> #include<stdlib.h> #include<math.h> typedef struct { int* data; unsigned int len; } intarr_t; int intarr_save_binary( intarr_t* ia, const char* filename ) { if(ia == NULL) { return NULL; // problem here, I want to return NULL if intarr_t*ia is null } else { // remaining code here, but is uncessary return 0; } } ``` My final question is also how do I check if the char array filename is NULL? Would I do this: ``` if (filename == NULL) { return NULL; } ```