如何在没有内存泄漏的情况下正确分配 char[]

Question

How do I fix this line to work with my code. I know in C99 variable-length arrays are allowed, but I need to use malloc to fix this line. How would I go about doing that. char stack[strlen(input)]; (I am not using C99, by the way)

Answer 1

Declare stack as pointer and use malloc .

char *stack = malloc(strlen(input));

Don't forget to free the memory.

Answer 2

Allow me to add that it's recommended to always check the value of a pointer you just allocated with malloc.

You can do it this way :

char *stack = malloc(strlen(input));
if (stack == NULL) {
  return -1;
}

You can modify the return -1; with whatever you want depending where you are using this part of code. -1 being what some people usually return when an error occurs.

Why do that?

The malloc() function can fail allocating memory space in case RAM is full for example. This doesn't happen often but it has to be catched for code correctness.