Generic Stacks in C

Question

I am implementing generic stack in C and I am facing a problem in stackPop method. My struct is as follows:

\"Stack.h\" file

Answer 1

I think the best you could do is to return a pointer to popped data (as a void* since that's about the best you can do in C for a 'generic' function):

void* stackPop(Stack *s, void *elemAddr){
        void *source = (char *)s.elems + (s.logLength-1)*s.elemSize;
        memcpy(elemAddr,source,s.elemSize);
        s.logLength--;
        return elemAddr;
}

Note that the caller still needs to provide the memory and the address to pop the data into; if you want ed you could avoid that by having the function malloc() the memory:

void* stackPop(Stack *s){
        void *source = (char *)s.elems + (s.logLength-1)*s.elemSize;
        void *elemAddr = malloc(s.elemSize);
        // if (!elemAddr) handle_error();
        memcpy(elemAddr,source,s.elemSize);
        s.logLength--;
        return elemAddr;
}

Of course that would require the caller to free() it when it is no longer needed, and adds the minor complication of needing to handle the out of memory situation.