Can you define an array on the stack and pass the pointer to a global variable?

The Original Question

I’m programming C on a microchip that doesn’t support any memory allocation commands, but it does like pointers (of course). So my question is:

Is there a way to define an array within a function, and pass the pointer to that array back to a global variable?

This would be a way to have a dynamic memory use WITHOUT malloc, realloc, or calloc. Essentially stack memory being passed back to global WITHOUT it destroying itself. I’m assuming that the alloc commands are specifically needed to ensure it doesn’t get destroyed, but I wanted to check and see if there was a way around this.

My Answer

The main problem is function calls and how calls affect stack. On IBM architecture, simply, current EBP pushed to stack, caller stack frame is saved to EBP and callee parameters pushed to stack(generally). On return pushed EBP is poped and stack allocated parameters could be overwritten by caller, that area is free to use since callee is returned.

When you some how dynamically allocate some space on stack, it’s a possibility to overwrite that space somewhere in time at a function call which has some wide veriaty of parameters or recursive calls. This is why all dynamic allocations happens in Heap and heap management is at the hands of operating system. Since malloc (etc) is o.s. wrappers for heap allocations you do not need to worry about that management, o.s. will take it care for you.

If you want to achieve dynamic allocations on stack you need to go with assembly. Make sure allocate enough space before a function call at the caller site and take that space back when caller will be returned to its caller. And that organisation would be a brainfk i guess..

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