alt Hacker NewsI honestly can't tell if you know a lot more than me or a lot less than me about how computers work... A couple of honest questions:
1. Where do you save the current value of the return address register before calling a function?
2. When parameters are "grouped into a structure" and the structure is passed as an argument to a function, where do you store that structure?
Replies
quietbritishjim • last Tuesday at 12:25 AM
The sibling comment already answered your question, but just to add: As I mentioned earlier, this was actually how old programming languages worked. Famously(ish), Dijkstra secretly snuck recursive functions into the ALGOL 60 standard, thus forcing compiler authors to use a stack!
Not OP, but presumably, the answers are:
1) You don't... hence, my question about no nested function calls. If you push it anywhere else, you can call it whatever you want, but you just re-invented the stack. I _guess_ you could do some wierd stuff to technically not get a stack, but... again, it's wierd. And for what, again?
2) Some fixed address. If you have for example:
```c
typeRealBigStructure foo;
void baz(typeRealBigStructure * struct){
}void bar(void){
}```
The foo will probably end up in the BSS and will take up that space for the whole lifetime of the program. That's not the heap, not the stack, just... a fixed location in memory where the linker placed it.
I guess on big PC's stuff is very dynamic and you use malloc for a lot of stuff, but in embedded C, it's a very common pattern.