CODEWITHSUNDEEP
cstack
Jagdish
Jagdish

Reputation: 1922

Does a C function without any argument and return value require a stack to execute?

Does below function need any stack for execution? 

int a;
void func(void)
{
    a = 10;
}

Upvotes: 0

Views: 225

Answers (1)

Eric Postpischil
Eric Postpischil

Reputation: 223264

As long as a C compiler can see the definition of func, it can1 implement func without using any stack space. For example, where it sees a call to func, it can implement that by emitting an instruction or two to move 10 into a. That would achieve the same result as calling func as a subroutine, so the C rules permit a C implementation to implement a call to func in that way, and it does not use any stack space.

Generally, if the compiler could not see the definition of func, as when compiling another source file that calls func but does not define it, the compiler would have to issue a call instruction or something similar, and that would, at the least, push the return address onto the stack.

Additionally, if the routine being called were more complicated, the compiler might choose not to implement it inline or might not be able to do so. (For example, if func contained calls to itself, it is generally not possible for the compiler to implement it with inline code in all situations; the compiler will need to implement it with actual subroutine call instructions, which do use stack space.)

Footnote

1 Whether any particular compiler will implement func without using stack space is another matter, dependent on the compiler, the switches used to compile, and other factors.

Upvotes: 2

Related Questions