No protection when stack resource is depleted (eg a bad recursion)

[SleepyRoy]

V version:
V playground

OS:
N/A

What did you do?

// A trivial recursive function just for testing
// Return 1 if works normally
fn func(n int) int {
    if n>1{
    	return func(n-1)
    }
    else{
    	return 1
    }
}

fn main() {
    println(func(1000000))  // Make n really large so that stack is depleted
} 

What did you expect to see?
An error: a bad recursion.

What did you see instead?
You just found a bug. V can't compile this program, but it should. Please create a GitHub issue.

Some compilers set a default limit and allow users to change it when necessary. Should we also introduce some mechanism to solve this in V?

[Metalymph]

In this case i think two things can be applied:

• a check for available stack memory after each recursive function call (which is identified by a bool is_rec for example). So, this check would be applied only for this kind of functions and would verify if stack memory limit (assigned by default, or manually assigned for example with a command option like v -sl 64000 file.v) is been exceeded than return error 'Stack Overflow'.
• an optimization for tail recursions (only for future optimizer)

Could be a good solution ? @medvednikov

[dumblob]

I'd leave this backend specific - each C backend has some limitations and V shouldn't try to unify that. Of course, for the direct x86 backend V plans to have at some point a clearly defined value is necessary, but that's not what this issue is about here.

In other words, V compiler shall understand from the backend compiler, that the backend compiler complained about stack depth and shall print a better message than the currently incorrect one:

You just found a bug. V can't compile this program, but it should. Please create a GitHub issue.

[medvednikov]

Yeah, not something that can be handled by V.