Stack overflow from local variables?

Question

Let me start by saying my question is not about stack overflows but on way to make it happen, without compile-time errors\warnings. I know (first hand) you can overflow a stack with recursion:

void endlessRecursion()
{
    int x = 1;
    if(x) endlessRecursion(); //the 'if' is just to hush the compiler
}

My question is, is it possible to overflow the stack by declaring too many local variables. The obvious way is just declare a huge array like so:

void myStackOverflow()
{
    char maxedArrSize[0x3FFFFFFF];  // < 1GB, compiler didn't yell
} 

In practice even 0xFFFFF bytes causes stack overflow on my machine

So, I was wondering:

1. Since I haven't tried it, if I declare enough variables would the stack overflow?
2. Is there a way to use the preprocessor or other compile-time "tools" (like C++ template meta-programming) to do the first thing, i.e. make it declare a lot of local variables, by somehow causing it to loop? if so, how?
3. This is theoretical - Is there a way to know if the a program's stack would overflow at compilation time? and if so, please explain.

Answer 1

Yes, allocating a large amount of memory will cause a stack overflow. It shouldn't matter whether you allocate one large variable or a lot of small ones; the total size is what's relevant.

You can't do a compile-time loop with the preprocessor, but you can implement some shortcuts that let you generate large amounts of code without typing it all. For example:

#define DECLARE1 { int i;
#define END1 }

#define DECLARE2 DECLARE1 DECLARE1
#define END2 END1 END1

#define DECLARE4 DECLARE2 DECLARE2
#define END4 END2 END2

and so on. This puts the multiple int i; declarations in nested blocks, ensuring that all the objects exist at the same time while avoiding name conflicts. (I couldn't think of a way to give all the variables distinct names.)

DECLARE4 END4

expands to:

{ int i; { int i; { int i; { int i; } } } }

This won't work if your compiler imposes a limit on the length of a line after preprocessing.

The lesson here is that the preprocessor isn't really designed for this kind of thing. It's much easier and more flexible to write a program in your favorite scripting language that generates the declarations. For example, in bash:

for i in {1..100} ; do
    echo "    int i$i;"
done