Detecting 64bit compile in C

Question

is there a C macro or some kind of way that i can check if my c program was compiled as 64bit or 32bit at compile time in C?

Compiler: GCC Operating systems that i n

Answer 1

An easy one that will make language lawyer squeem.

if(sizeof (void *) * CHARBIT == 64) {
...
}
else {
...
}

As it is a constant expression an optimizing compiler will drop the test and only put the right code in the executable.