odd "warning C4127: conditional expression is constant" under VS2005

Question

I'm trying to compile LightZPng with warnings on level 4. I get a lot of C4127 on lines that are clearly not worthy of this warning. An example:

#define MAX_BITS 15
int values_per_bitlen[ MAX_BITS + 1 ];
for ( int i = 0; i <= MAX_BITS; ++i )    // C4127 is here
    values_per_bitlen[ i ] = 0;

How can this code be changed to avoid the warning other than #pragma?

Answer 1

There's a piece of code at the top of LightZ.cpp that goes like this:

#define for if (false) {} else for

That means your actual statement is:

#define for if (false) {} else for ( int i = 0; i <= MAX_BITS; ++i )

which is why you're getting the constant expression error (it's the false, not the i <= MAX_BITS as I thought).

Simply comment out or delete that line from the file (I can't actually figure out why they would do that).