Getting the code after the preprocessor in MinGW

I'm using MinGW (in Code::Blocks) and am having a hard time finding the perameter to get it to output the code after the preprocessor replaces all the #defines. Will it also keep the comments in so I can find where my code starts and put all the #includes back?

My ultimate is to unravel the knot of a program obfuscated for the purposes of compression. Deobfuscate it as it were. Actually it occurs to me that there must be something like this out there. Any clues?

-E or -P IIRC