Preprocessor output
gcc -E file.c
or
g++ -E file.cpp
will do this for you. The -E switch forces the compiler to stop after the preprocessing phase, spitting all it’s got at the moment to standard output.
Note: Surely you must have some #include directives. The included files get preprocessed, too, so you might get lots of output.
For Visual C++ the switch is /E which spits the preprocessor output to screen.
You can also call the C Preprocessor directly.
cpp infile outfile
Check out man cpp
for more info.