See what the preprocessor is doing

Question

Is there anyway to see what you code looks like after the preprocessor has done all the substitutions?

Answer 1

That depends on your compiler. With gcc, you would use:

gcc -E source.c

Answer 2

For gcc jus use the -E switch

gcc -E

-E Stop after the preprocessing stage; do not run the compiler proper. The output is in the form of preprocessed source code, which is sent to the standard output.

Answer 3

As an alternative to gcc -E, you can run cpp on your file.

Answer 4

Just a note about system headers (eg <stdio.h>): they are a pain when preprocessed.

gcc -E -nostdinc file.c or cpp -nostdinc file.c will not include expansion of system headers.

Answer 5

Eclipse C++ IDE (CDT) has macro exploration control, which can be used for:

• obtaining final macro expansion
• looking threw expansion process step-by-step

This is called Macro Exploration control.