How to find a declaration of a variable/function in c code?

Question

Maybe it is a dummy question but for a long time I have been trying to read a C code written by others and each time unsuccessfully. When reading the code I stumble upon some macros or a function declaration of which I am just unable to find as they come from another libraries where it is not obvious from which one. For example, I stumbled on "STREQ" macros in cat.c code which a source of "cat" tool and can't find its declaration in the code.

So, the question is:

Is there any way to find declarations of macros, functions within a code manually or using IDE features (which I am not aware of) without googling its name to check if it an STL function or not? How do you do it usually?

Answer 1

You can run c preprocessor and examine its output for all the macro expansion, header file inclusion, conditional compilation, etc.

The compilation flag is -E in gnu c compiler.

gcc -E cat.c