Printing name and value of a macro

Question

I have a C program with a lot of optimizations that can be enabled or disabled with #defines. When I run my program, I would like to know what macros have been

Answer 1

Writing a MACRO that expands to another MACRO would require the preprocessor to run twice on it.
That is not done.

You could write a simple file,

// File check-defines.c
int printCompileTimeDefines()
{
#ifdef DEF1
  printf ("defined : DEF1\n");
#else // DEF1
  printf ("undefined: DEF1\n");
#endif // DEF1
// and so on...
}

Use the same Compile Time define lines on this file as with the other files.
Call the function sometime at the start.

If you have the #DEFINE lines inside a source file rather than the Makefile,
Move them to another Header file and include that header across all source files,
including this check-defines.c.

Hopefully, you have the same set of defines allowed across all your source files.
Otherwise, it would be prudent to recheck the strategy of your defines.

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To automate generation of this function,
you could use the M4 macro language (or even an AWK script actually).
M4 becomes your pre-pre-processor.