C preprocessor macro generation from another macro

Question

I want to create a macro-list of macro from another macro-list of macro. I don't know how to describe this, so let me introduce an example :

#include <stdio.h>

#define     MACRO_LIST_DEFAULT              \
    MACRO(TEST1, TEST2)                     \
    MACRO(TEST3, TEST4)

#define     MACRO_LIST_MODIFIED             \
    MACRO(TEST1_MODIFIED, TEST2_MODIFIED)   \
    MACRO(TEST3_MODIFIED, TEST4_MODIFIED)

#define     MACRO_LIST_FULL                 \
    MACRO_LIST_DEFAULT                      \
    MACRO_LIST_MODIFIED

#define MACRO(VAR1, VAR2)   printf("%s:%s\n", #VAR1, #VAR2);

int main(void)
{
    MACRO_LIST_FULL
}

// OUTPUT :
// TEST1:TEST2
// TEST3:TEST4
// TEST1_MODIFIED:TEST2_MODIFIED
// TEST3_MODIFIED:TEST4_MODIFIED

This work perfectly, and it is what I want to do, but I don't want to fill the "MACRO_LIST_MODIFIED" by hand, but use the previous list "MACRO_LIST_DEFAULT"

something like that in fact :

#define MACRO_LIST_MODIFIED                 \
    MACRO_LIST_DEFAULT // And add _MODIFIED to elements.

I really don't know how to deal with this problem.

thank you in advance,

Create a new program which outputs these macro definitions for you? — Some programmer dude
– Some programmer dude, Commented Jul 2, 2015 at 12:24
The "MACRO_LIST_DEFAULT" contains ~100 items and I can't have third-party program to generate the other list. I want to keep things clearly and simple with macro tricks if that can be done. — eroween
– eroween, Commented Jul 2, 2015 at 12:31

Brian Sidebotham · Accepted Answer · 2015-07-02 12:56:07Z

1

Here you go, I assume this is what you want to achieve and I assume you're using gcc:

#include <stdio.h>

#define     MACRO_LIST( x )              \
    MACRO(TEST1 ## x , TEST2 ## x )                     \
    MACRO(TEST3 ## x , TEST4 ## x )

#define     MACRO_LIST_FULL                 \
    MACRO_LIST( )                      \
    MACRO_LIST( _MODIFIED )

#define MACRO(VAR1, VAR2)   printf("%s:%s\n", #VAR1, #VAR2);

int main(void)
{
    MACRO_LIST_FULL
}

answered Jul 2, 2015 at 12:56

Brian Sidebotham

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1 Comment

eroween Over a year ago

I was looking for a proper way to do this, this is a good one. Thank you.

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