问题

Background

I have a project where I have two separate products with near-identical macro names, for which I would like to create a macro-like-function to retrieve the values of the macros quickly. I have written a getTranslation macro-function to take the literal text provided to the "function", which should be treated as a string and a string prefix (shown below).

Question

How can I accomplish this operation of taking the arguments supplied to the macro, concatenating them together (with an underscore in the middle), and treating that result as a preprocessor macro instead of a string?

Code Listing

/*******************************************************************************
 * coconut.h
 ******************************************************************************/
#define COCONUT         (PRODUCT_COCONUT)
#define COCONUT_FX_REGISTER (100)
#define COCONUT_BASE_REGISTER   (101)

/*******************************************************************************
 * pineapple.h
 ******************************************************************************/
#define PINEAPPLE       (PRODUCT_PINEAPPLE)
#define PINEAPPLE_FX_REGISTER   (200)
#define PINEAPPLE_BASE_REGISTER (201)

/*******************************************************************************
 * test.c.
 ******************************************************************************/
#include <stdio.h>
#include "translation.h"
#include "coconut.h"

int main(void) {

    int i = getTranslation(FX_REGISTER, COCONUT);
    printf("Translation:%d.\n", i);

    return 0;
}

/*******************************************************************************
 * translation.h
 ******************************************************************************/
#define FX_REGISTER     (0)
#define BASE_REGISTER       (1)

#define getTranslationInternal(x, y)    #y "_" #x
#define getTranslation(x, y)        getTranslationInternal(x, y)

enum Products {
    PRODUCT_COCONUT = 0,
    PRODUCT_PINEAPPLE,
    PRODUCT_MAX,
    PRODUCT_INVALID = (-1)
};

Compiler Warnings

test.c: In function ‘main’:
test.c:10:45: warning: initialization makes integer from pointer without a cast [-Wint-conversion]
  int i = getTranslation(FX_REGISTER, COCONUT);
                                             ^
translation.h:7:39: note: in definition of macro ‘getTranslationInternal’
 #define getTranslationInternal(x, y) #y "_" #x
                                       ^
test.c:10:10: note: in expansion of macro ‘getTranslation’
  int i = getTranslation(FX_REGISTER, COCONUT);

Sample Run

Translation:4195812.

回答1:

#define getTranslationInternal(x, y)    y ## _ ## x

worked for me on clang, if you drop parentheses around the macro definitions.

来源：https://stackoverflow.com/questions/47442197/macro-function-to-generate-macro-with-prefix-avoid-stringification

标签

gcc

c-preprocessor

Macro-function to generate macro with prefix (avoid stringification)