Pre-processor: Expand a macro only once-CodePudding

Is it possible to have a macro expanded only once? In the following example, MYCONCAT is expanded to func_1(10). I want it to expand to func_BAR(10).

#define BAR 1  // included from a file I cannot change
#define FOO BAR

#define MYCONCAT2(c) func_ ## c
#define MYCONCAT(c, x) MYCONCAT2(c)(x)

MYCONCAT(FOO, 10) // is 'func_1(10)', but I want it to be 'func_BAR(10)'

CodePudding user response：

Is it possible to have a macro expanded only once?

No, it is not possible to partially expand a macro.

CodePudding user response：

Include the file that defines BAR only after the last place where MYCONCAT is used (with something that expands to BAR) instead of before it.

CodePudding user response：

Simply change #define BAR to #define _BAR and and remove the _ from func.

#define BAR 1  // included from a file I cannot change
#define FOO _BAR

#define MYCONCAT2(c) func ## c
#define MYCONCAT(c, x) MYCONCAT2(c)(x)

MYCONCAT(FOO, 10) // 'func_BAR(10)'