[cpp.concat] (original) (raw)

[Example 1:

The sequence#define str(s) # s#define xstr(s) str(s) #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \ x ## s, x ## t) #define INCFILE(n) vers ## n#define glue(a, b) a ## b#define xglue(a, b) glue(a, b) #define HIGHLOW "hello" #define LOW LOW ", world"debug(1, 2); fputs(str(strncmp("abc\0d", "abc", '\4') == 0) str(: @\n), s);#include xstr(INCFILE(2).h)glue(HIGH, LOW); xglue(HIGH, LOW) results inprintf("x" "1" "= %d, x" "2" "= %s", x1, x2); fputs("strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n", s);#include "vers2.h" (after macro replacement, before file access) "hello";"hello" ", world" or, after concatenation of the character string literals,printf("x1= %d, x2= %s", x1, x2); fputs("strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n", s);#include "vers2.h" (after macro replacement, before file access) "hello";"hello, world"

Space around the # and ## preprocessing tokens in the macro definition is optional.

— _end example_]