Error pasting “”HELLO“” and “”WORLD“” does not give a valid preprocessing token

问题:

This is the faulty code

#include<stdio.h>  #define CAT_I(A, B)         A ## B #define CAT(A, B)           CAT_I(A,B)  void main (void) {         printf(CAT("HELLO","WORLD")); } 

Why it gives that error? How could I fix it?

EDIT

This is what I am trying to do

#define TAG                   "TAG" #define PRE                   CAT(CAT("<",TAG),">")   #define POS                   CAT(CAT("</",TAG),">")   #define XML      CAT(CAT(PRE,"XML SOMETHING"),POS)    

then

printf(XML);  

回答1:

The result of ## must be a single token, and "HELLO""WORLD" is not a single token. To concatenate strings, simply leave them beside each other:

printf("HELLO" "WORLD"); 

Or change your macro to remove the ##.

#define CAT(A, B) A B 

String literals are concatenated together when there are no intervening tokens between them.

文章来源: Error pasting “”HELLO“” and “”WORLD“” does not give a valid preprocessing token