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printf(" LIST.H ") where LIST.H is a macro

开发者 https://www.devze.com 2023-03-14 00:21 出处:网络
#include <stdio.h> #include<stdlib.h> #define LIST.H onus; int main () { char *p,*s; printf(\" LIST.H \");
#include <stdio.h>
#include<stdlib.h>
#define LIST.H onus;

int main ()
{
         char *p,*s;
         printf(" LIST.H ");
}

I expect LIST.H to print onus as out put. But this does not happen. upon compiling I get a warning

temp.c:3:13: warning: missing whitespace after the macro name

and the开发者_StackOverflow output is LIST.H not onus. How can I get desired thing printed by the above macro?

UPDATE

I want to have the output as onus with one space before and after the string.


Macros names cannot have . inside them. That's why you get the warning: warning: missing whitespace after the macro name, after LIST it expects a space, but it gets a . instead.

Also, when a macro name is inside a string(between "string") it is not replaced by the macro definition.

You could do this instead:

#define LISTH "onus"

// and then
  printf(LISTH);

which the preprocessor will transform to:

  printf("onus");

If you do:

#define LISTH "onus";

the preprocessor will transform it to:

 printf("onus";);

which won't compile.


Firstly, you can't use . in macro names.

Secondly, you should "expect" it to print ouns;, since you included a ; into your macro definition.

Thirdly, in order to achieve that you can use "stringization" macro-operator # with some helper macros

#define TO_STRING_(x) #x
#define TO_STRING(x) TO_STRING_(x)


#define LIST_H onus
...
printf(" " TO_STRING(LIST_H) " ");

or, better

printf(" %s ", TO_STRING(LIST_H));


#include <stdio.h>

#define LIST_H "onus"

int main()
{
    printf(LIST_H);
}


macros in strings aren't resolved, you need to layers of macro resolution to do that:

#define __STR(x) #x
#define _STR(x) __STR(x)

printf(_STR(LIST));

you also cannot have dots in macro defines last I checked, which would be what your error is about, so rather use LIST_H...

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