c - Stringification of a macro value

Question

I faced a problem - I need to use a macro value both as string and as integer.

 #define RECORDS_PER_PAGE 10

 /*... */

 #define REQUEST_RECORDS 
      "SELECT Fields FROM Table WHERE Conditions" 
      " OFFSET %d * " #RECORDS_PER_PAGE 
      " LIMIT " #RECORDS_PER_PAGE ";"

 char result_buffer[RECORDS_PER_PAGE][MAX_RECORD_LEN];

 /* ...and some more uses of RECORDS_PER_PAGE, elsewhere... */

This fails with a message about "stray #", and even if it worked, I guess I'd get the macro names stringified, not the values. Of course I can feed the values to the final method ( "LIMIT %d ", page*RECORDS_PER_PAGE ) but it's neither pretty nor efficient. It's times like this when I wish the preprocessor didn't treat strings in a special way and would process their content just like normal code. For now, I cludged it with #define RECORDS_PER_PAGE_TXT "10" but understandably, I'm not happy about it.

How to get it right?

Answer 1

The xstr macro defined below will stringify after doing macro-expansion.

#define xstr(a) str(a)
#define str(a) #a

#define RECORDS_PER_PAGE 10

#define REQUEST_RECORDS 
    "SELECT Fields FROM Table WHERE Conditions" 
    " OFFSET %d * " xstr(RECORDS_PER_PAGE) 
    " LIMIT " xstr(RECORDS_PER_PAGE) ";"