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Date: Sat, 16 Aug 2008 11:38:00 -0000
From: Richard Harvey Chapman <hchapman-gcc-help@3gfp.com>
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To: gcc-help@gcc.gnu.org
Subject: Macro question regarding single quotes
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I'd like to shorten-up so redundant code in a switch statement by using 
a macro for each case. The following code illustrates the problem. In 
short, is there a way to write the PARSE(a,b) macro that will work in 
the manner shown below?


Thanks,

H.

========

#include <stdio.h>

int varAB = 1;
int varFG = 2;

#define TEST1(a,b)  printf("'%c' '%c' = %d\n", *#a, *#b, var##a##b)
#define TEST2(a,b)  printf("'%c' '%c' = %d\n", #a[0], #b[0], var##a##b)

int ParseAB(void) { return(0); }
int ParseCD(void) { return(0); }
int ParseEF(void) { return(0); }

// * not allowed in case statement
#define PARSE(a,b)   case (*#a << 8) | *#b: \
                       status = Parse##a##b();     \
                       break

// ends up being literally 'a' and 'b'
#define PARSE2(a,b)   case ('a' << 8) | 'b': \
                        status = Parse##a##b();     \
                        break

int main()
{
  int status = 0;

  TEST1(A,B);
  TEST2(F,G);

  switch (('A' << 8) | 'B')
  {
  // This is what the output of the PARSE macro should be:
  case ('A' << 8) | 'B':
    status = ParseAB();
    break;

  // This is how I'd like to use the macro.
  PARSE(C,D);
  PARSE(E,F);

  default:
    status = -1;
  }

  return(0);
}