Hi,
In an XS file I have the following line of code: 
printf("%.16e", sqrt(2.0));

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I want to rewrite that line as: 
printf(MY_FORMAT, sqrt(2.0));

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I also wish to then define MY_FORMAT to "%.16e" in the Makefile.PL.

This is normally achieved by assigning an appropriate value to DEFINE in the WRITEMAKEFILE() section of the Makefile.PL - eg: 
WRITEMAKEFILE(
  .... 
  DEFINE => '-DMY_FORMAT="%.16e"',
  ....
);

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But that specific incantation fails to work - and I haven't been able to hit on the incantation that *does* work.
Update: By "not work", I mean that it either won't compile or it leads to runtime crashes (depending upon the actual incantation I've tried).
Any help would be much appreciated.

I've also spent a couple of hours trying to get this working in Inline::C. If I can get it to work in Inline::C, then I'll be able to use the incantation in the Makefile.PL that Inline::C generates.
Here's that Inline::C script: 
use strict;
use warnings;
use Config;

use Inline C => Config =>
  USING => 'ParseRegExp',
  CCFLAGSEX => '-DMY_FORMAT="%.16e"',
  BUILD_NOISY => 1,
;

use Inline C =><<'EOC';

SV * foo(void) {
  printf(MY_FORMAT, sqrt(2.0));
  printf("\n");
}

EOC

foo();

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I've tried various escapes around "%.16e" but nothing has been successful.
In C, it's pretty simple to achieve: 
C:\_32\C>type try.c
#include <stdio.h>
#include <math.h>

int main(void) {
printf(MY_FORMAT, sqrt(2.0));
return 0;
}

C:\_32\C>gcc -o try.exe try.c -DMY_FORMAT=\"%.16e\"

C:\_32\C>try
1.4142135623730951e+000
C:\_32\C>

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I'm not all that bothered if it turns out that Inline::C can't handle the construct, but I *would* like to know how to do it in the XS file via the Makefile.PL if, indeed, that's possible at all.

Cheers,
Rob

In reply to Defining an XS symbol in the Makefile.PL by syphilis

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