uhh ... typo?

for( i = items, i < items; i++ )
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for( i = 0; i < items; i++ )
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Update: ... well actually it should be i = 2, since you have file and fmt.

char ** typemap in perlxs shows a couple of ways to do it.

There are two portable, non-Perl specific libraries: One is libffi. The other is ffcall (ftp server not responding as I write this).

There is a Perl interface to ffcall: FFI.

If you are using Windows, you can use Win32::API.

If you use the FFI or Win32::API Perl modules, you may not need to write any XS code of your own.

Also, I can email a copy of ffcall-1.10.tar.gz if you have trouble downloading it. Just email me at kahirsch at cpan dot org.

### try.pl ###
use warnings;

use Inline C => Config =>
    # CLEAN_AFTER_BUILD => 0,
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

void foo(FILE * fh, SV* sv, ...) {
     dXSARGS;
     int i, arg;
     printf("%s ", SvPV_nolen(ST(1)));
     for (i = 2; i < items; i++) {
          arg = SvUV(ST(i));
          printf("%d ", arg);
     }
     XSRETURN(0);
}
    
EOC

open($rd, '<', 'try.pl') or die $!;

$fmt = "foobar";

foo($rd, $fmt, 1 .. 5);
print "\n";
foo($rd, $fmt, 21 .. 32);
print "\n";
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If your function expects a variable length list of arguments of different types, the best approach would probably be to replace it by another function accepting a list of SVs, implemented using lower level functions.

Another option would be to implement the formating part in Perl, for instance:

sub FWriteF {
  my $file = shift;
  my $fmt = shift;
  my $text = sprintf($fmt, @_);
  _FRwriteF($file, $text);
     # calls C function as 
     # FWriteF($file, "%s", $text);
}
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If your function expects a variable list of arguments of the same type, sometimes it is acceptable to set a limit on the number or arguments so you can use something like this:

int
FWriteF(file, fmt, a0=0, a1=0, a2=0, a3=0,...., a10=0)
   FILE *file,
   const char *fmt
   int a0
   int a1
   ...
   int a10
CODE:
  switch (items - 2) {
    case 0:
      RETVAL = FWriteF(file, fmt);
      break;
    case 1:
      RETVAL = FWriteF(file, fmt, a1);
      break;
    case 0:
      RETVAL = FWriteF(file, fmt, a1, a2);
      break;
    ...
    case 10:
      RETVAL = FWriteF(file, fmt, a1, a2, a3, ..., a10);
      break;
  }
OUTPUT:
  RETVAL

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