syphilis has asked for the wisdom of the Perl Monks concerning the following question:

Hi,
Well ... I think it's a C question ... and therefore ot.

On win32 I run the following Inline::C script: 
use warnings;

use Inline C => <<'EOC';

void foo() {
     printf("HELLO");
}

EOC

for(1..3) {
   foo();
   print "\n";
}

[download]
This outputs exactly what I expect and want - namely: 
C:\_32\pscrpt\inline>perl try.pl
HELLO
HELLO
HELLO

C:\_32\pscrpt\inline>

[download]
But on my linux (mandrake-9.1) box the same script produces (transcribed): 
[rob@localhost inline]$ perl try.pl



HELLOHELLOHELLO[rob@localhost inline]$

[download]
I'm wanting to see essentially the same as appears on the win32 box - that is, I want to see the same as would be output by print "HELLO\nHELLO\nHELLO\n";.
How do I get that output on linux by modifying only the foo (Inline::C) function ? Is it possible ?

Cheers,
Rob

Replies are listed 'Best First'.
Re: [OT]: Flushing XS buffers portably
by derby (Abbot) on Aug 31, 2007 at 13:01 UTC

    Check out perlapio ... you shouldn't be using stdio for printing but perl's IO abstraction interface: 

    use warnings;

use Inline C => <<'EOC';

void foo() {
  PerlIO_printf(PerlIO_stdout(),"HELLO");
}

EOC

for(1..3) {
   foo();
   print "\n";
}

    [download]

    -derby
[reply]
[d/l]
      Dammit, derby, you found the escape clause :-)

      In real life, foo calls a third party C library function that does use stdio for printing ... something like: 
      use Inline C => <<'EOC';
#include <mpfr.h>

void foo(mpfr_t * x) {
  mpfr_out_str(*x, .......);
}

EOC

      [download]
      The Inline::C script that I presented was the closest thing I could think of that would actually depict the problem generically ... but, as I can now see, I stuffed up.

      So ... although your response answers the question I asked, it doesn't really address the question I was hoping to be answered ... my fault, not yours.

      I guess I'm really after a way of flushing the stdio printf buffer - sort of an stdio way of doing $| = 1; (if such exists).

      Btw, I had long wondered about the advantages of using the PerlIO_* routines as recommended in perldoc perlclib (and other places). Your reply provides an excellent demonstration of those "advantages". Thank you.

      Cheers,
      Rob
[reply]
[d/l]
[select]
        I guess I'm really after a way of flushing the stdio printf buffer - sort of an stdio way of doing $| = 1; (if such exists).

        Have you tried fflush(3)?

        (It's not autoflushing, though; you have to call it whenever you want to have the buffers flushed...)

[reply]
[d/l]

Back to Seekers of Perl Wisdom