[Haskell-cafe] Posix IO & Unicode lookup exception

[Lee Pike]

Hi,

I wanted to see if anyone had an idea about why the following program
results in an exception.  The issue seems to be related to stdin to a
POSIX file descriptors for a subprocess, and GHC's Unicode encoding
lookup.  I've tried to make the program as simple as possible to make
the issue obvious.

Consider:

> module Pipe where
>
> import System.Process
> import System.IO
> import System.Posix.IO
>
> main = sequence_ $ replicate 100000 f
>
> f = do
>   (Just hin, _, _, prc) <-
>     createProcess (shell "./pipe_c.out") { std_in = CreatePipe
>                                          , std_out = UseHandle stdout
>                                          , std_err = UseHandle stderr}
>
>   pin <- handleToFd hin
>   _   <- fdWrite pin ("h\n")
>   closeFd pin
>   waitForProcess prc

and a trivial C program to read in the data (but doing nothing with it):

---------------------------------------
#include <stdio.h>

#define SIZE 10

int main(void) {
  char in[SIZE];

  if(fgets(in, SIZE , stdin) != NULL);

  return 0;
}
----------------------------------------

and executing

> gcc -Wall -o pipe_c.out pipe_c.c
> ghci Pipe.hs
> main
  ...
*** Exception: malloc: resource exhausted (out of memory)
iconvOpen ("UTF-8","UTF-8"): resource exhausted (Cannot allocate memory)

My best guess is that the GHC is calling iconv_open()
<http://www.kernel.org/doc/man-pages/online/pages/man3/iconv_open.3.html>,
but not making a subsequent call to iconv_close()
<http://www.kernel.org/doc/man-pages/online/pages/man3/iconv_close.3.html>.
 (Actually, my best guess is I'm making a silly mistake, but I'm
having trouble seeing it. :) )

I am running 2.6.35-28-generic (Ubuntu) and GHC 7.0.2, but I've
observed the same issues with GHC 6.12.3.

Lee