From: sos AT prospect DOT com DOT ru (Sergey Okhapkin)
Subject: RE: Question
8 Apr 1998 23:29:43 -0700
Message-ID: <01BD63A1.EC97AE90.cygnus.cygwin32.developers@SOMESHIT>
To: "'Ian Lance Taylor'" <ian AT cygnus DOT com>
Cc: "cygwin32-developers AT cygnus DOT com" <cygwin32-developers AT cygnus DOT com>

Ian Lance Taylor wrote:
>    but no __CYGWIN32__ case (mingw32?). I'm not sure that gcc will work
>    properly if cpp will terminate due to some error (spawned ΣΣ1 will 
inherit
>    last_pipe_input and will never receive EOF!). The compilation will 
just
>    hangs...

Sorry, it was a wrong example.

>
> Can you describe the potential error more fully?
>

Look at pexecute.c (lines starting with 350):

  /* If this isn't the last process, make a pipe for its output,
     and record it as waiting to be the input to the next process.  */
  if (! (flags & PEXECUTE_LAST))
    {
      if (_pipe (pdes, 256, O_BINARY) < 0)
	{
	  *errmsg_fmt = "pipe";
	  *errmsg_arg = NULL;
	  return -1;
	}
      output_desc = pdes[WRITE_PORT];
      last_pipe_input = pdes[READ_PORT];
    }
  else
    {
      /* Last process.  */
      output_desc = STDOUT_FILE_NO;
      last_pipe_input = STDIN_FILE_NO;
    }

  if (input_desc != STDIN_FILE_NO)
    {
      org_stdin = dup (STDIN_FILE_NO);
      dup2 (input_desc, STDIN_FILE_NO);
      close (input_desc);
    }

  if (output_desc != STDOUT_FILE_NO)
    {
      org_stdout = dup (STDOUT_FILE_NO);
      dup2 (output_desc, STDOUT_FILE_NO);
      close (output_desc);
    }

  pid = (flags & PEXECUTE_SEARCH ? _spawnvp : _spawnv)
    (_P_NOWAIT, program, fix_argv(argv));

Cpp (as a first task in a pipeline) will be started with stdout redirected 
to a pipe and with inheritted pipe's read end (in 
last_pipe_input=pdes[READ_PORT])! If cc1 will terminate _before_ cpp 
termination (due to fatal syntax error), cpp will hang in a write to 
stdout.

--
Sergey Okhapkin, http://www.lexa.ru/sos
Moscow, Russia.