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From: ehj@mordor.ARPA (Eric H Jensen)
Newsgroups: net.emacs
Subject: Re: Inferior process violates gnuemacs 1st ammendment?
Message-ID: <14636@mordor.ARPA>
Date: Thu, 14-Aug-86 14:57:05 EDT
Article-I.D.: mordor.14636
Posted: Thu Aug 14 14:57:05 1986
Date-Received: Thu, 14-Aug-86 21:53:27 EDT
References: <1508@mcc-pp.UUCP>
Reply-To: ehj@mordor.UUCP (Eric H Jensen)
Organization: S-1 Project, LLNL
Lines: 99
Keywords: hot-shots, pipes, send-region, @$**&!

In article <1508@mcc-pp.UUCP> tiemann@mcc-pp.UUCP (Michael Tiemann) writes:
>On our SUN-3 about the 4th "ESC-4" the error message "writing to process:
>operation would block, cat" pops up. If we continue to type "ESC-$",
>the error sometimes comes up, and sometimes does not. On our VAX
>11/750 "running" (walking) BDS 4.2, there is no error message, but the
>gnuemacs shows up as Idle in ps -ux. (A few ^G's wake it into
>abortion-land).

I believe I had a similar problem to yours (GNUemacs 17.49).  The
cause is that emacs does an ioctl instructing unix that writes to the
pipe should not block (which, I believe, is for most purposes is the
right thing).  After thinking about it and consulting with our local
unix guru I came up with the following changes (hope this helps):


*** process.c.orig	Thu May 29 17:04:36 1986
--- process.c	Wed Jun  4 14:15:20 1986
***************
*** 166,171 ****
--- 166,174 ----
     Always -1 on systems that support FIONREAD.  */
  
  int proc_buffered_char[MAXDESC];
+ 
+ Lisp_Object Vwait_no_block;
+ 
  
  #ifdef HAVE_PTYS
  
***************
*** 1201,1206 ****
--- 1204,1217 ----
  {
    /* Don't use register vars; longjmp can lose them.  */
    int rv;
+   int fd;
+ 
+ #ifdef HAVE_TIMEVAL
+   struct timeval sd;
+   int usec;
+   int sv;
+ #endif /* HAVE_TIMEVAL */
+ 
    unsigned char *procname = XSTRING (XPROCESS (proc)->name)->data;
  
    if ((XFASTINT (XPROCESS (proc)->flags) & PROC_STATUS) != RUNNING)
***************
*** 1211,1217 ****
    if (!setjmp (send_process_frame))
      while (len > 0)
        {
! 	rv = write (XFASTINT (XPROCESS (proc)->outfd), buf, len);
  	if (rv < 0)
  	  break;
  	buf += rv;
--- 1222,1239 ----
    if (!setjmp (send_process_frame))
      while (len > 0)
        {
! 	fd = XFASTINT (XPROCESS (proc)->outfd);
! 
! #ifdef HAVE_TIMEVAL
! 	if (XTYPE (Vwait_no_block) == Lisp_Int)
! 	  sd.tv_usec = XUINT (Vwait_no_block);
! 	else sd.tv_usec = 0;
! 	sd.tv_sec = 0;
! 	usec = 1 << fd;
! 	sv = select (fd + 1, 0,&usec, 0, &sd);
! #endif /* HAVE_TIMEVAL */
! 
! 	rv = write (fd, buf, len);
  	if (rv < 0)
  	  break;
  	buf += rv;
***************
*** 1694,1699 ****
--- 1716,1729 ----
    staticpro (&Qprocessp);
  
    staticpro (&Vprocess_alist);
+ 
+   DefLispVar ("wait-no-block", &Vwait_no_block,
+     "*If integer, unsigned value indicates number of microseconds \n\
+ for select to wait before writing to a subprocess. This mechanism \n\
+ is provided because Emacs refuses to block on writes to subprocesses.\n\
+ A non-integer value is equivalent to 0. The default value is 50000.");
+ 
+   Vwait_no_block = XFASTINT(50000);
  
    DefBoolVar ("delete-exited-processes", &delete_exited_processes,
      "*Non-nil means delete processes immediately when they exit.\n\




-- 
eric h. jensen        (S1 Project @ Lawrence Livermore National Laboratory)
Phone: (415) 423-0229 USMail: LLNL, P.O. Box 5503, L-276, Livermore, Ca., 94550
ARPA:  ehj@angband    UUCP:   ...!decvax!decwrl!mordor!angband!ehj