bug#55737: [PATCH] 28.1; Values of `read-process-output-max' above 64k not taken into account on GNU/Linux

["Frédéric Giquel via Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Le mardi 31 mai 2022 à 15:00 +0300, Eli Zaretskii a écrit :
> > Date: Tue, 31 May 2022 13:09:38 +0200
> > From:  Frédéric Giquel via "Bug reports for GNU Emacs,
> >  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> > 
> > +#if defined(GNU_LINUX) && defined(F_SETPIPE_SZ)
> > +  fcntl (inchannel, F_SETPIPE_SZ, read_process_output_max);
> > +#endif
> 
> Shouldn't this be done only for pipe connections to the subprocess?

You're right. Setting pipe size is useless for pty connection.
Here is the new patch.

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diff --git a/src/process.c b/src/process.c
index 8b587aaa4e..eae7b26eb3 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2132,6 +2132,10 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
       inchannel = p->open_fd[READ_FROM_SUBPROCESS];
       forkout = p->open_fd[SUBPROCESS_STDOUT];
 
+#if defined(GNU_LINUX) && defined(F_SETPIPE_SZ)
+      fcntl (inchannel, F_SETPIPE_SZ, read_process_output_max);
+#endif
+
       if (!NILP (p->stderrproc))
 	{
 	  struct Lisp_Process *pp = XPROCESS (p->stderrproc);
@@ -8571,7 +8575,10 @@ syms_of_process (void)
   DEFVAR_INT ("read-process-output-max", read_process_output_max,
 	      doc: /* Maximum number of bytes to read from subprocess in a single chunk.
 Enlarge the value only if the subprocess generates very large (megabytes)
-amounts of data in one go.  */);
+amounts of data in one go.
+
+On GNU/Linux system, the value should not exceed
+`/proc/sys/fs/pipe-max-size'. See pipe(7) manpage for details. */);
   read_process_output_max = 4096;
 
   DEFSYM (Qinternal_default_interrupt_process,