Re: texinfo-5.9.90 pretest available

[Ken Brown]

On 2/27/2015 9:39 AM, Eli Zaretskii wrote:
> > Date: Fri, 27 Feb 2015 13:43:48 +0000
> > From: Gavin Smith <address@hidden>
> > Cc: Eli Zaretskii <address@hidden>, Karl Berry <address@hidden>, Texinfo 
> > <address@hidden>
> >
> > On 27 February 2015 at 13:13, Ken Brown <address@hidden> wrote:
> > > No, it turns out that it has to do with buffered I/O.  See the thread
> > > starting here:
> > >
> > >    https://cygwin.com/ml/cygwin/2015-02/msg00887.html
> > >
> > > Replacing the fseek in line 841 by another call to freopen fixes the
> > > problem.  I don't know if that's the best solution.
> >
> > The setvbuf solution might work - I'm not sure if the buffering
> > property of the FILE stream will be inherited by the subprocess, or
> > just the file descriptor (i.e. what "open" would return instead of
> > what "fopen" would return).
>
> Isn't FILE buffering implemented in libc, i.e. in user-space private
> to the application?  If it is, then the buffer is not inherited.
>
> The buffering that the Cygwin maintainer alluded to is the one below
> stdio, in 'read' and its ilk.  That one emulates the OS buffering, and
> is indeed inherited together with the file descriptor.
>
> > The main thing would be if we are reading from an uncompressed file
> > in install-info (the parent process) - buffering should be turned
> > back on in that case. Another solution would be to read the first
> > few bytes of the file using "open", "read" and "lseek", and make a
> > FILE stream afterwards from the file descriptor; this would avoid
> > any buffering done by the high-level FILE streams.
>
> I'm actually asking myself why do we redirect stdin to the file before
> reading it, instead of using 'fopen' to read the few first bytes, and
> then, only if it is compressed, redirect stdin to it and call 'popen'.
> Wouldn't that work around the problem?

Like this?

Index: install-info/install-info.c
===================================================================
--- install-info/install-info.c (revision 6157)
+++ install-info/install-info.c (working copy)
@@ -700,35 +700,35 @@
     opened_filename = &local_opened_filename;

   *opened_filename = filename;
-  f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+  f = fopen (*opened_filename, FOPEN_RBIN);
   if (!f)
     {
       *opened_filename = concat (filename, ".gz", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
   if (!f)
     {
       free (*opened_filename);
       *opened_filename = concat (filename, ".xz", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
   if (!f)
     {
       free (*opened_filename);
       *opened_filename = concat (filename, ".bz2", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
   if (!f)
     {
       free (*opened_filename);
       *opened_filename = concat (filename, ".lz", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
   if (!f)
     {
      free (*opened_filename);
      *opened_filename = concat (filename, ".lzma", "");
-     f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+     f = fopen (*opened_filename, FOPEN_RBIN);
     }
 #ifdef __MSDOS__
   if (!f)
@@ -735,13 +735,13 @@
     {
       free (*opened_filename);
       *opened_filename = concat (filename, ".igz", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
   if (!f)
     {
       free (*opened_filename);
       *opened_filename = concat (filename, ".inz", "");
-      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      f = fopen (*opened_filename, FOPEN_RBIN);
     }
 #endif /* __MSDOS__ */
   if (!f)
@@ -757,7 +757,7 @@
           (*create_callback) (filename);

           /* And try opening it again.  */
-          f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+          f = fopen (*opened_filename, FOPEN_RBIN);
           if (!f)
             return 0;
         }
@@ -843,6 +843,9 @@

   if (*compression_program)
     { /* It's compressed, so open a pipe.  */
+      f = freopen (*opened_filename, FOPEN_RBIN, stdin);
+      if (!f)
+       return 0;
       char *command = concat (*compression_program, " -d", "");
       f = popen (command, "r");
       if (! f)