From bug-octave-request at bevo dot che dot wisc dot edu Mon Nov  4 15:56:04 2002
Subject: Re: sprintf prints at most 99 characters
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Dirk Eddelbuettel <edd at debian dot org>
Cc: Mirek Kwasniak <mirek at zind dot ikem dot pwr dot wroc dot pl>, bug-octave@bevo.che.wisc.edu
Date: Mon, 4 Nov 2002 15:55:51 -0600

On  3-Nov-2002, Dirk Eddelbuettel <edd at debian dot org> wrote:

| On Sun, Nov 03, 2002 at 06:49:03PM +0100, Mirek Kwasniak wrote:
| > On Sun, Nov 03, 2002 at 09:31:54AM -0800, Joseph P. Skudlarek wrote:
| > > The problem also does NOT show up 
| > > in Octave 2.1.39 compiled with gcc 2.95.2
| > 
| > .. but gcc 3.0.4 and 3.2.1 (on Debian 386) suffer from this effect :(
| 
| Might be worthwhile emailing the respective g++ maintainer (team) with a
| heads, preferably with a self-contained C++ example exibiting the same
| problem.... Volunteers?

The libc manual says that the behavior of snprintf has changed.  I
think the following patch should fix the problem.  Note that none of
this code is used if you have ostream::vform, which is available with
older versions of libstdc++.

I'm not sure of the best way to handle the case when we are using a
system that does not have ostream::vform and have old snprintf
semantics.  I guess we could use an autoconf macro.  A quick search
shows that there are a few other people with the same problem.  Maybe
a winner will emerge and we can just go with that.

jwe


2002-11-04  John W. Eaton  <jwe at bevo dot che dot wisc dot edu>

	* cutils.c (octave_vsnprintf): Handle C99 snprintf semantics.


Index: cutils.c
===================================================================
RCS file: /usr/local/cvsroot/octave/src/cutils.c,v
retrieving revision 1.11
diff -u -r1.11 cutils.c
--- cutils.c	24 Oct 2002 21:49:45 -0000	1.11
+++ cutils.c	4 Nov 2002 21:39:04 -0000
 at @ -122,6 +122,10 @@
 // We manage storage.  User should not free it, and its contents are
 // only valid until next call to vsnprintf.
 
+#if defined __GNUC__ && __GNUC__ >= 3
+#define HAVE_C99_VSNPRINTF 1
+#endif
+
 char *
 octave_vsnprintf (const char *fmt, va_list args)
 {
 at @ -130,21 +134,47 @@
 
   static char *buf = 0;
 
+  int nchars;
+
   if (! buf)
     buf = malloc (size);
 
+#if defined (HAVE_C99_VSNPRINTF)
+
+  nchars = vsnprintf (buf, size, fmt, args);
+
+  if (nchars >= size)
+    {
+      size = nchars + 1;
+      buf = realloc (buf, size);
+
+      if (buf)
+	vsnprintf (buf, size, fmt, args);
+
+      return buf;
+    }
+
+#else
+
   while (1)
     {
-      int nchars = vsnprintf (buf, size, fmt, args);
+      nchars = vsnprintf (buf, size, fmt, args);
 
       if (nchars > -1)
 	return buf;
       else
 	{
 	  size *= 2;
+
 	  buf = realloc (buf, size);
+
+	  if (! buf)
+	    return 0;
 	}
     }
+
+#endif
+
 #else
   return 0;
 #endif



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