[MPlayer-advusers] PATCH: FPE in demux_audio.c

[Andrew A. Gill]

--- BUG DESCRIPTION ---
There is a division by zero problem (two, actually) in
main/libmpdemux/demux_audio.c.  When playing MP3 or FLAC, it
attempts to divide by sh_audio->i_bps which is unset.

This doesn't happen when using a container, so presumably bps is
defined by the container.  For some reason, this doesn't cause
FPE on IEEE 754-conformant processors (e.g. x86, unlike DEC
Alpha).
--- BUG DESCRIPTION ---
--- RESOLUTION ---
A patch is attached.

The patch resolves the issue quite well by adding a switch-case
statement to the affected lines.  It is, however, evaluated
every time that the audio buffer is filled, so more efficient
solutions may be preferable.

Also, I suggest that the code be checked for arithmetic traps.
(if there's a test suite, I'd be happy to do it)
--- RESOLUTION ---

-- 
|Andrew A. Gill                       |I posted to Silent-Tristero and|
|<superluser at frontiernet.net>         |all I got was this stupid sig! |
|alt.tv.simpsons CBG-FAQ author       |                               |
|                          (Report all obscene mail to Le Maitre Pots)|
|Yet: <http://www.needsfoodbadly.com>                 Temporary sig: --

Yay advusers!
-------------- next part --------------
--- main/libmpdemux/demux_audio.c	2005-04-18 16:51:34.000000000 -0400
+++ main/libmpdemux/demux_audio.c	2005-07-27 20:03:00.000000000 -0400
@@ -415,7 +415,15 @@
     l = 65535;
     dp = new_demux_packet(l);
     l = stream_read(s,dp->buffer,l);
-    priv->last_pts = priv->last_pts < 0 ? 0 : priv->last_pts + l/(float)sh_audio->i_bps;
+    switch (sh_audio->i_bps)
+    {
+    case 0:
+      priv->last_pts = 0;
+      break;
+    default:
+      priv->last_pts = priv->last_pts < 0 ? 0 : priv->last_pts + l/(float)sh_audio->i_bps;
+      break;
+    }
     break;
   }
   default:
@@ -424,8 +432,16 @@
   }
 
   resize_demux_packet(dp, l);
-  ds->pts = priv->last_pts - (ds_tell_pts(demux->audio) -
-              sh_audio->a_in_buffer_len)/(float)sh_audio->i_bps;
+  switch (sh_audio->i_bps)
+  {
+  case 0:
+    ds->pts = 0;
+    break;
+  default:
+    ds->pts = priv->last_pts - (ds_tell_pts(demux->audio) -
+                sh_audio->a_in_buffer_len)/(float)sh_audio->i_bps;
+    break;
+  }
   ds_add_packet(ds, dp);
   return 1;
 }