commit 9d3d141c412baa5c713ad3df48f1a4d179e07b05
Author: Daniel Veillard <veillard@redhat.com>
Date:   Tue Sep 15 18:41:30 2009 +0200

    Fix a parsing problem with little data at startup
    
    * parser.c: inkscape extension loader (and possibly others) feed
      data to the parser very slowly, 0 at start, 4 bytes on first GROW
      and this broke after the fix for
      https://bugzilla.gnome.org/show_bug.cgi?id=566012
      http://git.gnome.org/cgit/libxml2/commit/?id=7e385bd4e28a0cc12b6b26ed178c620e3c3ab8d8
      leading to another bug
      https://bugzilla.redhat.com/show_bug.cgi?id=523002
      this detects the situation and GROW when needed for proper processing.

diff --git a/parser.c b/parser.c
index e415339..b41dcc3 100644
--- a/parser.c
+++ b/parser.c
@@ -10130,8 +10130,12 @@ xmlParseDocument(xmlParserCtxtPtr ctxt) {
     /*
      * Check for the XMLDecl in the Prolog.
      * do not GROW here to avoid the detected encoder to decode more
-     * than just the first line
+     * than just the first line, unless the amount of data is really
+     * too small to hold "<?xml version="1.0" encoding="foo"
      */
+    if ((ctxt->input->end - ctxt->input->cur) < 35) {
+       GROW;
+    }
     if ((CMP5(CUR_PTR, '<', '?', 'x', 'm', 'l')) && (IS_BLANK_CH(NXT(5)))) {
 
 	/*