Bug#375967: Proposed patch for better error reporting on debian bug #375967 against fam

[Giuseppe Sacco]

Hi Anton Ivanov and Chuan-kai Lin,
I read the stacktrace and I saw, if I am not wrong, that the method
NetConnection::mprint(char * format, ...) is called with format equals
to NULL. According to the same stacktrace, the invoker is
ClientConnection::send_event(), but in this code the argument passed to
mprint() is a string constant and cannot be NULL, beside compiler
errors.

I propose a patch that fixes a minor error in the mprint code and add an
assert(format!=NULL), so that we may catch error earlier.

I only tried to compile the package, but I cannot test it in the right
way, so you are free to build and test it, and eventually give me a
feedback.

Thanks,
Giuseppe

--- a/src/NetConnection.c++	2003-01-18 15:18:12.000000000 +0100
+++ b/src/NetConnection.c++	2006-12-03 16:18:42.000000000 +0100
@@ -208,6 +208,16 @@
     if (fd < 0)
 	return;				// if closed, do nothing.
 
+    /*
+     * According to bug http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=375967
+     * this method is called with format=NULL from ClientConnection::send_event .
+     * But looking at the code in ClientConnection, format cannot be NULL.
+     * This assert verify this fact and will eventually show a compiler bug.
+     *
+     * Giuseppe Sacco, 20061203
+     */
+    assert(format != NULL);
+
     va_list args;
     va_start(args, format);
 
@@ -217,7 +227,18 @@
         msg->msg + 4, MAXMSGSIZE + 1, format, args) + 1;
     va_end(args);
 
+    /*
+     * Changed from 
     if (len <= 0 || len == MAXMSGSIZE+1) {
+     * to
+    if (len <= 0 || len > MAXMSGSIZE) {
+     * because the vsnprint return the size it would have required
+     * to store the complete string; this size may be greather than
+     * just MAXMSGSIZE+1
+     *
+     * Giuseppe Sacco, 20061203
+     */
+    if (len <= 0 || len > MAXMSGSIZE) {
         Log::error("tried to write a message that was too big");
         assert(0);
         // protocol botch.  Don't send the message.

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