Timing issue with alphapulse + mythuibuttontree preventing display sometimes

[markk]

Steps to reproduce:-

• select Graphite theme (may not be relevant)
• enter Video List screen
• sometimes the list is not populated
• press the 'right' button when the list is not populated and it crashes

Strangely, the list is properly populated if I switch focus away from the frontend and back again - so perhaps some obscure interaction with the X server?

Backtrace to follow

[robertm]

updating summary to reflect the fixed segfault and remaining possible issue.

[mlord@…]

Thanks to Mark.K. for the pointer to this ticket. I can reproduce this with 100% certainty on 0.25pre.

Based on the info already here, I had a quick look at the code and immediately spotted a signed/unsigned comparison error (actually, two of them together).

This patch makes the crash go away, though I don't really understand why m_activeListID is -1 on entry there.

--- mythtv/libs/libmythui/mythuibuttontree.cpp.orig     2011-02-17 00:24:52.916137874 -0500
+++ mythtv/libs/libmythui/mythuibuttontree.cpp  2011-02-17 00:22:25.322386506 -0500
@@ -457,8 +457,13 @@
     bool doUpdate = false;
     if (right)
     {
-        if ((m_activeListID < m_visibleLists - 1) &&
-            (m_activeListID < (uint)m_buttonlists.count() - 1))
+        /*
+         * Be careful to guard against comparing negatives with uint values here.
+         * First time in with RIGHT arrow in mythvideo gives these values:
+         *      m_activeListID=-1 m_visibleLists=3 m_buttonlists.count()=3
+         */
+        if ((m_activeListID + 1 < m_visibleLists) &&
+            (m_activeListID + 1 < (uint)m_buttonlists.count()))
             m_activeListID++;
         else if (m_currentNode && m_currentNode->visibleChildCount() > 0)
         {

[mlord@…]

Patch to fix RIGHT-arrow crash on entry to mythvideo.

[stuartm]

The cause of the failure to populate the list is still a mystery, won't be solved for 0.25

[Github]

Fix segfault in MythUIButtonTree when list is empty and we attempt to navigate it. Refs #9101

Signed-off-by: Stuart Morgan <smorgan@…>

Branch: master Changeset: f3efafe2d71efcee847c3be5710eef42d49e066f

[stuartm]

I'm going to close this for now, I cannot reproduce and there isn't enough information here to debug it without reproducing.