[mythtv-commits] Ticket #6344: Workaround lastError bug in Qt 4.5.0

[MythTV]

#6344: Workaround lastError bug in Qt 4.5.0
----------------------------------------------+-----------------------------
 Reporter:  sphery <mtdean at thirdcontact.com>  |       Owner:  ijr    
     Type:  defect                            |      Status:  new    
 Priority:  minor                             |   Milestone:  unknown
Component:  MythTV - General                  |     Version:  0.21   
 Severity:  medium                            |     Mlocked:  0      
----------------------------------------------+-----------------------------
 Qt 4.5.0 modified the Qt MySQL driver and added a bug which causes a
 lastError to sometimes be reported, even when the last statement executed
 was successfully executed.  Since Myth's DB upgrade code only checks
 lastError, non-failures are sometimes treated as failures (i.e. when
 executing the ALTER DATABASE statements that are passed to
 performActualUpdate()).

 The attached patch works around the issue by simply checking the return
 value of exec() as well as the lastError().  It only works around the
 issue in the one location where I know it exists--the DB upgrade code.
 I've checked all other locations in dbcheck.cpp that look only at
 lastError() and none will be affected by the bug (i.e. their statements
 can be executed either as prepared or non-prepared statements).  However,
 similar problems may exist in other parts of Myth.

 I've reported the bug to Qt's bug tracker and posted a patch, but it seems
 to be moderated, so a link to the bug isn't yet available.  The Qt patch
 is simple, but distros are already starting to use the buggy version of
 Qt, so the workaround may be worthwhile.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/6344>
MythTV <http://www.mythtv.org/>
MythTV