[mythtv-commits] Ticket #9447: MacOS X - Qt binaries log spam

[MythTV]

#9447: MacOS X - Qt binaries log spam
-------------------------------------------------+-------------------------
 Reporter:  Craig Treleaven <ctreleaven@…>       |          Owner:  nigel
     Type:  Bug Report                           |         Status:
 Priority:  minor                                |  accepted
Component:  Ports - OSX                          |      Milestone:  unknown
 Severity:  medium                               |        Version:
 Keywords:                                       |  0.24-fixes
                                                 |     Resolution:
                                                 |  Ticket locked:  0
-------------------------------------------------+-------------------------

Comment (by mythtv@…):

 This issue is being caused by Qt loading its plugins from the `.osx-
 packager/build/plugins` directory due to a misconfigured plugins path, as
 returned by [[https://qt-
 project.org/doc/qt-4.8/qlibraryinfo.html|QLibraryInfo::Location(QLibraryInfo::PluginsPath)]].
 It appears to become more of an issue with later versions of Qt, as with
 4.8 at least it results in a application crash for me.

 The documentation covering [[https://qt-project.org/doc/qt-4.8/deployment-
 mac.html#qt-plugins|plugins]] as part of Deploying an Application on Mac
 OS X suggests the use of a [[https://qt-project.org/doc/qt-4.8/qt-
 conf.html|qt.conf]] file in order to adjust the plugins path to be within
 the application bundle. However, placing a `qt.conf` file within
 `<app_bundle>/Contents/Resources`, as suggested, is not picked up. The
 reason for this is that the code within
 `QLibraryInfoPrivate::findConfiguration()`, whose role is to locate and
 parse the `qt.conf` file during initialisation, contains a check for
 whether the `QCoreApplication` has been initialised:

 {{{
     if (!QFile::exists(qtconfig) && QCoreApplication::instance()) {
         ...
     }
 }}}

 and the `iso8859_codecs` global static array of [[https://qt-
 project.org/doc/qt-4.8/qtextcodec.html|QTextCodec]] objects, which are
 implemented as plugins, in `mythtv/libs/libmythtv/mpeg/dvbdescriptors.cpp`
 is initialised before reaching `main()` and consequently before the
 `QApplication` instance has been initialised.

 The attached patches move the `iso8859_codecs` array into the
 `decode_text()` function within
 `mythtv/libs/libmythtv/mpeg/dvbdescriptors.cpp`, as this appears to be the
 only function that requires the array and through relocating its
 initialisation is deferred until the function is called, which will be
 after the `QApplication` has been initialised. This change allows the
 `QLibraryInfoPrivate::findConfiguration()` function to be called later and
 consequently it behaves as expected and a [[https://qt-
 project.org/doc/qt-4.8/qt-conf.html|qt.conf]] file placed within
 `<app_bundle>/Contents/Resources` will be correctly detected. The `osx-
 packager.pl` script is then modified to copy the plugins from `.osx-
 packager/build/plugins` to `<app_bundle>/Contents/Resources` and to
 rewrite the embedded dynamic library references to refer to the copies of
 Qt libraries within the bundle, and an empty
 `<app_bundle>/Contents/Resources/qt.conf` file is generated to indicate to
 Qt that it should not be using the installation prefix path it was
 compiled with.

 The loading of the plugins from `.osx-packager/build/plugins` and
 consequently the processing of the embedded dynamic library references to
 the version of Qt libraries within `.osx-packager/build/lib` when combined
 with the rewritten references to Qt libraries within the packaged
 executables within the application bundle are the root cause of `"loading
 two sets of Qt binaries"` errors. Copying the plugins into the application
 bundle and rewriting their dynamic library references and then actually
 loading them is what ensures only one set of Qt binaries are ever loaded.

-- 
Ticket URL: <http://code.mythtv.org/trac/ticket/9447#comment:6>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center