crash opening image file

Better stack trace with debug symbols installed:
Core was generated by `./gallery-app'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0xb5b2201c in std::string::assign(std::string const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
(gdb) bt
#0 0xb5b2201c in std::string::assign(std::string const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#1 0xacebe712 in operator= (__str=..., this=0xa68cc6fc)
    at /usr/include/c++/4.9/bits/basic_string.h:555
#2 ThumbnailCachePrivate::get_cache_file_name (this=0x0, abs_original=...,
    desired=desired@entry=TN_SIZE_LARGE)
    at /build/buildd/thumbnailer-1.2+14.10.20140814/src/thumbnailcache.cpp:246
#3 0xacebec62 in ThumbnailCache::get_if_exists (this=0x7641d4, abs_path=...,
    desired_size=desired_size@entry=TN_SIZE_LARGE)
    at /build/buildd/thumbnailer-1.2+14.10.20140814/src/thumbnailcache.cpp:264
#4 0xacebff34 in Thumbnailer::get_thumbnail (this=0x490db8, filename=...,
    desired_size=TN_SIZE_LARGE, policy=policy@entry=TN_LOCAL)
    at /build/buildd/thumbnailer-1.2+14.10.20140814/src/thumbnailer.cpp:197
#5 0xacec00ae in Thumbnailer::get_thumbnail (this=<optimized out>,
    filename=..., desired_size=<optimized out>)
    at /build/buildd/thumbnailer-1.2+14.10.20140814/src/thumbnailer.cpp:201
#6 0xacf7b70e in ThumbnailGenerator::requestImage(QString const&, QSize*, QSize const&) ()
   from /usr/lib/arm-linux-gnueabihf/qt5/qml/Ubuntu/Components/libUbuntuComponents.so
#7 0xb640acfa in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Quick.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)

This backtrace does not make any sense. ThumbnailCache object exists:

#3 0xacebec62 in ThumbnailCache::get_if_exists (this=0x7641d4

but ThumbnailCachePrivate does not:

#2 ThumbnailCachePrivate::get_cache_file_name (this=0x0

I went through the code but found no code path that could possibly lead to this. The private variable is only assigned to in the constructor with new. If it fails it should throw an exception so the ThumbnailCache object is never created.

The plot thickens. Compiling with asan on ARM gives the following for downloadertest:

Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? ()
(gdb) bt
#0 0x00000000 in ?? ()
#1 0xb6b19344 in pthread_cond_init () from /usr/lib/arm-linux-gnueabihf/libasan.so.1
#2 0xb6a70e96 in xmlNewRMutex__internal_alias () at ../../threads.c:308
#3 0xb6aa7fd8 in __xmlInitializeDict () at ../../dict.c:179
#4 0xb6927092 in pthread_once () from /lib/arm-linux-gnueabihf/libpthread.so.0
#5 0xb6a710da in xmlIsMainThread__internal_alias () at ../../threads.c:803
#6 0xb6a70916 in __xmlGenericError__internal_alias () at ../../globals.c:865
#7 0xb6a28ce2 in xmlInitParser__internal_alias () at ../../parser.c:14728
#8 0xb6a38110 in xmlInitParser__internal_alias () at ../../parser.c:15297
#9 xmlReadMemory__internal_alias (buffer=0xb3a0175c "<album><coverart><large>http://dummy</large></coverart></album>", size=63, URL=0x0, encoding=0x0,
    options=257) at ../../parser.c:15293
#10 0x0005ce0a in LastFMDownloader::parseXML (this=0xbeffee80, xml=...) at ../src/lastfmdownloader.cpp:44
#11 0x0005d4ba in LastFMDownloader::download (this=0xbeffee80, artist=..., album=..., fname=...) at ../src/lastfmdownloader.cpp:75
#12 0x00056140 in Downloader_canned_Test::TestBody (this=0xb44008d0) at ../tests/download.cpp:54
#13 0x0008f2b0 in testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void> (object=0xb44008d0,
    method=&virtual testing::Test::TestBody(), location=0xa50c0 "the test body") at /usr/src/gtest/src/gtest.cc:2078
#14 0x00087bd6 in testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void> (object=0xb44008d0,
    method=&virtual testing::Test::TestBody(), location=0xa50c0 "the test body") at /usr/src/gtest/src/gtest.cc:2114
#15 0x0006628a in testing::Test::Run (this=0xb44008d0) at /usr/src/gtest/src/gtest.cc:2151
#16 0x00066d8c in testing::TestInfo::Run (this=0xb3402b90) at /usr/src/gtest/src/gtest.cc:2326
#17 0x00067632 in testing::TestCase::Run (this=0xb4a02980) at /usr/src/gtest/src/gtest.cc:2444
#18 0x00070790 in testing::internal::UnitTestImpl::RunAllTests (this=0xb3203dc0) at /usr/src/gtest/src/gtest.cc:4315
#19 0x00091034 in testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> (object=0xb3203dc0,
    method=(bool (testing::internal::UnitTestImpl::*)(testing::internal::UnitTestImpl * const)) 0x70121 <testing::internal::UnitTestImpl::RunAllTests()>,
    location=0xa74c0 "auxiliary test code (environments or event listeners)") at /usr/src/gtest/src/gtest.cc:2078
#20 0x0008969e in testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> (object=0xb3203dc0,
    method=(bool (testing::internal::UnitTestImpl::*)(testing::internal::UnitTestImpl * const)) 0x70121 <testing::internal::UnitTestImpl::RunAllTests()>,
    location=0xa74c0 "auxiliary test code (environments or event listeners)") at /usr/src/gtest/src/gtest.cc:2114
#21 0x0006e70c in testing::UnitTest::Run (this=0xd1c60 <testing::UnitTest::GetInstance()::instance>) at /usr/src/gtest/src/gtest.cc:3929
#22 0x000573ec in RUN_ALL_TESTS () at /usr/include/gtest/gtest.h:2...

On build 40 the attached image does not crash the gallery.

delete the thumbnail cache and gallery cache and it still crashes on build 40:
rm -rf ~/.cache/thumbnails
rm -rf ~/.cache/com.ubuntu.gallery-app

why are the versions of libthumbnailer different on ubuntu and ubuntu-rtm? seems the ubuntu-rtm version is older. perphaps that is why the stack trace line numbers where not making sense.

I followed your steps to the letter (except that ~/.cache/com.ubuntu.gallery-app should be ~/.cache/com.ubuntu.gallery) and got no crash.

The reason for rtm being old is that we have a silo (line 14 in the spreadsheet) which has been fully tested but QA has not signed off on it for reasons we don't know.

Since this can't be reproduced any more (or ever), lowering priority to high.

Bill, can you try with the newest image? If it does not crash any more, then just close this bug. Thanks.

It still crashes on the latest rtm-proposed image (59) on krillin.
libthumbnailer0:armhf 1.2+14.10.20140916~rtm-0ubuntu1

It's very easy to reproduce.
Load up your gallery with a bunch of photos.
Open gallery
While you see thumbnails loading (i.e. spinners everywhere), as soon as one thumbnail becomes visible click on it to open, and bang it crashes. Looks to be the same dump as the previous crashes. The issue seems to happen when you try to open a thumbnail while others are loading possibly.

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
Core was generated by `./gallery-app'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0xb5b9201c in std::string::assign(std::string const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
(gdb) bt
#0 0xb5b9201c in std::string::assign(std::string const&) ()
   from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#1 0xad914ac6 in ?? () from /usr/lib/arm-linux-gnueabihf/libthumbnailer.so.0
#2 0xad91506e in ?? () from /usr/lib/arm-linux-gnueabihf/libthumbnailer.so.0
#3 0xad9165b6 in Thumbnailer::get_thumbnail(std::string const&, ThumbnailSize, ThumbnailPolicy) () from /usr/lib/arm-linux-gnueabihf/libthumbnailer.so.0
#4 0xad916736 in Thumbnailer::get_thumbnail(std::string const&, ThumbnailSize)
    () from /usr/lib/arm-linux-gnueabihf/libthumbnailer.so.0
#5 0xacf9b466 in ThumbnailGenerator::requestImage(QString const&, QSize*, QSize const&) ()
   from /usr/lib/arm-linux-gnueabihf/qt5/qml/Ubuntu/Components/libUbuntuComponents.so
#6 0xb647acfa in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Quick.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)

attaching latest CoreDump file

With the description in comment #11, I can reproduce. But it still does not give any explanation on why this is happening. :(

I instrumented thumbnailer to print some text when it is created and called. Then I copied images to the Pictures directory and clicked around. It turns out that ThumbnailGenerator::requestImage is never called. The generated thumbnails do not appear in ~/.cache/thumbnails either (which they should, unless gallery-app is requesting large enough images).

I wrote a thread torture test for thumbnailer and ran it under helgrind for 15 minutes or so and it produced no thread errors.

Even more strangely I can't reproduce this any more. Tapping on an image while others are loading works just fine.

All of this, combined with bug #1375238, makes me suspect that there is a threading bug/buffer overrun somewhere else in the stack and it just happens to manifest itself as this bug.

The real reason for this bug has been hiding in plain sight on this page all the time. Note the backtrace above:

#5 0xacf9b466 in ThumbnailGenerator::requestImage(QString const&, QSize*, QSize const&) ()
   from /usr/lib/arm-linux-gnueabihf/qt5/qml/Ubuntu/Components/libUbuntuComponents.so

This means that the thumbnailer plugin is invoked from libUbuntuComponents.so, which is provided by ubuntu-ui-toolkit and *not* from the plugin provided by thumbnailer. And, sure enough, in modules/Ubuntu/Components/plugin/plugin.cp we find this:

    try {
        engine->addImageProvider(QLatin1String("thumbnailer"), new ThumbnailGenerator);
    } catch(std::runtime_error &e) {
        qDebug() << "Could not create thumbnailer: " << e.what();
    }

This same piece of code can also be found in plugins/Ubuntu/Thumbnailer/plugin.cpp (along with the other two generators it provides.

A quick test shows that removing the registration code from thumbnailer makes these threading bugs disappear. Apparently what happens is that if you register the same image provider into Qt twice, it gets confused and starts corrupting its own data structures.

A side effect of this fix is that when you tap on a picture in the gallery app to bring it full screen, pinch-to-zoom no longer works and there is other weirdness (sometimes the image goes fully black). (As an aside, why is gallery even using the thumbnailer for this? You need the entire image for proper zooming so why not just open it directly?)

To get this fixed we need to do the following:

- decide with UI toolkit people on where the correct place for thumbnail image provider is
- once done we need to verify if the pinching bug still happens and fix it
- land all MRs dealing with the above as one clump

>>A side effect of this fix is that when you tap on a picture in the gallery app to
>>bring it full screen, pinch-to-zoom no longer works and there is other weirdness
>>(sometimes the image goes fully black). (As an aside, why is gallery even using the thumbnailer for this?
>> You need the entire image for proper zooming so why not just open it directly?)

You are correct. Ineed the gallery-app and camera-app are both using the thumbnail when opening the picture instead of using the picture directly. This is being tracked in this bug https://bugs.launchpad.net/gallery-app/+bug/1376767 and an MR already been submitted for camera-app.

Instead of using try-catch perhaps an interrogation whether the image provider is already installed should be made. QQmlEngine provides API for it, don't know why is not used...

This provider has been in and out of UI toolkit, and yes, I agree, someone should decide where is its place.

Meanwhile I suggest all to check whether an image provider is registered before registering, and then no try-catch combination would be needed. And, Jussi, it was you who actually put that try-catch section in the toolkit ;)

How about I make a MR that rips out the provider from UI toolkit and we just try it and see if anything breaks? Or are there subtle bug sources that I as a non-qt expert am not aware of?

Jussi, we are not doing changes and see whether the solar system collapses :) You can propose an MR, then test it, build a package out of it and then check the apps around :).

If one uses the packages from the linked MR, thumbnails in the gallery app stop working and print this error:

file:///usr/share/click/preinstalled/com.ubuntu.gallery/2.9.1.1084/rc/qml/OrganicView/OrganicMediaList.qml:165:24: QML QQuickImage: Invalid image provider: image://thumbnailer//home/phablet/Pictures/com.ubuntu.camera/image20141008_085937290.jpg

Which means that it can't see the thumbnailer's qml plugin. Which is totally weird because e.g. album art works on the music app and their imports are identical (import Ubuntu.Thumbnailer 0.1). I'm totally at a loss here.

I fixed the imports in gallery-app. When using the packages combining the two linked branches, things work for me.

Bill, can you try them and verify if this fixes the crashes for you?

If we merge these branches as is then all programs that used "import Ubuntu.Components" instead of "Ubuntu.Thumbnailer" will have broken thumbnails until they fix their imports. Only few applications use thumbnailer and all others I know of have proper imports so this impact is minimal (probably zero). However I'll let someone else make the policy call.

I tested this and indeed it seems to fix the crash in the gallery and make things operate much more smoothly. I'm +1 with the approach and so is Florian.

Before we can land this, I'd suggest the following. Jussi if you or tstrehl could do this it would be good:
- [jussi/tstrehl] ask popey to see if he can grep through all of the core apps/apps in the store for the use of "image://thumbnailer" in the qml and if found make sure they are flagged to change add the import of Ubuntu.Thumbnailer.
- [jussi/tstrehl] send an email to the public phone list notifying folks of the change just to give a heads up.
- [all] lets test other apps in the image (and scopes) to make sure nothing else breaks. I can help with this part.

I have done the first two and asked for review for the ui toolkit change. Could one of you approve the gallery-app one (it has test flakiness according to Jenkins but that is unrelated to this change)?

I tested the change to gallery and it does not cause any problems without the ui-toolkit change. So I am in process of landing gallery-app (it's in it's own silo with other gallery changes). I've removed it from the test silo 10. So gallery will land first and ui-toolkit can land any time after that.

This bug was fixed in the package gallery-app - 0.0.67+14.10.20141010-0ubuntu1

---------------
gallery-app (0.0.67+14.10.20141010-0ubuntu1) 14.09; urgency=low

  [ Bill Filler ]
  * Scale the album title proportionally to the album itself, so it
    works on all devices. (LP: #1377767)

  [ Ubuntu daily release ]
  * New rebuild forced

  [ Florian Boucault ]
  * Respect EXIF orientation when showing a photo by starting to use the
    GalleryStandardImageProvider again. (LP: #1377298)

  [ Jussi Pakkanen ]
  * Fix thumbnailer import. (LP: #1368492)

  [ Ugo Riboni ]
  * Scale the album title proportionally to the album itself, so it
    works on all devices. (LP: #1377767)
 -- Ubuntu daily release <email address hidden> Fri, 10 Oct 2014 01:30:08 +0000

changing ubuntu trunk task to high to clean metrics

This bug was fixed in the package gallery-app - 0.0.67+14.10.20141010-0ubuntu1

---------------
gallery-app (0.0.67+14.10.20141010-0ubuntu1) 14.09; urgency=low

  [ Bill Filler ]
  * Scale the album title proportionally to the album itself, so it
    works on all devices. (LP: #1377767)

  [ Ubuntu daily release ]
  * New rebuild forced

  [ Florian Boucault ]
  * Respect EXIF orientation when showing a photo by starting to use the
    GalleryStandardImageProvider again. (LP: #1377298)

  [ Jussi Pakkanen ]
  * Fix thumbnailer import. (LP: #1368492)

  [ Ugo Riboni ]
  * Scale the album title proportionally to the album itself, so it
    works on all devices. (LP: #1377767)
 -- Ubuntu daily release <email address hidden> Fri, 10 Oct 2014 01:30:08 +0000

This bug was fixed in the package ubuntu-ui-toolkit - 1.1.1298+14.10.20141016.1-0ubuntu1

---------------
ubuntu-ui-toolkit (1.1.1298+14.10.20141016.1-0ubuntu1) 14.09; urgency=medium

  [ Jussi Pakkanen]
  * Remove the thumbnailer image provider here, because thumbnailer
    provides it by itself Fixes LP: #1368492

  [ Lars Uebernickel ]
  * Icon: size correctly even if no or only one dimension is given

  [ Michael Sheldon]
  * Check that orientation changes are acceptable before applying new
    orientation based on active window change. Fixes LP: #1375306

  [ Zoltán Balogh ]
  * Updated test plan executer

  [ Zeller Benjamin ]
  * RenderTimer includes EGL platform files in the rendertime header,
    which can cause problems when included after QDataStream. The
    EGL headers pull the XLib files which define the Symbol Status.
  * Preparing qmlapicheck to support out of source builds for the
    cmake migration

  [ Renato Filho ]
  * Save alarms in invalid time zone. Use invalid time zone to
    floating time alarms.

  [ Tim Peeters ]
  * Make icons from theme in showcase gallery scrollable.
    Fixes: LP: #1336279.
  * Fix width of header contents. Fixes LP: #1378261.

  [ Sebastien Bacher ]
  * Don't use simple quotes around translatable strings, xgetting
    ignore those. Fixes LP: #1378774.

  [ Zsombor Egri ]
  * Alarm update regression caused by EDS changes. Also fixes Tags
    update. Requires qtorganizer5-eds updates as well!.
    Fixes LP: #1364949.
  * Forgotten Interface declaration in objects. Fixes LP: #1378298

  [ Christian Dywan ]
  * Make dialog contents scrollable. Fixes LP: #1376763
  * Make mouseMoveSlowly work with a negative distance.
    Fixes LP: #1343334
  * Read-only text entries don't blink or visibly take focus
    Fixes LP: #1370571
  * Anchor overflow button labels to the right.
    Fixes LP: #1354812 LP: #1378247
  * Don't allow inserting a line break into readOnly text areas.
    Fixes LP: #1334344

  [ Ubuntu daily release ]
  * New rebuild forced

ubuntu-ui-toolkit (1.1.1286+14.10.20141007-0ubuntu2) UNRELEASED; urgency=medium

  [ Renato Filho ]
  * Save alarms in invalid time zone. Use invalid time zone to
    floating time alarms.

  [ Tim Peeters ]
  * Make icons from theme in showcase gallery scrollable.
    Fixes: LP: #1336279.
  * Fix width of header contents. Fixes LP: #1378261.

  [ Sebastien Bacher ]
  * Don't use simple quotes around translatable strings, xgetting
    ignore those. Fixes LP: #1378774.

  [ Zsombor Egri ]
  * Alarm update regression caused by EDS changes. Also fixes Tags
    update. Requires qtorganizer5-eds updates as well!.
    Fixes LP: #1364949.

  [ Christian Dywan ]
  * Make dialog contents scrollable. Fixes LP: #1376763
  * Make mouseMoveSlowly work with a negative distance.
    Fixes LP: #1343334
 -- Ubuntu daily release <email address hidden> Thu, 16 Oct 2014 13:01:01 +0000

This bug was fixed in the package ubuntu-ui-toolkit - 1.1.1311+15.04.20141102-0ubuntu1

---------------
ubuntu-ui-toolkit (1.1.1311+15.04.20141102-0ubuntu1) vivid; urgency=medium

  [ Zoltán Balogh ]
  [ Christian Dywan <email address hidden>
  * Explicitly use Orange in Slider and ProgressBar.
    Fixes: LP: #1372585.
  * Copy components correctly in push_to_phone.sh and make copy.sh
    more robust.
  * Make push_to_phone.sh use a temporary folder and sudo.

  [ Zsombor Egri <email address hidden>
  * ThinDivider margins rolled back to edge-to-edge. Divider colors
    adjusted with design. Fixes: LP: #1380766.

  [ Tim Peeters <email address hidden>
  * Add updated header divider to use rectangles instead of images,
    and to auto-detect its color. Fixes: LP: #1372590.
  * Add internal property to hide the header separator.
    Needed in Unity8.

  [ Leonardo Arias Fonseca <email address hidden>
  * Fixed the infinite loop when running flickable tests.
    Fixes: LP: #1384703.
  * Added an autopilot helper for expandable list items.
    Fixes: LP: #1340227.
  * The autopilot helpers to swipe to show more now get the flickable
    containers by default. Fixes: LP: #1365674.
  * Replaced the tabs for spaces in UbuntuTestCase.
   Fixes: LP: #1324469.

ubuntu-ui-toolkit (1.1.1298+14.10.20141030~rtm-0ubuntu1) 14.09; urgency=low

  [ CI bot ]
  * Resync trunk

  [ Timo Jyrinki ]
  * Modify test .desktop file (LP: #1382414) (LP: #1382414)

ubuntu-ui-toolkit (1.1.1298+14.10.20141016.1-0ubuntu1) 14.09; urgency=medium

  [ Jussi Pakkanen]
  * Remove the thumbnailer image provider here, because thumbnailer
    provides it by itself Fixes LP: #1368492

  [ Lars Uebernickel ]
  * Icon: size correctly even if no or only one dimension is given

  [ Michael Sheldon]
  * Check that orientation changes are acceptable before applying new
    orientation based on active window change. Fixes LP: #1375306

  [ Zoltán Balogh ]
  * Updated test plan executer

  [ Zeller Benjamin ]
  * RenderTimer includes EGL platform files in the rendertime header,
    which can cause problems when included after QDataStream. The
    EGL headers pull the XLib files which define the Symbol Status.
  * Preparing qmlapicheck to support out of source builds for the
    cmake migration

  [ Renato Filho ]
  * Save alarms in invalid time zone. Use invalid time zone to
    floating time alarms.

  [ Tim Peeters ]
  * Make icons from theme in showcase gallery scrollable.
    Fixes: LP: #1336279.
  * Fix width of header contents. Fixes LP: #1378261.

  [ Sebastien Bacher ]
  * Don't use simple quotes around translatable strings, xgetting
    ignore those. Fixes LP: #1378774.

  [ Zsombor Egri ]
  * Alarm update regression caused by EDS changes. Also fixes Tags
    update. Requires qtorganizer5-eds updates as well!.
    Fixes LP: #1364949.
  * Forgotten Interface declaration in objects. Fixes LP: #1378298

  [ Christian Dywan ]
  * Make dialog contents scrollable. Fixes LP: #1376763
  * Make mouseMoveSlowly work with a negative distance.
    Fixes LP: #1343334
  * Read-only text entries don't blink or visibly take focus
    Fixes LP: #1370571
  * Anchor overflow but...