Optimize persistent data

[sorokin]

No description provided.

[sorokin]

@sledgehammer999 ping

Could you review this pull request? I think it should improve situation in #646, #1203, #1235, #1542, #1592 and, probably, #674.

[sledgehammer999]

-I haven't forgotten this-

[sorokin]

qbittorrent constantly crashes at startup. Possibly related to this pull request:

$ ASAN_SYMBOLIZER_PATH=/usr/bin/llvm-symbolizer-3.4 ASAN_OPTIONS=symbolize=1 ./qbittorrent

ASAN:SIGSEGV

==9117== ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x00000070c82b sp 0x7fff5e903060 bp 0x7fff5e903160 T0)
AddressSanitizer can not provide additional info.
recalculate_auto_managed_torrents
#0 0x70c82a in QHashData::firstNode() /usr/include/qt4/QtCore/qhash.h:184
#1 0x70c82a in QHash<QString, QVariant>::constBegin() const /usr/include/qt4/QtCore/qhash.h:466
#2 0x70c82a in TorrentPersistentData::hasPerTorrentRatioLimit() /home/ivan/d/qbittorrent/src/torrentpersistentdata.cpp:238
#3 0x5d5ebe in QBtSession::updateRatioTimer() /home/ivan/d/qbittorrent/src/qtlibtorrent/qbtsession.cpp:2019
#4 0x5f4802 in QBtSession::configureSession() /home/ivan/d/qbittorrent/src/qtlibtorrent/qbtsession.cpp:560
#5 0x605d86 in QBtSession::QBtSession() /home/ivan/d/qbittorrent/src/qtlibtorrent/qbtsession.cpp:159
#6 0x60619f in QBtSession::instance() /home/ivan/d/qbittorrent/src/qtlibtorrent/qbtsession.cpp:2981
#7 0x4f44e9 in MainWindow::MainWindow(QWidget*, QStringList const&) /home/ivan/d/qbittorrent/src/mainwindow.cpp:164
#8 0x4e1d89 in main /home/ivan/d/qbittorrent/src/main.cpp:385
#9 0x7ff136139ec4 (/lib/x86_64-linux-gnu/libc.so.6+0x21ec4)
#10 0x4ad918 in _start (/home/ivan/d/qbittorrent-build/qbittorrent+0x4ad918)
SUMMARY: AddressSanitizer: SEGV /usr/include/qt4/QtCore/qhash.h:184 QHashData::firstNode()
==9117== ABORTING

[sledgehammer999]

Does the crash happen with this request or not? -sorry I didn't understand what you mean-

[sorokin]

I worked for weeks, but now I got this crash (100% reproducible). It looks like TorrentPersistentData is not initialized. But it should be initialized by the time we call QBtSession::instance() in mainwindow.cpp:164.

[sledgehammer999]

I just had a look. I don't understand how the singleton is actually initialized with this, you probably use C++ in a way that I don't know yet. (hint I am a hobbyist).
I would prefer the singleton method used in qbtsession instead for construction/decontruction of the object. It is far easier understandable.

[sorokin]

Probably miscompilation. After rebuild everything works ok.

[sorokin]

I would prefer the singleton method used in qbtsession instead for construction/decontruction of the object. It is far easier understandable.

The problem with singletons arises when one singleton accesses other in its constructor/destructor.
It is difficult to predict lifetime interaction of different singletons. Thing got worse if you conditionally accesses singleton, in that case relative lifetimes may depends on config options.

In case with PersistentData I want to assert that nobody writes it after it is saved to disk.

[sorokin]

Also I think you don't want to leave ticking timers after QApplication is terminated.

[sledgehammer999]

And I managed to break the mergability of this. @sorokin can you rebase?

[sorokin]

@sledgehammer999 done

[sledgehammer999]

@sorokin This is still unmergable. I was just going to fire up qtcreator and work out the merge conflicts. Thankfully I saw your notification first but as I said github says it has merge conflicts.

[sledgehammer999]

Thanks for the code. (I manually fixed the conflicts).