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MailboxNameComparator: implement "less than", not "less or equal"

Jan Kundrát requested to merge work/mailbox-compare into master

This comparator is used for "natural order" sorting of mailboxes. The usual way of sorting is via a functor which satisfies the Compare C++ named requirement, which is effectively a "less than" operation. This code implemented a less-than-or-equal, which means that it was not usable for std::sort which would segfault:

 0x00007ffff354a35d in __dynamic_cast () from /nix/store/b0p7nvkwxr65q016zsqicrd4bcg5bv1s-gcc-10.3.0-lib/lib/libstdc++.so.6
 (gdb) bt
 #0  0x00007ffff354a35d in __dynamic_cast () from /nix/store/b0p7nvkwxr65q016zsqicrd4bcg5bv1s-gcc-10.3.0-lib/lib/libstdc++.so.6
 #1  0x00000000005d316c in (anonymous namespace)::MailboxNameComparator (a=0x520041004d005c, b=0x12ac740) at /home/jkt/work/prog/trojita/src/Imap/Model/Model.cpp:74
 #2  0x00000000005e1d46 in __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)>::operator()<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator> (__it2=..., __it1=..., this=<synthetic pointer>) at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1909
 #3  std::__unguarded_partition<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> > (__comp=..., __pivot=..., __last=..., __first=...)
     at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1909
 #4  std::__unguarded_partition_pivot<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> > (__comp=..., __last=..., __first=...)
     at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1931
 #5  std::__introsort_loop<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, int, __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> > (__first=..., __last=...,
     __depth_limit=<optimized out>, __depth_limit@entry=9, __comp=__comp@entry=...) at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1962
 #6  0x00000000005e1db8 in std::__introsort_loop<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, int, __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> > (__first=..., __last=...,
     __depth_limit=<optimized out>, __depth_limit@entry=10, __comp=__comp@entry=...) at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1964
 #7  0x00000000005dd6fd in std::__sort<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, __gnu_cxx::__ops::_Iter_comp_iter<bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> > (__comp=..., __last=..., __first=...)
     at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:1979
 #8  std::sort<QTypedArrayData<Imap::Mailbox::TreeItem*>::iterator, bool (*)(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)> (__first=..., __last=..., __first=..., __last=...,
     __comp=0x5d3130 <(anonymous namespace)::MailboxNameComparator(Imap::Mailbox::TreeItem const*, Imap::Mailbox::TreeItem const*)>) at /nix/store/v819nrv8d33ns36gm4v9vqydq1v95axi-gcc-10.3.0/include/c++/10.3.0/bits/stl_algo.h:4899
 #9  Imap::Mailbox::Model::finalizeList (this=0xbfbdb0, parser=<optimized out>, mailboxPtr=0x7ffffffe4438) at /home/jkt/work/prog/trojita/src/Imap/Model/Model.cpp:352
 #10 0x000000000061d512 in Imap::Mailbox::ListChildMailboxesTask::handleStateHelper (this=0x124d790, resp=0x124e840) at /home/jkt/work/prog/trojita/src/Imap/Tasks/ListChildMailboxesTask.cpp:96
 #11 0x00000000005deadc in Imap::Mailbox::Model::responseReceived (this=0xbfbdb0, it=...) at /home/jkt/work/prog/trojita/src/Imap/Model/Model.cpp:220
 #12 0x00007ffff396918c in QObject::event(QEvent*) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #13 0x00007ffff441776f in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Widgets.so.5
 #14 0x00007ffff393c40a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #15 0x00007ffff393f451 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #16 0x00007ffff3994d93 in ?? () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #17 0x00007ffff1883aab in g_main_context_dispatch () from /nix/store/1qiv23m1q9fk18rwkzrk29ciz87030lp-glib-2.70.1/lib/libglib-2.0.so.0
 #18 0x00007ffff1883d58 in g_main_context_iterate.constprop () from /nix/store/1qiv23m1q9fk18rwkzrk29ciz87030lp-glib-2.70.1/lib/libglib-2.0.so.0
 #19 0x00007ffff1883e0f in g_main_context_iteration () from /nix/store/1qiv23m1q9fk18rwkzrk29ciz87030lp-glib-2.70.1/lib/libglib-2.0.so.0
 #20 0x00007ffff39943f0 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #21 0x00007ffff393adab in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #22 0x00007ffff39433a0 in QCoreApplication::exec() () from /nix/store/fwc2c76yqyyj0pj6abvsyzlgd2r1rvr0-qtbase-5.15.3/lib/libQt5Core.so.5
 #23 0x000000000047fafb in main (argc=<optimized out>, argv=0x7ffffffe4b80) at /home/jkt/work/prog/trojita/src/Gui/main.cpp:205
Edited by Jan Kundrát

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