I had one project open, but no files. I then switched branches like that 
(starting at branch b)

git checkout master
git pull --rebase
git checkout b

Code is at 866d099e05ec5c4d0c9c02a715fd9e351260d753

May be related to bug 260741

*** Error in `./app/kdevelop': double free or corruption (fasttop): 
0x00007f798530b510 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x7abf6)[0x7f79cb38bbf6]
/lib64/libc.so.6(+0x7b973)[0x7f79cb38c973]
/usr/lib64/libQtCore.so.4(_ZN7QString4freeEPNS_4DataE+0xb8)[0x7f79cd3147d8]
/usr/lib64/libkdevplatformproject.so.6(_ZNK8KDevelop15ProjectBaseItem8lessThanEPKS0_+0x1aa)
[0x7f79ca3eb48a]
/usr/lib64/libQtGui.so.4(+0x7663e1)[0x7f79ccadb3e1]
/usr/lib64/libQtGui.so.4(+0x766736)[0x7f79ccadb736]
/usr/lib64/libQtGui.so.4(+0x76b04e)[0x7f79ccae004e]
/usr/lib64/libQtCore.so.4(_ZN7QObject5eventEP6QEvent+0x26e)[0x7f79cd3db68e]
/usr/lib64/libQtGui.so.4(_ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent+0xac)
[0x7f79cc55386c]
/usr/lib64/libQtGui.so.4(_ZN12QApplication6notifyEP7QObjectP6QEvent+0x13b)
[0x7f79cc557ceb]
/usr/lib64/libkdeui.so.5(_ZN12KApplication6notifyEP7QObjectP6QEvent+0x36)
[0x7f79cdbdf146]
/usr/lib64/libQtCore.so.4(_ZN16QCoreApplication14notifyInternalEP7QObjectP6QEvent+0x8e)
[0x7f79cd3c6c9e]
/usr/lib64/libQtCore.so.4(_ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData+0x421)
[0x7f79cd3ca601]
/usr/lib64/libQtCore.so.4(+0x1ac043)[0x7f79cd3f5043]
/usr/lib64/libglib-2.0.so.0(g_main_context_dispatch+0x135)[0x7f79c59c87d5]
/usr/lib64/libglib-2.0.so.0(+0x4ab08)[0x7f79c59c8b08]
/usr/lib64/libglib-2.0.so.0(g_main_context_iteration+0x34)[0x7f79c59c8bc4]
/usr/lib64/libQtCore.so.4(_ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE+0x66)
[0x7f79cd3f51d6]
/usr/lib64/libQtGui.so.4(+0x27ec1e)[0x7f79cc5f3c1e]
/usr/lib64/libQtCore.so.4(_ZN10QEventLoop13processEventsE6QFlagsINS_17ProcessEventsFlagEE+0x2f)
[0x7f79cd3c59ef]
/usr/lib64/libQtCore.so.4(_ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE+0x138)
[0x7f79cd3c5c78]
/usr/lib64/libQtCore.so.4(_ZN16QCoreApplication4execEv+0x88)[0x7f79cd3ca918]
./app/kdevelop[0x411f81]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7f79cb332a15]
./app/kdevelop[0x40a3b9]
======= Memory map: ========
00400000-00427000 r-xp 00000000 fd:00 12213927                           
/home/ebeer/repos/build/KDE/kdevelop/app/kdevelop
00626000-00627000 r--p 00026000 fd:00 12213927                           
/home/ebeer/repos/build/KDE/kdevelop/app/kdevelop
00627000-00628000 rw-p 00027000 fd:00 12213927                           
/home/ebeer/repos/build/KDE/kdevelop/app/kdevelop
0162d000-0a07f000 rw-p 00000000 00:00 0                                  
[heap]
7f792ef87000-7f7934000000 rw-s 00000000 fd:04 262594                     
/var/tmp/kdecache-ebeer/plasma_theme_default.kcache
7f7934000000-7f7935018000 rw-p 00000000 00:00 0 
7f7935018000-7f7938000000 ---p 00000000 00:00 0 
7f793c000000-7f793cd0b000 rw-p 00000000 00:00 0 
7f793cd0b000-7f7940000000 ---p 00000000 00:00 0 
7f794062b000-7f7940634000 rwxp 00000000 00:00 0 
7f7940700000-7f7940780000 rw-p 00000000 00:00 0 
7f794078e000-7f79407b3000 rwxp 00000000 00:00 0 
7f79407b3000-7f7940bc5000 rw-p 00000000 00:00 0 
7f7940bc5000-7f7940bc9000 rwxp 00000000 00:00 0 
7f7941448000-7f7941449000 ---p 00000000 00:00 0 
7f7941449000-7f7941c49000 rw-p 00000000 00:00 0                          
[stack:5714]
7f7941c49000-7f7941c4a000 ---p 00000000 00:00 0 
7f7941c4a000-7f794244a000 rw-p 00000000 00:00 0                          
[stack:5713]
7f79427b9000-7f794285e000 r--p 00000000 fd:01 803775                     
/usr/share/fonts/truetype/DejaVuSans-Bold.ttf
7f7942986000-7f7942a8e000 rw-p 00000000 00:00 0 
7f7942ab7000-7f7942b9e000 r--s 001fe000 fd:00 396385                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/Code Model
7f7942b9f000-7f7942ba0000 ---p 00000000 00:00 0 
7f7942ba0000-7f79433a0000 rw-p 00000000 00:00 0                          
[stack:21692]
7f79433a0000-7f79433bc000 r--p 00000000 fd:01 1181257                    
/usr/share/ghostscript/fonts/n021003l.pfb
7f79433bc000-7f79433d7000 r--p 00000000 fd:01 1181298                    
/usr/share/ghostscript/fonts/n021004l.pfb
7f79433d7000-7f79437ee000 rw-p 00000000 00:00 0 
7f79437ee000-7f79837ee000 rwxp 00000000 00:00 0 
7f79837ee000-7f798381b000 r-xp 00000000 fd:01 927440                     
/usr/lib64/qt4/plugins/bearer/libqnmbearer.so
7f798381b000-7f7983a1a000 ---p 0002d000 fd:01 927440                     
/usr/lib64/qt4/plugins/bearer/libqnmbearer.so
7f7983a1a000-7f7983a1c000 r--p 0002c000 fd:01 927440                     
/usr/lib64/qt4/plugins/bearer/libqnmbearer.so
7f7983a1c000-7f7983a1d000 rw-p 0002e000 fd:01 927440                     
/usr/lib64/qt4/plugins/bearer/libqnmbearer.so
7f7983a1d000-7f7983a2a000 r-xp 00000000 fd:01 923575                     
/usr/lib64/qt4/plugins/bearer/libqgenericbearer.so
7f7983a2a000-7f7983c29000 ---p 0000d000 fd:01 923575                     
/usr/lib64/qt4/plugins/bearer/libqgenericbearer.so
7f7983c29000-7f7983c2a000 r--p 0000c000 fd:01 923575                     
/usr/lib64/qt4/plugins/bearer/libqgenericbearer.so
7f7983c2a000-7f7983c2b000 rw-p 0000d000 fd:01 923575                     
/usr/lib64/qt4/plugins/bearer/libqgenericbearer.so
7f7983c2b000-7f7983c68000 r-xp 00000000 fd:01 924108                     
/usr/lib64/qt4/plugins/bearer/libqconnmanbearer.so
7f7983c68000-7f7983e67000 ---p 0003d000 fd:01 924108                     
/usr/lib64/qt4/plugins/bearer/libqconnmanbearer.so
7f7983e67000-7f7983e69000 r--p 0003c000 fd:01 924108                     
/usr/lib64/qt4/plugins/bearer/libqconnmanbearer.so
7f7983e69000-7f7983e6a000 rw-p 0003e000 fd:01 924108                     
/usr/lib64/qt4/plugins/bearer/libqconnmanbearer.so
7f7983e6a000-7f7983f6a000 rw-p 00000000 00:00 0 
7f7983f6a000-7f7984000000 r--p 00000000 fd:01 788396                     
/usr/share/fonts/truetype/DejaVuSans-Oblique.ttf
7f7984000000-7f7985481000 rw-p 00000000 00:00 0 
7f7985481000-7f7988000000 ---p 00000000 00:00 0 
7f7988000000-7f7988611000 rw-p 00000000 00:00 0 
7f7988611000-7f798c000000 ---p 00000000 00:00 0 
7f798c000000-7f798c021000 rw-p 00000000 00:00 0 
7f798c021000-7f7990000000 ---p 00000000 00:00 0 
7f7990000000-7f799006f000 rw-p 00000000 00:00 0 
7f799006f000-7f7994000000 ---p 00000000 00:00 0 
7f799406a000-7f799406b000 r--s 00001000 fd:00 428338                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/19
7f799406b000-7f799406d000 r--s 00001000 fd:00 429162                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/401
7f799406d000-7f799406e000 r--s 00026000 fd:00 428582                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/400
7f799406e000-7f799406f000 r--s 00000000 fd:00 396640                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/21
7f799406f000-7f7994070000 r--s 00014000 fd:00 429421                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/20
7f7994070000-7f7994071000 r--s 00000000 fd:00 429231                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/1886
7f7994071000-7f799407c000 r--s 00002000 fd:00 396684                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/2820
7f799407c000-7f7994080000 r--s 00000000 fd:00 427385                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/topcontexts/2555
7f7994080000-7f79948db000 rw-s 00000000 00:04 64651332                   
/SYSV00000000 (deleted)
7f799492d000-7f7994967000 r--p 00000000 fd:01 788383                     
/usr/share/fonts/truetype/DejaVuSansMono-BoldOblique.ttf
7f7994967000-7f7994ae8000 r--s 001fe000 fd:00 396383                     
/home/ebeer/.kdevduchain/{95a7b251-388a-4183-9516-5147e030a2bb}/0/Persistent 
Declaration Table
7f7994ae8000-7f7994ae9000 ---p 00000000 00:00 0 
7f7994ae9000-7f79952e9000 rw-p 00000000 00:00 0                          
[stack:5496]
7f79952e9000-7f79952ea000 ---p 00000000 00:00 0 
7f79952ea000-7f7995aea000 rw-p 00000000 00:00 0                          
[stack:5498]
7f7995aea000-7f7995af7000 r-xp 00000000 fd:01 535243                     
/usr/lib64/qt4/plugins/sqldrivers/libqsqlite.so
7f7995af7000-7f7995cf6000 ---p 0000d000 fd:01 535243                     
/usr/lib64/qt4/plugins/sqldrivers/libqsqlite.so
7f7995cf6000-7f7995cf7000 r--p 0000c000 fd:01 535243                     
/usr/lib64/qt4/plugins/sqldrivers/libqsqlite.soKCrash: Application 'kdevelop' 
crashing...

[KCrash Handler]
#6  0x00007f79cb3463d5 in raise () from /lib64/libc.so.6
#7  0x00007f79cb347858 in abort () from /lib64/libc.so.6
#8  0x00007f79cb38607b in __libc_message () from /lib64/libc.so.6
#9  0x00007f79cb38bbf6 in malloc_printerr () from /lib64/libc.so.6
#10 0x00007f79cb38c973 in _int_free () from /lib64/libc.so.6
#11 0x00007f79cd3147d8 in QString::free (d=0x7f798530b510) at 
tools/qstring.cpp:1235
#12 0x00007f79ca3eb48a in ~QString (this=<optimized out>, __in_chrg=<optimized 
out>) at /usr/include/QtCore/qstring.h:880
#13 lessThan (item=0x7f79853b1cd0, this=0x7f79853b90e0) at 
/usr/src/debug/kdevplatform-1.4.1/project/projectmodel.cpp:380
#14 KDevelop::ProjectBaseItem::lessThan (this=0x7f79853b90e0, 
item=0x7f79853b1cd0) at 
/usr/src/debug/kdevplatform-1.4.1/project/projectmodel.cpp:366
#15 0x00007f79ccadb3e1 in 
QSortFilterProxyModelPrivate::proxy_intervals_for_source_items_to_add 
(this=this@entry=0x56af0e0, proxy_to_source=..., source_items=..., 
source_parent=..., orient=orient@entry=Qt::Vertical) at 
itemviews/qsortfilterproxymodel.cpp:614
#16 0x00007f79ccadb736 in QSortFilterProxyModelPrivate::insert_source_items 
(this=this@entry=0x56af0e0, source_to_proxy=..., proxy_to_source=..., 
source_items=..., source_parent=..., orient=orient@entry=Qt::Vertical, 
emit_signal=emit_signal@entry=false) at 
itemviews/qsortfilterproxymodel.cpp:673
#17 0x00007f79ccae004e in QSortFilterProxyModelPrivate::_q_sourceDataChanged 
(this=0x56af0e0, source_top_left=..., source_bottom_right=...) at 
itemviews/qsortfilterproxymodel.cpp:1182
#18 0x00007f79cd3db68e in QObject::event (this=0x56af0b0, e=<optimized out>) 
at kernel/qobject.cpp:1203
#19 0x00007f79cc55386c in QApplicationPrivate::notify_helper 
(this=this@entry=0x1668d40, receiver=receiver@entry=0x56af0b0, 
e=e@entry=0x7f798513fb10) at kernel/qapplication.cpp:4562
#20 0x00007f79cc557ceb in QApplication::notify (this=0x7fffb8647590, 
receiver=0x56af0b0, e=0x7f798513fb10) at kernel/qapplication.cpp:4423
#21 0x00007f79cdbdf146 in KApplication::notify (this=0x7fffb8647590, 
receiver=0x56af0b0, event=0x7f798513fb10) at 
/usr/src/debug/kdelibs-4.10.1/kdeui/kernel/kapplication.cpp:311
#22 0x00007f79cd3c6c9e in QCoreApplication::notifyInternal 
(this=0x7fffb8647590, receiver=receiver@entry=0x56af0b0, 
event=event@entry=0x7f798513fb10) at kernel/qcoreapplication.cpp:946
#23 0x00007f79cd3ca601 in sendEvent (event=0x7f798513fb10, receiver=0x56af0b0) 
at kernel/qcoreapplication.h:231
#24 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, 
data=0x162e840) at kernel/qcoreapplication.cpp:1570
#25 0x00007f79cd3f5043 in sendPostedEvents () at kernel/qcoreapplication.h:236
#26 postEventSourceDispatch (s=0x1667de0) at 
kernel/qeventdispatcher_glib.cpp:279
#27 0x00007f79c59c87d5 in g_main_context_dispatch () from 
/usr/lib64/libglib-2.0.so.0
#28 0x00007f79c59c8b08 in ?? () from /usr/lib64/libglib-2.0.so.0
#29 0x00007f79c59c8bc4 in g_main_context_iteration () from 
/usr/lib64/libglib-2.0.so.0
#30 0x00007f79cd3f51d6 in QEventDispatcherGlib::processEvents (this=0x1634140, 
flags=...) at kernel/qeventdispatcher_glib.cpp:424
#31 0x00007f79cc5f3c1e in QGuiEventDispatcherGlib::processEvents 
(this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#32 0x00007f79cd3c59ef in QEventLoop::processEvents 
(this=this@entry=0x7fffb86472f0, flags=...) at kernel/qeventloop.cpp:149
#33 0x00007f79cd3c5c78 in QEventLoop::exec (this=0x7fffb86472f0, flags=...) at 
kernel/qeventloop.cpp:204
#34 0x00007f79cd3ca918 in QCoreApplication::exec () at 
kernel/qcoreapplication.cpp:1218
#35 0x0000000000411f81 in main (argc=1, argv=0x7fffb8649548) at 
/home/ebeer/repos/KDE/kdevelop/app/main.cpp:518


Reproducible: Didn't try