First time I start kdevelop 4.91x it crash with 

coredumpctl gdb 12977 
           PID: 12977 (kdevelop)
           UID: 1502 (bruno)
           GID: 1500 (ioda)
        Signal: 11 (SEGV)
     Timestamp: Thu 2016-08-04 13:46:48 CEST (17h ago)
  Command Line: kdevelop
    Executable: /usr/bin/kdevelop
 Control Group: /
         Slice: -.slice
       Boot ID: 1c9a5c8d89194aafa7426d74079a5e21
    Machine ID: 5796a69412fbda1c055a261856a26e81
      Hostname: qt-kt.labaroche.ioda.net
      Coredump: /var/lib/systemd/coredump/core.kdevelop.1502.1c9a5c8d89194aafa7426d74079a5e21.12977.1470311208000000.xz
       Message: Process 12977 (kdevelop) of user 1502 dumped core.

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Reading symbols from /usr/bin/kdevelop...Reading symbols from /usr/lib/debug/usr/bin/kdevelop.debug...done.
done.
[New LWP 13140]
[New LWP 12977]
[New LWP 12983]
[New LWP 12982]
[New LWP 13148]
[New LWP 13146]
[New LWP 13134]
[New LWP 13139]
[New LWP 13142]
[New LWP 13147]
[New LWP 13144]
[New LWP 13143]
[New LWP 13141]
[New LWP 12978]
[New LWP 13145]
[New LWP 12979]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Core was generated by `kdevelop'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  std::__atomic_base<int>::operator++ (this=0x8) at /usr/include/c++/6/bits/atomic_base.h:296
296           { return __atomic_add_fetch(&_M_i, 1, memory_order_seq_cst); }
[Current thread is 1 (Thread 0x7f98fd7c7700 (LWP 13140))]
(gdb) bt
#0  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (this=0x8) at /usr/include/c++/6/bits/atomic_base.h:296
#1  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (_q_value=...) at /usr/include/qt5/QtCore/qatomic_cxx11.h:134
#2  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (this=0x8) at /usr/include/qt5/QtCore/qbasicatomic.h:127
#3  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (adata=0x0, this=0x7f98fd7c5cb0) at /usr/include/qt5/QtCore/qshareddata.h:258
#4  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (data=0x0, this=0x7f98fd7c5cb0) at /usr/src/debug/kdevplatform-4.90.91/language/duchain/types/typepointer.h:50
#5  0x00007f99223624ec in KDevelop::AbstractType::indexed() const (this=0x0) at /usr/src/debug/kdevplatform-4.90.91/language/duchain/types/abstracttype.cpp:99
#6  0x00007f99222d63e5 in KDevelop::Declaration::setAbstractType(KDevelop::TypePtr<KDevelop::AbstractType>) (this=this@entry=0x7f98f0056420, type=...)
    at /usr/src/debug/kdevplatform-4.90.91/language/duchain/declaration.cpp:269
#7  0x00007f99222d666f in KDevelop::Declaration::~Declaration() (this=0x7f98f0056420, __in_chrg=<optimized out>)
    at /usr/src/debug/kdevplatform-4.90.91/language/duchain/declaration.cpp:193
#8  0x00007f99222d6769 in KDevelop::Declaration::~Declaration() (this=0x7f98f0056420, __in_chrg=<optimized out>)
    at /usr/src/debug/kdevplatform-4.90.91/language/duchain/declaration.cpp:197
#9  0x00007f99222b6da5 in KDevelop::DUContext::cleanIfNotEncountered(QSet<KDevelop::DUChainBase*> const&) (this=0x7f98f00564c0, encountered=...)
    at /usr/src/debug/kdevplatform-4.90.91/language/duchain/ducontext.cpp:1449
#10 0x00007f98c348f101 in Python::ContextBuilder::visitFunctionBody(Python::FunctionDefinitionAst*) (this=0x7f98fd7c6ac0)
    at /usr/include/kdevplatform/language/duchain/builders/abstractcontextbuilder.h:480
#11 0x00007f98c348f101 in Python::ContextBuilder::visitFunctionBody(Python::FunctionDefinitionAst*) (this=0x7f98fd7c6ac0, node=<optimized out>)
    at /usr/src/debug/kdev-python-4.90.91/duchain/contextbuilder.cpp:477
#12 0x00007f98c34a1534 in Python::DeclarationBuilder::visitFunctionDefinition(Python::FunctionDefinitionAst*) (this=0x7f98fd7c6ac0, node=0x7f98f00787a0)
    at /usr/src/debug/kdev-python-4.90.91/duchain/declarationbuilder.cpp:1604
#13 0x00007f98c349a5fb in Python::DeclarationBuilder::visitClassDefinition(Python::ClassDefinitionAst*) (this=0x7f98fd7c6ac0, node=0x7f98f00870a0)
    at /usr/src/debug/kdev-python-4.90.91/duchain/declarationbuilder.cpp:1517
#14 0x00007f98e04495dc in Python::AstDefaultVisitor::visitCode(Python::CodeAst*) (this=this@entry=0x7f98fd7c6b18, node=node@entry=0x7f98f0044330)
    at /usr/src/debug/kdev-python-4.90.91/parser/astdefaultvisitor.cpp:79
#15 0x00007f98c34906c2 in Python::ContextBuilder::visitCode(Python::CodeAst*) (this=this@entry=0x7f98fd7c6ac0, node=node@entry=0x7f98f0044330)
    at /usr/src/debug/kdev-python-4.90.91/duchain/contextbuilder.cpp:319
#16 0x00007f98c3494f31 in Python::DeclarationBuilder::visitCode(Python::CodeAst*) (this=0x7f98fd7c6ac0, node=0x7f98f0044330)
    at /usr/src/debug/kdev-python-4.90.91/duchain/declarationbuilder.cpp:367
#17 0x00007f98c34a5777 in KDevelop::AbstractTypeBuilder<Python::Ast, Python::Identifier, Python::ContextBuilder>::supportBuild(Python::Ast*, KDevelop::DUContext*) (context=0x7f98f00952c0, node=0x7f98f0044330, this=0x7f98fd7c6ac0) at /usr/include/kdevplatform/language/duchain/builders/abstractcontextbuilder.h:134
#18 0x00007f98c34a5777 in KDevelop::AbstractTypeBuilder<Python::Ast, Python::Identifier, Python::ContextBuilder>::supportBuild(Python::Ast*, KDevelop::DUContext*) (this=0x7f98fd7c6ac0, node=0x7f98f0044330, context=<optimized out>) at /usr/include/kdevplatform/language/duchain/builders/abstracttypebuilder.h:85
#19 0x00007f98c348f93a in Python::ContextBuilder::build(KDevelop::IndexedString const&, Python::Ast*, KDevelop::ReferencedTopDUContext) (updateContext=..., node=0x7f98f0044330, url=..., this=0x7f98fd7c6ac0) at /usr/include/kdevplatform/language/duchain/builders/abstractcontextbuilder.h:114
#20 0x00007f98c348f93a in Python::ContextBuilder::build(KDevelop::IndexedString const&, Python::Ast*, KDevelop::ReferencedTopDUContext) (this=this@entry=0x7f98fd7c6ac0, url=..., node=node@entry=0x7f98f0044330, updateContext=...) at /usr/src/debug/kdev-python-4.90.91/duchain/contextbuilder.cpp:74
#21 0x00007f98c3494b05 in Python::DeclarationBuilder::build(KDevelop::IndexedString const&, Python::Ast*, KDevelop::ReferencedTopDUContext) (this=this@entry=0x7f98fd7c6ac0, url=..., node=0x7f98f0044330, updateContext=...) at /usr/src/debug/kdev-python-4.90.91/duchain/declarationbuilder.cpp:107
#22 0x00007f98d00871c7 in Python::ParseJob::run(QSharedPointer<ThreadWeaver::JobInterface>, ThreadWeaver::Thread*) (this=0xc48e60)
    at /usr/src/debug/kdev-python-4.90.91/pythonparsejob.cpp:170
#23 0x00007f99198401da in ThreadWeaver::IdDecorator::run(QSharedPointer<ThreadWeaver::JobInterface>, ThreadWeaver::Thread*) (this=<optimized out>, self=..., thread=0xcc73b0)
    at /usr/src/debug/threadweaver-5.24.0/src/iddecorator.cpp:69
#24 0x00007f99198407e8 in ThreadWeaver::Executor::run(QSharedPointer<ThreadWeaver::JobInterface> const&, ThreadWeaver::Thread*) (this=<optimized out>, job=..., thread=<optimized out>)
    at /usr/src/debug/threadweaver-5.24.0/src/executor.cpp:52
#25 0x00007f991983f340 in ThreadWeaver::Job::execute(QSharedPointer<ThreadWeaver::JobInterface> const&, ThreadWeaver::Thread*) (this=<optimized out>, self=..., th=0xcc73b0)
    at /usr/src/debug/threadweaver-5.24.0/src/job.cpp:83
#26 0x00007f991983ee50 in ThreadWeaver::Thread::run() (this=0xcc73b0) at /usr/src/debug/threadweaver-5.24.0/src/thread.cpp:114
#27 0x00007f992489e2d8 in QThreadPrivate::start(void*) (arg=0xcc73b0) at thread/qthread_unix.cpp:341
#28 0x00007f991d03c474 in start_thread (arg=0x7f98fd7c7700) at pthread_create.c:333
#29 0x00007f99241a93ed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
(gdb)

reproductible everytime