How do I tell helgrind that some atomic operations on integers are OK?
A suppression like this works, but it would make helgrind more useful to all Qt
users if either atomic operations were handled automatically, or if this was
added to valgrind's own suppressions.
{
qt5_basic_atomic_integer
Helgrind:Race
fun:_ZNK19QBasicAtomicIntegerIiE4loadEv
}
Also, this only works for integers, not for pointers...
==8489== Possible data race during read of size 8 at 0x8B9C968 by thread #3
==8489== at 0x57549C0: QBasicAtomicPointer<QTextCodec>::loadAcquire() const
(qgenericatomic.h:110)
==8489== by 0x5753A26: QTextCodec::codecForLocale() (qtextcodec.cpp:683)
==8489== by 0x558BD08: QString::toLocal8Bit() const (qstring.cpp:3959)
==8489==
==8489== This conflicts with a previous write of size 8 by thread #2
==8489== at 0x57549A2:
QBasicAtomicPointer<QTextCodec>::storeRelease(QTextCodec*)
(qgenericatomic.h:119)
==8489== by 0x5757D5D: QIcuCodec::defaultCodecUnlocked() (qicucodec.cpp:441)
==8489== by 0x5753A43: QTextCodec::codecForLocale() (qtextcodec.cpp:687)
==8489== by 0x558BD08: QString::toLocal8Bit() const (qstring.cpp:3959)
Can't make suppressions for these, given that the template class could use any
type
(here QTextCodec).
The implementation of loadAcquire/storeRelease is compiler and platform
dependent.
With C++11 it uses std::atomic, with gcc (in non-c++11 mode) it uses some
__sync_synchronize stuff,
on ARM there's a bit of assembly, etc.
I presume all this is too low-level for helgrind? I.e. can it actually detect
atomic operations
and therefore validate Qt's implementation, or should we rather just "trust Qt"
and aim for
silencing helgrind whenever it sees QBasicAtomic{Integer,Pointer}?
--
David Faure, fa...@kde.org, http://www.davidfaure.fr
Sponsored by Nokia to work on KDE, incl. KDE Frameworks 5
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