[Interest] Callgrind under Linux

Jérôme Godbout godboutj at amotus.ca
Fri Mar 6 15:47:41 CET 2020 

We did find a closed issue about it: https://bugreports.qt.io/browse/QTBUG-62118
But no solution or hint about the cause of this.

From: Interest <interest-bounces at qt-project.org> On Behalf Of Jérôme Godbout
Sent: March 6, 2020 9:27 AM
To: interest at qt-project.org
Subject: [Interest] Callgrind under Linux

Hi,
one of my colleague is trying to start valgrind callgrind to profile a part of the application using Qt 5.12.7, latest Qt Creator with Ubuntu. the start command look like this:

valgrind --tool=callgrind --instr-atstart=no ./OpM-3_DU_SW

it did the macro for the start/stop and dump. Added the valgrind lib. But Valgrind seem to crash with the following error:

==13393== Callgrind, a call-graph generating cache profiler
==13393== Copyright (C) 2002-2015, and GNU GPL'd, by Josef Weidendorfer et al.
==13393== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==13393== Command: ./OpM-3_DU_SW
==13393==
==13393== For interactive control, run 'callgrind_control -h'.
No active callgrind runs detected.
==13393== warning: ignoring line info entry with huge line number (1302938)
==13393==          Can't handle line numbers greater than 1048575, sorry
==13393== (Nb: this message is only shown once)
vex amd64->IR: unhandled instruction bytes: 0xF 0xC7 0xF2 0xB9 0x1 0x0 0x0 0x0
vex amd64->IR:   REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0
vex amd64->IR:   VEX=0 VEX.L=0 VEX.nVVVV=0x0 ESC=0F
vex amd64->IR:   PFX.66=0 PFX.F2=0 PFX.F3=0
==13393== valgrind: Unrecognised instruction at address 0x84d5c40.
==13393==    at 0x84D5C40: qt_random_cpu(void*, long long) (immintrin.h:103)
==13393==    by 0x84D6666: QRandomGenerator::SystemGenerator::generate(unsigned int*, unsigned int*) (qrandom.cpp:369)
==13393==    by 0x84D7068: QRandomGenerator::_fillRange(void*, void*) (qrandom.cpp:1226)
==13393==    by 0x853378B: qt_create_qhash_seed() (qrandom.h:143)
==13393==    by 0x8534136: QHashData::detach_helper(void (*)(QHashData::Node*, void*), void (*)(QHashData::Node*), int, int) (qhash.cpp:325)
==13393==    by 0x86B868E: QMetaType::registerConverterFunction(QtPrivate::AbstractConverterFunction const*, int, int) (qhash.h:599)
==13393==    by 0x6819C02: QMetaTypeId<QList<QMediaResource> >::qt_metatype_id() (qmetatype.h:2310)
==13393==    by 0x40106B9: call_init.part.0 (dl-init.c:72)
==13393==    by 0x40107CA: _dl_init (dl-init.c:30)
==13393==    by 0x4000C69: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)
==13393== Your program just tried to execute an instruction that Valgrind
==13393== did not recognise.  There are two possible reasons for this.
==13393== 1. Your program has a bug and erroneously jumped to a non-code
==13393==    location.  If you are running Memcheck and you just saw a
==13393==    warning about a bad jump, it's probably your program's fault.
==13393== 2. The instruction is legitimate but Valgrind doesn't handle it,
==13393==    i.e. it's Valgrind's fault.  If you think this is the case or
==13393==    you are not sure, please let us know and we'll try to fix it.
==13393== Either way, Valgrind will now raise a SIGILL signal which will
==13393== probably kill your program.
==13393==
==13393== Process terminating with default action of signal 4 (SIGILL)
==13393==  Illegal opcode at address 0x84D5C40
==13393==    at 0x84D5C40: qt_random_cpu(void*, long long) (immintrin.h:103)
==13393==    by 0x84D6666: QRandomGenerator::SystemGenerator::generate(unsigned int*, unsigned int*) (qrandom.cpp:369)
==13393==    by 0x84D7068: QRandomGenerator::_fillRange(void*, void*) (qrandom.cpp:1226)
==13393==    by 0x853378B: qt_create_qhash_seed() (qrandom.h:143)
==13393==    by 0x8534136: QHashData::detach_helper(void (*)(QHashData::Node*, void*), void (*)(QHashData::Node*), int, int) (qhash.cpp:325)
==13393==    by 0x86B868E: QMetaType::registerConverterFunction(QtPrivate::AbstractConverterFunction const*, int, int) (qhash.h:599)
==13393==    by 0x6819C02: QMetaTypeId<QList<QMediaResource> >::qt_metatype_id() (qmetatype.h:2310)
==13393==    by 0x40106B9: call_init.part.0 (dl-init.c:72)
==13393==    by 0x40107CA: _dl_init (dl-init.c:30)
==13393==    by 0x4000C69: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)
==13393==
==13393== Events    : Ir
==13393== Collected : 0
==13393==
==13393== I   refs:      0

This ain't our application it's a client one, but how does one know what exactly is wrong!? The proint call stack seem legitimate to me.
Any tips on this would be welcome.

Side note: Any pro tips to monitor only application calls and filter out the system libs without specifying every system lib by hand?

Thanks,


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Jérôme Godbout
Développeur Logiciel Sénior /
Senior Software Developer
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