Valgrind and Memory leak

[Krish_ng]

I need to check the leaks in my application.I am using valgrind for this purpose.I hav deleted all objects that are created using new operator.I had used setWindowIcon() to set
the ICon for the main window.When i commented the statement there is a decrease in the
--definitely lost row of valgrind. Any reason why there is decrease in this row.Can anybody
suggest places where actually memory leaks occur.

[wysota]

Isn't this a double thread?

If not, are you sure the leak actually occurs? Qt doesn't cause any memory leaks on its own, Trolltech puts much effort to assure that. If you really have a leak, it might be caused by the platform itself.

[Krish_ng]

Any idea of platform leaks???

[wysota]

Did you check that you actually have a leak?

[Krish_ng]

This is the Leak summary i am gettting when i run my application using valgrind:
definitely lost:5689b in 118 blocks
possibly lost:0 b in 0 blocks
still reachable:295030b in 927 blocks
supressed:0 byts in 0 blocks

Can suggest wer actually leak is there..some lines from valgrind log

---QDialog::done(int)
QDialog::accept()
QMyDialog::closeEvent(QCloseEvent *)
QWidget::event(QEvent *)

[wysota]

Did you use --leak-check=full --leak-resolution=high and --show-reachable=yes Valgrind options?

[Krish_ng]

These are the options i have used:
valgrind -v --show-reachable=no --leak-check=full --run-libc-freeres=yes
When i commented the setWindowIcon() there is decrease in definitely lost row.

[wysota]

So please use the options I gave you. You'll get information about each potential leak. Then you'll be able to see if the leak comes from Qt or not.

[Krish_ng]

This some sample output from Valgrind:

Invalid read of size 4
at 0x4010DD3: (within /lib/ld-2.3.6.so)
by 0x4005F5B: (within /lib/ld-2.3.6.so)
by 0x4006431: (within /lib/ld-2.3.6.so)
by 0x4006A51: (within /lib/ld-2.3.6.so)
by 0x400A1F6: (within /lib/ld-2.3.6.so)
by 0x400B44E: (within /lib/ld-2.3.6.so)
by 0x400A3CA: (within /lib/ld-2.3.6.so)
by 0x43593D4: (within /lib/tls/i686/cmov/libc-2.3.6.so)

==5025== Address 0x43F1ED8 is 32 bytes inside a block of size 34 alloc'd
==5025== at 0x401D4B0: malloc (vg_replace_malloc.c:149)
==5025== by 0x4005DA5: (within /lib/ld-2.3.6.so)
==5025== by 0x4005EE5: (within /lib/ld-2.3.6.so)
==5025== by 0x4006431: (within /lib/ld-2.3.6.so)
==5025== by 0x43593D4: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025==
==5025== at 0x401D4B0: malloc (vg_replace_malloc.c:149)
==5025== by 0x400B540: (within /lib/ld-2.3.6.so)
==5025== by 0x4006DAF: (within /lib/ld-2.3.6.so)
==5025== by 0x400A1F6: (within /lib/ld-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x400A3CA: (within /lib/ld-2.3.6.so)
==5025== by 0x43593D4: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025==
==5025== Conditional jump or move depends on uninitialised value(s)
==5025== at 0x4010E21: (within /lib/ld-2.3.6.so)
==5025== by 0x4359072: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x85DD0A6: QLibraryPrivate::load_sys() (in /home/SourceCode/myFile)
==5025== by 0x85D83D3: QLibraryPrivate::load() (in /home/SourceCode/myFile)
==5025== by 0x85D86B0: QLibraryPrivate::loadPlugin() (in /home/SourceCode/myFile)
==5025== by 0x85D4719: QFactoryLoader::instance(QString const&) const (in /home/SourceCode/myFile)
==5025== by 0x80EF9A0: createReadHandler(QIODevice*, QByteArray const&) (in /home/SourceCode/myFile)
==5025== by 0x80F0F29: QImageReaderPrivate::initHandler() (in /home/SourceCode/myFile)
==5025==
==5025== Conditional jump or move depends on uninitialised value(s)
==5025== at 0x4010E2C: (within /lib/ld-2.3.6.so)
==5025== by 0x4359072: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x85DD0A6: QLibraryPrivate::load_sys() (in /home/SourceCode/myFile)
==5025== by 0x85D83D3: QLibraryPrivate::load() (in /home/SourceCode/myFile)
==5025== by 0x85D86B0: QLibraryPrivate::loadPlugin() (in /home/SourceCode/myFile)
==5025== by 0x85D4719: QFactoryLoader::instance(QString const&) const (in /home/SourceCode/myFile)
==5025== by 0x80EF9A0: createReadHandler(QIODevice*, QByteArray const&) (in /home/SourceCode/myFile)
==5025== by 0x80F0F29: QImageReaderPrivate::initHandler() (in /home/SourceCode/myFile)
==5025==
==5025== Conditional jump or move depends on uninitialised value(s)
==5025== at 0x4010D14: (within /lib/ld-2.3.6.so)
==5025== by 0x4006704: (within /lib/ld-2.3.6.so)
==5025== by 0x435936F: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x85DD0A6: QLibraryPrivate::load_sys() (in /home/SourceCode/myFile)
==5025== by 0x85D83D3: QLibraryPrivate::load() (in /home/SourceCode/myFile)
==5025== by 0x85D86B0: QLibraryPrivate::loadPlugin() (in /home/SourceCode/myFile)
==5025==
==5025== Conditional jump or move depends on uninitialised value(s)
==5025== at 0x4010E2C: (within /lib/ld-2.3.6.so)
==5025== by 0x4006704: (within /lib/ld-2.3.6.so)
==5025== by 0x435936F: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x85DD0A6: QLibraryPrivate::load_sys() (in /home/SourceCode/myFile)
==5025== by 0x85D83D3: QLibraryPrivate::load() (in /home/SourceCode/myFile)
==5025== by 0x85D86B0: QLibraryPrivate::loadPlugin() (in /home/SourceCode/myFile)
==5025==
==5025== Conditional jump or move depends on uninitialised value(s)
==5025== at 0x4010E2C: (within /lib/ld-2.3.6.so)
==5025== by 0x4004B78: (within /lib/ld-2.3.6.so)
==5025== by 0x4006792: (within /lib/ld-2.3.6.so)
==5025== by 0x435936F: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x85DD0A6: QLibraryPrivate::load_sys() (in /home/SourceCode/myFile)
==5025== by 0x85D83D3: QLibraryPrivate::load() (in /home/SourceCode/myFile)
==5025==
==5025== Invalid read of size 4
==5025== at 0x4010E00: (within /lib/ld-2.3.6.so)
==5025== by 0x4004B78: (within /lib/ld-2.3.6.so)
==5025== by 0x4006792: (within /lib/ld-2.3.6.so)
==5025== by 0x400A1F6: (within /lib/ld-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x400A3CA: (within /lib/ld-2.3.6.so)
==5025== by 0x43593D4: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== Address 0x4473950 is 24 bytes inside a block of size 25 alloc'd
==5025== at 0x401D4B0: malloc (vg_replace_malloc.c:149)
==5025== by 0x4006B83: (within /lib/ld-2.3.6.so)
==5025== by 0x400A1F6: (within /lib/ld-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x400A3CA: (within /lib/ld-2.3.6.so)
==5025== by 0x43593D4: (within /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x4358DDE: _dl_open (in /lib/tls/i686/cmov/libc-2.3.6.so)
==5025== by 0x412ED8D: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x400B44E: (within /lib/ld-2.3.6.so)
==5025== by 0x412F42C: (within /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025== by 0x412ED20: dlopen (in /lib/tls/i686/cmov/libdl-2.3.6.so)
==5025==
==5025== Syscall param write(buf) points to uninitialised byte(s)
==5025== at 0x4000792: (within /lib/ld-2.3.6.so)
==5025== by 0x407229E: _X11TransWrite (in /usr/lib/libX11.so.6.2.0)
==5025== by 0x4077BD5: (within /usr/lib/libX11.so.6.2.0)
==5025== by 0x4077CAA: _XReply (in /usr/lib/libX11.so.6.2.0)
==5025== by 0x405DF70: XInternAtom (in /usr/lib/libX11.so.6.2.0)
==5025== by 0x4071DCA: XSetWMProperties (in /usr/lib/libX11.so.6.2.0)
==5025== by 0x80D4DB6: QWidgetPrivate::create_sys(unsigned long, bool, bool) (in /home/SourceCode/myFile)
==5025== by 0x80ABF2E: QWidget::create(unsigned long, bool, bool) (in /home/SourceCode/myFile)
==5025== by 0x80ACEC9: QWidgetPrivate::createWinId(unsigned long) (in /home/SourceCode/myFile)
==5025== by 0x80ACFC2: QWidgetPrivate::setWindowTitle_helper(QString const&) (in /home/SourceCode/myFile)
==5025== by 0x80AD2F6: QWidget::setWindowTitle(QString const&) (in /home/SourceCode/myFile)
==5025== by 0x8069955: myClass::myClass() (in /home/SourceCode/myFile)
==5025== Address 0x446B9F8 is 192 bytes inside a block of size 16,384 alloc'd
==5025== at 0x401C7EF: calloc (vg_replace_malloc.c:279)
==5025== by 0x4062CBD: XOpenDisplay (in /usr/lib/libX11.so.6.2.0)
==5025== by 0x80C00E3: qt_init(QApplicationPrivate*, int, _XDisplay*, unsigned long, unsigned long) (in /home/SourceCode/myFile)
==5025== by 0x807CCF8: QApplicationPrivate::construct(_XDisplay*, unsigned long, unsigned long) (in /home/SourceCode/myFile)
==5025== by 0x807DABD: QApplication::QApplication(int&, char**, int) (in /home/SourceCode/myFile)
==5025== by 0x806EC19: main (in /home/SourceCode/myFile)

==5025== LEAK SUMMARY:
==5025== definitely lost: 5,689 bytes in 118 blocks.
==5025== possibly lost: 0 bytes in 0 blocks.
==5025== still reachable: 295,030 bytes in 927 blocks.
==5025== suppressed: 0 bytes in 0 blocks.

i hav tried the option posted by you.This is the result shown by valgrind

[wysota]

I don't see any leak reports here. Did you compile with debug information (like -g option to g++)? A leak report should be something like the following:


==9626== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==9626== at 0x401F91C: operator new[](unsigned) (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==9626== by 0x8048460: main (t.cpp:5)

Anyway you can see in your report that most of the notes are caused by libc, libdl and your code.

[Krish_ng]

==5025== LEAK SUMMARY:
==5025== definitely lost: 5,689 bytes in 118 blocks.
==5025== possibly lost: 0 bytes in 0 blocks.
==5025== still reachable: 295,030 bytes in 927 blocks.
==5025== suppressed: 0 bytes in 0 blocks.

Then wat this leak summary says...Does it mean leak is there...I hav not tried debug option.Any idea??

[wysota]

Try compiling with debug information so that valgrind can trace function calls. Anyway I don't think there is a leak in Qt (based on this report you pasted). I suggest you correct the things pointed out in your code though.

[Krish_ng]

I hav to try with debug..If the leak is not from Qt it should be from my appliction..The leak summary gives some leakage..