Hi all. I’m trying to figure out what appears to be a double dealloc problem of some sort. I’m sure the actual bug is in my code (I’m trying to get a window with complex subsidiary windows, etc., to disassemble and free the things it owns, without freeing itself), but the backtrace at the point that the crash happens doesn’t have any of my code in it at all. I’ve appended the full backtrace below my signature, in case it is informative; maybe somebody has seen this pattern before and knows what I’m likely to be doing wrong. My code does not use QFontCache or QScopedPointer at all, so it’s hard to guess where my bug might be.
My question, though, is bigger: how would folks here recommend debugging a
double dealloc in a Qt-based app, running under Qt Creator? I’m coming from
the Cocoa/Xcode world, and in that world there’s a very nice tool called
NSZombie: you set a flag, and then whenever an object would be deallocated, it
instead turns into an NSZombie object that produces nice console logs if
anybody ever tries to use that memory as an object again. But that’s for
NSObject. Is there something similar in the Qt world, such that I could get a
console log or a break in the debugger at the point where a C++/Qt object that
has been dealloced gets touched again? Or if not, how would you recommend
approaching this? Thanks for any help.
Cheers,
-B.
Benjamin C. Haller
Messer Lab
Cornell University
1 QScopedPointer<QObjectData,
QScopedPointerDeleter<QObjectData>>::operator->() const
qscopedpointer.h 118 0x10201b594
2 decltype(fp.operator->()) qGetPtrHelper<QScopedPointer<QObjectData,
QScopedPointerDeleter<QObjectData>> const>(QScopedPointer<QObjectData,
QScopedPointerDeleter<QObjectData>> const&)
qglobal.h
1133 0x10201b594
3 QObject::d_func() const
qobject.h
132 0x10201b594
4 QObject::thread() const
qobject.cpp
1512 0x10201b594
5 QOpenGLVertexArrayObjectPrivate::destroy()
qopenglvertexarrayobject.cpp
212 0x101b21481
6 QOpenGLVertexArrayObject::destroy()
qopenglvertexarrayobject.cpp
424 0x101b217cc
7 QOpenGLVertexArrayObject::~QOpenGLVertexArrayObject()
qopenglvertexarrayobject.cpp
392 0x101b217c3
8 QOpenGLVertexArrayObject::~QOpenGLVertexArrayObject()
qopenglvertexarrayobject.cpp
391 0x101b217b9
9 QOpenGLTextureGlyphCache::~QOpenGLTextureGlyphCache()
qopengltextureglyphcache.cpp
93 0x101b1cacd
10 QOpenGLTextureGlyphCache::~QOpenGLTextureGlyphCache()
qopengltextureglyphcache.cpp
88 0x101b1cbce
11 QOpenGLTextureGlyphCache::~QOpenGLTextureGlyphCache()
qopengltextureglyphcache.cpp
88 0x101b1cbc9
12
QExplicitlySharedDataPointer<QFontEngineGlyphCache>::~QExplicitlySharedDataPointer()
qshareddata.h
184 0x101883c92
13
QExplicitlySharedDataPointer<QFontEngineGlyphCache>::~QExplicitlySharedDataPointer()
qshareddata.h
184 0x101883c74
14 QFontEngine::GlyphCacheEntry::~GlyphCacheEntry()
qfontengine.cpp
1570 0x101883c74
15 QFontEngine::GlyphCacheEntry::~GlyphCacheEntry()
qfontengine.cpp
1569 0x101883c74
16 void
std::allocator_traits<std::allocator<std::__list_node<QFontEngine::GlyphCacheEntry,
void
*>>>::__destroy<QFontEngine::GlyphCacheEntry>(std::integral_constant<bool,
false>, std::allocator<std::__list_node<QFontEngine::GlyphCacheEntry, void
*>>&, QFontEngine::GlyphCacheEntry *) memory
1732 0x101883c74
17 void
std::allocator_traits<std::allocator<std::__list_node<QFontEngine::GlyphCacheEntry,
void
*>>>::destroy<QFontEngine::GlyphCacheEntry>(std::allocator<std::__list_node<QFontEngine::GlyphCacheEntry,
void *>>&, QFontEngine::GlyphCacheEntry *)
memory 1595 0x101883c74
18 std::__list_imp<QFontEngine::GlyphCacheEntry,
std::allocator<QFontEngine::GlyphCacheEntry>>::clear()
list 733 0x101883c74
19 std::__list_imp<QFontEngine::GlyphCacheEntry,
std::allocator<QFontEngine::GlyphCacheEntry>>::~__list_imp()
list 712 0x101883c24
20 std::list<QFontEngine::GlyphCacheEntry>::~list()
list
805 0x101883c24
21 std::list<QFontEngine::GlyphCacheEntry>::~list()
list
805 0x101883c24
22 QHashNode<void const *,
std::list<QFontEngine::GlyphCacheEntry>>::~QHashNode()
qhash.h 147 0x101883c24
23 QHashNode<void const *,
std::list<QFontEngine::GlyphCacheEntry>>::~QHashNode()
qhash.h 147 0x101883c24
24 QHash<void const *,
std::list<QFontEngine::GlyphCacheEntry>>::deleteNode2(QHashData::Node *)
qhash.h 563 0x101883c24
25 QHashData::free_helper(void ( *)(QHashData::Node *))
qhash.cpp
572 0x101e5db39
26 QHash<void const *,
std::list<QFontEngine::GlyphCacheEntry>>::freeData(QHashData *)
qhash.h 603 0x10187a47b
27 QHash<void const *, std::list<QFontEngine::GlyphCacheEntry>>::~QHash()
qhash.h
250 0x10187a46f
28 QHash<void const *, std::list<QFontEngine::GlyphCacheEntry>>::~QHash()
qhash.h
250 0x10187a44f
29 QFontEngine::~QFontEngine()
qfontengine.cpp
277 0x10187a44f
30 QCoreTextFontEngine::~QCoreTextFontEngine()
qfontengine_coretext.mm
215 0x105b7cf8e
31 QCoreTextFontEngine::~QCoreTextFontEngine()
qfontengine_coretext.mm
215 0x105b7cf89
32 QFontEngineMulti::~QFontEngineMulti()
qfontengine.cpp
1782 0x101880039
33 QFontEngineMulti::~QFontEngineMulti()
qfontengine.cpp
1778 0x10188012e
34 QFontEngineMulti::~QFontEngineMulti()
qfontengine.cpp
1778 0x101880129
35 QFontCache::clear()
qfont.cpp
2861 0x1018762eb
36 QFontCache::~QFontCache()
qfont.cpp
2817 0x10187603c
37 QFontCache::~QFontCache()
qfont.cpp
2816 0x1018763ee
38 QFontCache::~QFontCache()
qfont.cpp
2816 0x1018763e9
39 QThreadStorageData::set(void *)
qthreadstorage.cpp
162 0x101e25777
40 QGuiApplicationPrivate::~QGuiApplicationPrivate()
qguiapplication.cpp
1694 0x1017ca490
41 QApplicationPrivate::~QApplicationPrivate()
qapplication.cpp
184 0x10116f81e
42 QApplicationPrivate::~QApplicationPrivate()
qapplication.cpp
184 0x10116f819
43 QScopedPointerDeleter<QObjectData>::cleanup(QObjectData *)
qscopedpointer.h
60 0x10201c06c
44 QScopedPointer<QObjectData,
QScopedPointerDeleter<QObjectData>>::~QScopedPointer()
qscopedpointer.h 107 0x10201c061
45 QScopedPointer<QObjectData,
QScopedPointerDeleter<QObjectData>>::~QScopedPointer()
qscopedpointer.h 105 0x10201c05d
46 QObject::~QObject()
qobject.cpp
1119 0x10201c05d
47 QApplication::~QApplication()
qapplication.cpp
837 0x101171b3d
48 main
main.cpp
246 0x100012256
49 start
(x86_64)
/usr/lib/system/libdyld.dylib 0x7fff6b461cc9
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