--- Begin Message ---
- To: Debian Bug Tracking System <submit@bugs.debian.org>
- Subject: libqt4-dev: using QHash or QSet results in type-punned pointer strict-aliasing warning
- From: "Wesley J. Landaker" <wjl@icecavern.net>
- Date: Mon, 21 Aug 2006 16:09:41 -0600
- Message-id: <20060821220941.32453.55604.reportbug@localhost>
Package: libqt4-dev
Version: 4.1.4-1
Severity: normal
Whenever I try to use QHash or QSet (which is built from QHash) I get a
billion warnings from qhash.h like the following:
/usr/include/qt4/QtCore/qhash.h:236: instantiated from ‘void
QHash<Key, T>::detach() [with Key = int, T = QHashDummyValue]’
/usr/include/qt4/QtCore/qhash.h:711: instantiated from ‘void
QHash<Key, T>::reserve(int) [with Key = int, T = QHashDummyValue]’
/usr/include/qt4/QtCore/qset.h:146: instantiated from ‘void
QSet<T>::reserve(int) [with T = int]’
/usr/include/qt4/QtCore/qset.h:204: instantiated from ‘QSet<T>
QList<T>::toSet() const [with T = int]’
example.cpp:194: instantiated from here
/usr/include/qt4/QtCore/qhash.h:477: warning: dereferencing type-punned
pointer will break strict-aliasing rules
The line of my actual code is usually when I'm doing something very
simple, like using operator[]. The same exact code replacing QHash for
QMap always gets rid of the warning.
Unfortunately, this isn't even a workaround, because QSet always uses
QHash, so to get a list of unique keys from a multimap:
QList<int> keys = multimap.keys().toSet()
This also results in the warning quoted above.
Anyway, the problem appears to be in the QHash detach_helper method,
where it does a lot of reinterpret casting and then deferences a
pointer. I haven't yet investigated what needs to be done to fix this code.
-- System Information:
Debian Release: testing/unstable
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Shell: /bin/sh linked to /bin/bash
Kernel: Linux 2.6.17-1-amd64-k8
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Versions of packages libqt4-dev depends on:
ii libaudio-dev 1.8-2 The Network Audio System (NAS). (d
ii libfreetype6-dev 2.2.1-2 FreeType 2 font engine, developmen
ii libgl1-mesa-dev [libgl-dev] 6.4.2-1.1 A free implementation of the OpenG
ii libglu1-mesa-dev [libglu-de 6.4.2-1.1 The OpenGL utility library -- deve
ii libglu1-xorg-dev 1:7.0.23 transitional package for Debian et
ii libice-dev 1:1.0.0-3 X11 Inter-Client Exchange library
ii libjpeg62-dev 6b-13 Development files for the IJG JPEG
ii libmng-dev 1.0.9-1 M-N-G library (Development headers
ii libpng12-dev [libpng12-0-de 1.2.8rel-5.2 PNG library - development
ii libqt4-core 4.1.4-1 Qt 4 core non-GUI functionality ru
ii libqt4-gui 4.1.4-1 Qt 4 core GUI functionality runtim
ii libqt4-qt3support 4.1.4-1 Qt 3 compatibility library for Qt
ii libqt4-sql 4.1.4-1 Qt 4 SQL database module
ii libsm-dev 1:1.0.0-4 X11 Inter-Client Exchange library
ii libx11-dev 2:1.0.0-8 X11 client-side library (developme
ii libxcursor-dev 1.1.5.2-5 X cursor management library (devel
ii libxext-dev 1:1.0.0-4 X11 miscellaneous extensions libra
ii libxft-dev 2.1.8.2-8 FreeType-based font drawing librar
ii libxi-dev 1:1.0.0-5 X11 Input extension library (devel
ii libxinerama-dev 1:1.0.1-4.1 X11 Xinerama extension library (de
ii libxmu-dev 1:1.0.1-3 X11 miscellaneous utility library
ii libxrandr-dev 2:1.1.0.2-4 X11 RandR extension library (devel
ii libxrender-dev 1:0.9.0.2-4 X Rendering Extension client libra
ii libxt-dev 1:1.0.0-5 X11 toolkit intrinsics library (de
ii x11proto-core-dev 7.0.4-3 X11 core wire protocol and auxilia
ii xlibmesa-gl-dev 1:7.0.23 transitional package for Debian et
ii zlib1g-dev 1:1.2.3-13 compression library - development
Versions of packages libqt4-dev recommends:
ii qt4-dev-tools 4.1.4-1 Qt 4 development tools
-- no debconf information
--- End Message ---