If you’re using LiteIde for golang development you may see that shortcuts for tab change (Ctrl+Tab and Ctrl+Shift+Tab) can’t be changed via settings. For somebody (like me) it’s a big usability problem – I have Ctrl+PgUp and Ctrl+PgDown in all other applications. But small change of code and recompilation helps as allways :) --- a/liteidex/src/liteapp/editormanager.cpp +++ b/liteidex/src/liteapp/editormanager.cpp @@ -270,9 +270,9 @@ bool EditorManager::eventFilter(QObject *target, QEvent *event) if (event->type() == QEvent::KeyPress)
Last time i do many thing starting from small utilities and up to big projects in golang. And many friends ask me why… first time i just said that golang is simple and cool :) But now i decided to do simple benchmark to show why… So, used interpreters/compilers: PHP: $ php --version PHP 5.6.4-4ubuntu6 (cli) (built: Apr 17 2015 15:47:51) Copyright (c) 1997-2014 The PHP Group Zend Engine v2.6.0, Copyright (c) 1998-2014 Zend Technologies with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2014, by Zend Technologies HHVM: $ hhvm --version HipHop VM 3.7.2 (rel) Compiler: tags/HHVM-3.7.2-0-gfc9f29b2799933d8215faaadfa83de722df64e26 Repo schema: 34f16546e395aed44ad434467b6f96c89b0d8a8b C: $ gcc --version gcc (Ubuntu 4.9.2-10ubuntu13) 4.9.2 Copyright (C) 2014 Free Software Foundation, Inc.
As you know QMap/QHash are little bit faster than std::map and std::unordered_map … but why? I have no ideas about this before I have used them in high-load muti-thread application. I send data in QHash via queued signal/slot between threads. Anything looks fine, but 1-2 times per day application gets segfault. It was very strange because it crashed after different count iterations but it was millions iterations. GDB shows something like this: #0 0x00007f8421029107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007f842102a4e8 in __GI_abort () at abort.c:89 #2 0x00007f8421067044 in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7f8421159c40 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175 #3 0x00007f842106c81e in malloc_printerr (action=1, str=0x7f8421159d90 "double free or corruption (out)", ptr=<optimized out>) at malloc.c:4996 #4 0x00007f842106d526 in _int_free (av=<optimized out>, p=<optimized out>, have_lock=0) at malloc.c:3840 #5 0x00007f8421ede054 in QHashData::free_helper (this=0x7f8418003a80, node_delete=0x40b324 <QHash<unsigned long, logdata>::deleteNode2(QHashData::Node*)>) at tools/qhash.cpp:496 #6 0x000000000040b364 in QHash<unsigned long, logdata>::freeData (this=0x7f84180bb5e0, x=0x7f8418003a80) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qhash.h:600 #7 0x000000000040f208 in QHash<unsigned long, logdata>::~QHash (this=0x7f84180bb5e0, __in_chrg=<optimized out>) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qhash.h:310 after some days of hard debug, Qt source code reading and liters of green tea i have found that different instances of QHash (and also QMap) may share some data structures.
What is is and why we need it? From the Qt documentation we know that “Qt’s meta-object system provides the signals and slots mechanism for inter-object communication, run-time type information, and the dynamic property system.” [1]. I hope everyone knows what is signal-slot in Qt and why you need Q_OBJECT macro at the beginning of each class declaration. Meta-object is also used for object casting using qobject_cast template function. It’s much more safe then build-in C++ cast functions and often is much faster.