I'm using precompiled headers on a Qt project to speed up compilation time. I'm using Qt 4.6.2 .When I compile the project using macx-g++ (meaning the g++ compiler) it doesn't include the stdafx.h automatically for each header. When compiling under xcode it will work. I'm using the PRECOMPILED_HEADER qmake constant to point at my stdafx.h.
So is it a limitation from g++? Or there a solution/work around?
Thanks for your help,
Boris -
Sometimes gcc ignores precompiled header if some conditions aren't met. see: gcc documentation page.
Compile headers just like any other files but put the output inside a file with a suffix of .gch:
g++ -c stdafx.h -o stdafx.h.gch
g++ main.cpp
./main.out
Related
I am statically linking an QT application, but for some reason when i open the executable i am getting errors for missing dlls.
Basically i am linking the following libs:
### LINKER FLAGS ###
LDFLAGS = -LC:/Qt/5.15.0/mingw81_32/lib
LDLIBS = -lQt5Widgets -lQt5Gui -lQt5Core
Why am i getting errors for missing dlls when i am statically linking everything?
The compilation and linking passes correctly, the executable is generated also..i have no idea why it needs dlls.
EDIT:
Missing dlls:
libgcc_s_dw2-1.dll,
libstdc++-6.dll,
Qt5Code.dll,
Qt5Widgets.dll
To elaborate on CristiFati's reply, you need a line like this in your project file:
QMAKE_LFLAGS += -static-libstdc++ -static-libgcc
though I'd prefer:
QMAKE_LFLAGS_RELEASE += -static-libstdc++ -static-libgcc
Note that if you want a truly standalone, self-contained binary, you'll need to build yourself a static Qt library. That's kind of a big deal, and unfortunately not as well documented as most of Qt-land is.
I used Qt 5.7 and gcc 4.9.2. Qt Core module throw Qt requires C++11 support error.
This page say that
gcc 4.9.2 fails to compile Qt.
So I installed gcc 4.8. I check using below command on terminal :
$ g++ --version
g++ (Ubuntu 4.8.4-1ubuntu15) 4.8.4
My kit uses cmake not qmake. I add TARGET_LINK_LIBRARIES ( xxxx yyyy /usr/bin/c++ -std=c++11 to CMakeLists-txt.
I restart my pc and run my application again. Same error is throwed.
/opt/Qt/5.7/gcc_64/include/QtCore/qbasicatomic.h:61: error: #error "Qt requires C++11 support"
# error "Qt requires C++11 support"
^
How can I solve it?
If using QtCreator, you can add this to your .pro file:
CONFIG += c++11
https://wiki.qt.io/How_to_use_C%2B%2B11_in_your_Qt_Projects
Its has been a while.
How I finally solve it is indicating in CMakeLists.txt the following line just after project(MyProject):
add_compile_options(-std=c++11)
That says to cmake, to create a Makefile that will use c++11 solving issues.
solution for me was (in your .pro file):
QMAKE_CXXFLAGS += -stdlib=libc++
QMAKE_CXXFLAGS += -std=c++11
QMAKE_CXXFLAGS += -mmacosx-version-min=10.7
QMAKE_LFLAGS += -mmacosx-version-min=10.7
Turn c++11 on explicitly:
set(CMAKE_CXX_FLAGS "-std=c++11" CACHE STRING "compile flags" FORCE) after project(...) declaration.
add_library(MyLib SHARED ${PROJECT_HEADERS} ${PROJECT_SOURCES})
...
set_property(TARGET MyLib PROPERTY CXX_STANDARD 11)
set_property(TARGET MyLib PROPERTY CXX_STANDARD_REQUIRED ON)
SOMETIMES, this will not be a configuration issue as mentioned in other answers. In my case, the problem was one file that happened to have been saved with a .CPP extension rather than .cpp. QMake (Qt5) was misidentifying the file and trying to compile it with the C compiler rather than the C++ compiler. The QMake from Qt4 was not exhibiting this issue. Renaming the file fixed the issue.
My comment at the time was "Could this really be that f&%%& simple!!"
I'm trying to get Qt5 working on Ubuntu 12.04. I downloaded the 32-bit installer from http://qt-project.org/downloads and basically just let it install everything in my home folder.
I had to add ~/Qt/5.1.0/gcc/bin to my path for qmake to work, but now when I try to make a hello qt example (using qt4 book), when running make, it cannot find the QApplication or QLabel header. When I replace them with QtWidgets/QApplication, it finds the header, but I get all undefined references when linking.
This is the command make executes:
g++ -c -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../Qt/5.1.0/gcc/mkspecs/linux-g++ -I. -I. -I../../../../Qt/5.1.0/gcc/include -I../../../../Qt/5.1.0/gcc/include/QtGui -I../../../../Qt/5.1.0/gcc/include/QtCore -I. -o hello.o hello.C
I managed to figure out that it's qmake -project that is doing something wrong. When I make an app in Qt Creator (which actually works), the .pro file has lines like QT += widgets, that are not there when I run it on the command line.
I found the answer using qmake --help. This actually says:
Note: The created .pro file probably will
need to be edited. For example add the QT variable to
specify what modules are required.
Adding these lines to the .pro file solved the problem:
QT += core gui
QT += widgets
As an alternative to manually editing the .pro file after running qmake -project, you can specify assignments on the command line that will be included in the generated files:
qmake -project "QT = core gui widgets"
See http://qt-project.org/doc/qt-5.1/qtdoc/qmake-running.html
I want to use Matlab's C API within QT (http://www.mathworks.com/help/techdoc/matlab_external/f39876.html#bsfvqhp-1) under Windows for opening a .mat file. In my .pro file I have included
INCLUDEPATH += "C:\Program Files\MATLAB\R2010b\extern\include"
which works fine (the code compiles). But when trying to link the libmat.lib file (I have read the .dll files cannot be linked directly) using
LIBS += -L"C:\Program Files\MATLAB\R2010b\extern\lib\win32\microsoft" -llibmat
the application crashes on execution. The error given says [file].exe exited with code -1073741515
I'm neither a QT nor a Windows expert but for this project I am forced to use both (I guess it would be easier to fix this in GNU/Linux) so any help would be appreciated. Using Windows XP, QT version 4.7.0 with Qt Creator 2.0.1, and Matlab R2010b.
The last output from the compiler just in case it is useful:
g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -Wl,-subsystem,windows -o debug/MainUI.exe debug/main.o debug/maingui.o debug/matparser.o debug/matutils.o debug/moc_maingui.o -L'c:/Qt/2010.05/qt/lib' -lmingw32 -lqtmaind "-LC:\Program Files\MATLAB\R2010b\extern\lib\win32\microsoft" -llibmat -lQtGuid4 -lQtCored4
I just tested building a simple C program that uses the MAT-File Interface Library with no problems. The example file is located in: matlabroot/examples/eng_mat/matcreat.c. I am compiling using MinGW on a Windows XP 32-bit machine. Here is the Makefile I used:
# root directory of MATLAB installation
MATLABROOT="/c/Program Files/MATLAB/R2010b"
.PHONY : all clean run
all: matcreat
matcreat:
gcc ${MATLABROOT}/extern/examples/eng_mat/matcreat.c -o matcreat \
-I${MATLABROOT}/extern/include \
-L${MATLABROOT}/extern/lib/win32/microsoft -llibmat -llibmx
clean:
rm -rf matcreat *.exe *.mat
run:
# UNIX uses LD_LIBRARY_PATH to find libs at runtime, Windows/MinGW uses PATH
#PATH=${MATLABROOT}/bin/win32:"${PATH}" ./matcreat
I suspect that the Matlab library will have been compiled with MSVC and since you say you are compiling your own code with MingW I would imagine the two are incompatible.
Have a look at the MingW page on mixing compilers for more information.
I am a newby in QT and cannot even get a starting example to work. The problem is that even QtCore is not found. Think something wrong with my path or not the right version is used?
#include <QtCore>
#include <iostream>
#include <QtXml/QXmlSimpleReader>
int main(int argc, char *argv[])
{
QDir xmldir("/xxx/xxx");
QXmlSimpleReader xmlReader;
}
Example of error is:
/Users/frank/xxx-build-desktop/../xxx/main.cpp:1: error: QtCore: No such file or directory.
Checked the path and the path to qmake is /usr/bin/qmake
If I run qmake -v this is printed:
QMake version 2.01a
Using Qt version 4.7.0 in /Library/Frameworks
I am using Mac 10.6.6
Any reply will be appreciated.
Here is the project file:
QT += core gui
QT += xml
QT += webkit
QT += xmlpatterns
TARGET = xxx
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp
Results from make:
iMac:~/xxx/ qmake -spec macx-g++
iMac:~/xxx/ ls -ltr
total 56
-rw-rw---- 1 frank staff 349 Feb 5 16:06 xxx.pro
-rw-rw---- 1 frank staff 3875 Feb 6 12:56 main.cpp
-rw-rw---- 1 frank staff 7985 Feb 6 12:56 xxx.pro.user
-rw-rw---- 1 frank staff 8974 Feb 6 12:56 Makefile
iMac:~/xxx/ make
g++ -c -pipe -g -gdwarf-2 -Wall -W -DQT_WEBKIT_LIB -DQT_XMLPATTERNS_LIB -DQT_XML_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/local/Qt4.7/mkspecs/macx-g++ -I. -I. -I/usr/include/QtCore -I. -I/usr/include/QtGui -I. -I/usr/include/QtXml -I. -I/usr/include/QtXmlPatterns -I. -I/usr/include/QtWebKit -I/usr/include -I. -F/Library/Frameworks -o main.o main.cpp
main.cpp:1:18: error: QtCore: No such file or directory
main.cpp: In function ‘int main(int, char**)’:
main.cpp:27: error: ‘QDir’ was not declared in this scope
main.cpp:27: error: expected `;' before ‘xmldir’
main.cpp:28: error: ‘xmldir’ was not declared in this scope
main.cpp:28: error: ‘QDir’ is not a class or namespace
main.cpp:28: error: ‘QDir’ is not a class or namespace
main.cpp:28: error: ‘QDir’ is not a class or namespace
main.cpp: At global scope:
main.cpp:25: warning: unused parameter ‘argc’
main.cpp:25: warning: unused parameter ‘argv’
main.cpp:63: warning: unused parameter ‘namespaceURI’
main.cpp:63: warning: unused parameter ‘localName’
main.cpp:63: warning: unused parameter ‘qName’
main.cpp:67: warning: unused parameter ‘namespaceURI’
main.cpp:67: warning: unused parameter ‘localName’
make: *** [main.o] Error 1
iMac:~/xxx/
For most C++ Qt applications you write, it's not immediately obvious how to compile the application by hand. This is complicated by a number of factors:
The header files may be placed in different directories depending on their version
moc, the meta-object compiler, needs to be run
The correct version of the DLLs need to be included
A number of preprocessor defines need to be in place
Given all of the above, it's easiest to use a build system like qmake, which is native to Qt, cmake, or some other build system that is Qt aware.
For people new to Qt, I recommend qmake.
Here's the basic command line usage. Qmake provides integration with both Visual Studio and XCode, but I won't address that here:
Create a directory for your project
Write whatever files you believe you need
Build a project file for qmake by running qmake on your project as follows: qmake -project "CONFIG+=xml". Since you're on mac, you might also want a -macx option, but I've never used it myself. At least in the past, qmake was not smart enough to pick up the XML dependency, so the "CONFIG+=xml" option adds it explicitly.
Create the makefiles from the project file by running qmake again: qmake
Now that you have makefiles, build the application using make, nmake, gmake, or the corresponding version of make for your system.
If everything has been picked up correctly by qmake, you should now be able to build your application by using make.
When you add new files to your project, they will need to be added to your project file (*.pro) and then qmake rerun without any options.
#includes are for header files. QtCore isn't a header, it's a directory that contains headers.
Since you're using QDir, change the first line to this:
#include <QtCore/QDir>
It is rather strange that your /usr/include/* directores don't exist. It seems that there is something wrong with the Qt installation. I don't understand Mac specifics, but from what I've been able to find out, it looks like the -F/Library/Frameworks parameter that make passes to G++ should allow you to use #include <QtCore/QtCore> instead of just #include <QtCore>. In a correct Qt installation on other platforms (Windows, Linux), both forms are equally acceptable though. But judging by the fact that G++ doesn't complain about the #include <QtXml/QXmlSimpleReader> line, the form #include <QtModule/ModuleHeader> works fine in your setup, so it could be used as a workaround, provided that there are no other problems.
Note that I wouldn't recommend to include QtCore in any form, though. It includes a lot of stuff most of which is probably useless to you and it will only increase compilation time and the probability of name conflicts. Include only what you intend to use instead, like #include <QDir> or #include <QtCore/QDir> in your case.
If you are new to Qt, and there's not special build requirement (PPC, 10.4, etc), I would strongly recommend that you download prepackaged Qt SDK of your platform. And use the included IDE, Qt Creator, to start. That will get your feet wet quickly and less painfully.
The variable settings you provided, which seems to be in your makefile, should actually be in a QMake file xxx.pro. You then run qmake, which generates the Makefile from xxx.pro, and then finally can run make. QMake uses variables such as QT and SOURCES, along with its knowledge of Qt and your installation, to produce a correct makefile.
If you do not find QtCore in /usr/include/, then this is an installation issue. In 4.7.0 I heard people having the same problem, so I guess there is a packaging problem for macs in 4.7.0.
Try to get 4.7.1 or build your own out of the sources.