QT Executable under windows - qt

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.

Related

Qt requires C++11 support

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!!"

How to provide linker options when linking a static library with qmake?

I want to provide options to the linker when building a static library using qmake. Say I'd want to get verbose linker output when building with MSVC. The project file looks as follows:
# mylib.pro
TEMPLATE = lib
TARGET = mylib
CONFIG += staticlib
QT += core
win32-msvc*: QMAKE_LFLAGS += /VERBOSE
unix: QMAKE_LFLAGS += -v
That's the entire project file. It should result in an empty static library with no objects in it.
Setting neither QMAKE_LFLAGS nor QMAKE_LFLAGS_STATIC_LIB nor LIBS has any effect on the linker. Nothing set in those variables even makes it to the Makefile. If QMAKE_LFLAGS worked, I'd expect to see /VERBOSE or -v passed to the linker on the command line, as appropriate for given platform.
It doesn't matter what makefile generator is used, this behavior seems to be consistent. The two platforms of interest are.
qmake -spec win32-msvc2008
qmake -spec macx-llvm
Due to cross-platform nature of qmake, you can test it on any platform where you happen to have Qt installed. This reproduces on qmake from both Qt 4.8.4 and 5.1.1. The msvc version given in the mkspec doesn't matter.
In staticlib projects, the LFLAGS are not passed to the linker. In fact, there's no documented way to pass such flags.
The solution is generator-dependent.
For msvc_nmake, LIBFLAGS are passed to the linker instead. To get verbose output, you might add
QMAKE_LIBFLAGS += /VERBOSE
To verify that it works, on any system, you can invoke qmake -spec win32-msvc2008; the particular msvc version doesn't matter.
For unixmake, AR is used to invoke the linker, so you have to add the flags to QMAKE_AR. To get verbose output, you might add
QMAKE_AR += -v
To verify, invoke qmake -spec macx-llvm; any other unix spec should work as well.

How to use bullseye with Qt( MinGW )?

I have a project in Qt which consists of the set of projects. Projects is building via MinGW and it does not create any .cov file.
I installed bullseye and enabled coverage build but it still does not create *.con file if I try to set path variable like
C:\Program Files\BullseyeCoverage\bin;%PATH%
the build is constantly failing I always get
gcc: CreateProcess: No such file or directory
The file to build whole project is following :
d:\QtSDK\Desktop\Qt\4.7.4\mingw\bin\qmake.exe Simulator.pro -r -spec win32-g++ "CONFIG+=release"
PATH=D:\QtSDK\mingw\bin\;%PATH%
D:\QtSDK\mingw\bin\mingw32-make -f ./Makefile
How can I measure code coverage? Please help.
If somebody interested in this question - I already figured it out.
Here is a solution -
To set bullseye interceptors before your gcc compiler just replace variables
QMAKE_CC = %Bullseye gcc path%
QMAKE_CXX = %Bullseye g++ path%
This variable should be defined in *.pro file or in gcc config file, which is located in
%QTSDKPath%\Desktop\Qt\4.7.4\mingw\mkspecs\win32-g++\ // if you are using gcc from win32
You also need to set environment variable:
BULLSEYE_PATH=%PATH TO REAL COMPILER%

Linking Matlab shared library into Qt (Windows)

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.

Precompiled Headers with Qt and g++ (QtCreator)

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

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