OpenCV 2.4.3+ with libstdc++ for iOS? - c++

I'm trying to include a recent version of OpenCV into an existing iOS project and am having linker errors because my XCode project is set to use libstdc++ and not libc++ / C++ 11 support.
I have seen several other people who have fixed their errors by enabling libc++. Examples:
Linker errors after upgrading Xcode to 4.5.2 and OpenCV to 2.4.3
How to resolve iOS Link errors with OpenCV
However, I NEED to use libstdc++ because I have other 3rd party libraries which are already compiled with the older stdlib (can't be changed). Is there a way to compile OpenCV 2.4.3+ without -stdlib=libc++ ? Are there special flags to pass to CMake? or to the build_framework.py script that comes in the ios folder of the OpenCV source code?
Alternatively, does anyone have a binary version available? It seems all downloadable from OpenCV assume libc++ / C++11.

In the source for openCV locate this file:
ios/cmake/Modules/Platform/iOS.cmake
Change this line:
set (CMAKE_CXX_FLAGS "-stdlib=libc++ -headerpad_max_install_names -fvisibility=hidden -fvisibility-inlines-hidden")
to:
set (CMAKE_CXX_FLAGS "-stdlib=libstdc++ -headerpad_max_install_names -fvisibility=hidden -fvisibility-inlines-hidden")
Compile using the python script
ios/build_framework.py
Then you should be good to go
I have just tried this on 2.4.3 source, swapped in the resulting framework on an existing project, changed the C++ standard library for the project to libstdc++ and it runs fine.

I am also working on a project using OpenCV and a 3rd party library which requires libstdc++.
As I just ran into this problem myself, I wanted to share what worked for me.
I was able to get OpenCV working by adding "libc++.dylib" to my project.
Build Phases -> "Link Binary with Libraries" -> "+" -> libc++.dylib
For reference, I am using OpenCV 2.4.9 (opencv-2.4.9) from opencv.org. I compiled it using the ios platform build_framework.py per the instructions in OpenCV's docs. No modification necessary.

Related

Using SFML for Codeblocks C++ appears ERROR library SFML

I have a problem when I tried to install SFML on Codeblocks. Well, first I install codeblocks: codeblocks-20.03mingw-setup.exe . That's compile correctly after that I download SFML 2.5.1: GCC 5.1.0 TDM (SJLJ) - Code::Blocks - 32-bit.
Following, I extract the SFML file.The problem comes I COPY THE CONTENT OF "BIN" INSIDE OF MY CODEBLOCKS PROJECT. A video helps me to do all of before, I WROTE ALL THE LIBRARIES: GRAPHICS, WINDOW, NETWORK, AUDIO, SYSTEM BUT NOTHING. I show you the error:
cannot find -lsfml-audio-d-2
And continue with network, window,system, graphics
At the ends:
error: ld returned 1 exit status
what's wrong? help me please. I have to make a video game using CODEBLOCKS as soon as I fixed this problem. I'll so thankful for your answers.
On the SFML download website (https://www.sfml-dev.org/download/sfml/2.5.1/), it says:
The compiler versions have to match 100%!
The CodeBlocks 20.03 MinGW installation includes version 8.1.0 of the GCC compiler (as is stated on the download page: http://www.codeblocks.org/downloads/26).
Your downloaded version of SFML thus is only intended to work with version 5.1.0 of GCC, but you have version 8.1.0. This can result in a number of errors.
There are a few possibilities to fix your issue:
You could theoretically compile SFML yourself with your specific compiler, but this option may be quite complicated.
You could use a compiler with the matching version. On the SFML download website, there are some links to the needed compilers. After having installed a compiler, you will have to configure CodeBlocks to detect the new compiler on your system (reference: Adding compiler to code::blocks). Now, in order to add SFML to your project, I would suggest to use this official guide:
https://www.sfml-dev.org/tutorials/2.5/start-cb.php
You could use an environment like MSYS2 (which I use personally) to have a package manager to manage your compiler and libraries installations. This way, your compiler installation and your libraries should work with each other. But in order to use this compiler in CodeBlocks, CodeBlocks would have to be configured.
I would suggest that you refer to option 2 because it probably is the quickest solution.
Feel free to ask if you have any more questions. I know from personal experience that setting up SFML (or any other C++ library) to work with your IDE may be quite tricky.

Make - Internal compiler Error under QT 5.14.2 "Q_CORE_EXPORT"

I just installed QT Creator with QT under Win10 to build an already existing project. (Under Ubuntu everything went fine running the Make file). I'm not an expert for QT therefore I'm not able to find out how to resolve the error:
C:\Qt\5.14.2\mingw73_64\include/QtCore/qfloat16.h:102:54: internal compiler error: in make_rtl_for_nonlocal_decl, at cp/decl.c:6590
Q_CORE_EXPORT static const quint32 mantissatable[];
My gcc version is 8.3.0 (x86_64-posix-seh, Built by strawberryperl.com project). Is there something missing or broken in the installation?
On windows, you generally need to have a Qt which was built with the same (or compatible, but that can be hard to verify) compiler and relevant build options, as what you are using to build your application.
I doubt you will find a pre-built Qt SDK for that version of gcc, so if you want to use it, you should build Qt from sources. It can be a bit tedious on Windows, there are a fewf prerequisites you have to get etc. I recommend you use the Qt online installer to install a MinGW version of Qt SDK, and matching version of MinGW (also offered by the Qt installer.
I just found out from qmake.stash, that the included script for creating the make file always referenced a false path for the gcc compiler. I therefore build i manually with the QT Creator and it worked as expected. So I guess the fault was due to different paths for gcc in the environmental variables.
Here is the bug, there is a link to the patch: https://github.com/msys2/MINGW-packages/issues/5006
Also you can just downgrade to mingw gcc 8.2.0

OpenCV Qt Setup with MS Visual C++ 2012 Compiler

Like the title says, I have been using Qt creator along with a kit that uses the Visual C++ 12.0 (x86_amd64) compiler and I have been trying to get openCV set up so that I can use that library in my project. I downloaded the most recent version of openCV (alpha 3.0.0) and have tried numerous ways of trying to link it to QT, but no matter what I try it fails.
I have tried looking at several tutorials that have been using Cmake to compile the source into binaries, but those have also failed. Since I am using the C++ 12 compiler, is it possible to just use the pre-compiled binaries that come with the download, or do I have to manually compile them? I downloaded it from the OpenCV site and tried to use cmake to compile the binaries, configured with the visual C++ 2012 compiler, but I have no idea where to go after those binaries are generated so that's why I have tried with the binaries you download straight from the site.
Any thoughts or links to tutorials are greatly appreciated, I just can't get this thing to work.
A few things I have tried have been adding
INCLUDEPATH += "C:\OpenCV-3.0.0\opencv\sources\include"
To link to cv.h, and I have these libraries linked because I tried linking all the ones I found in the pre compiled binaries
LIBS += "C:\OpenCV-3.0.0\opencv\build\x86\vc12\lib\opencv_ts300.lib"
"C:\OpenCV-3.0.0\opencv\build\x86\vc12\lib\opencv_ts300d.lib"
"C:\OpenCV-3.0.0\opencv\build\x86\vc12\lib\opencv_world300.lib"
"C:\OpenCV-3.0.0\opencv\build\x86\vc12\lib\opencv_world300d.lib"

How do I set up OpenCV for MinGW project?

I regularly use Code::Blocks and MinGW for my C/C++ projects. I would like to be able to use OpenCV, since it has a nice library for computer vision projects. They have dropped support for MinGW. I have heard you can build it on your own somehow, but I have no experience doing this with 3rd party libraries. Can someone explain how to build it in a simple way for MinGW?
There is, or at least there was at least until 2.4.6, precompiled version of opencv that works out of the box with mingw as long as you use the dw2(standard) version of mingw.
since i needed sjlj support i had to build my own version of openCV 2.4.6
I did he following - i am pretty sure it will work for the current openCV version as well
Setup your preferred Mingw Environment - i would strongly recommend to use gcc 4.5 or newer
Intstall Msys
Intall Cmake - you can get a binary package
Start the Cmake GUI
Select the openCV source folder
Click Configure and select MSYS-Makfiles
Errors in the first run of Configure might be resolved if you run Configure again
Click Generate
use MSYS make to run the generated makefile
Copy all desired libraries and include files to your mingw-installation or your project

build problems with Qt and opencv on Windows

I would like to create a gui application with Qt, using opencv on Windows XP. I used both Qt and opencv before, but never together. Long story short, I'm unable to get opencv work with Qt.
As on all the forums I searched there are just little pieces of information scattered around, usually with no answer, I summarize here all the steps I've taken.
Downloaded the Qt SDK (4.6.3) for Windows, and used it for some time, successfully.
Downloaded the opencv 2.3.1 megapack for Windows, complete with binaries. I managed to compile my Qt project including opencv successfully, but any opencv function call resulted in a crash. I read on some forums that the binaries in the Windows megapack don't support Qt, and I have to build opencv myself
I downloaded the latest version of CMake (2.8).
I downloaded the source of opencv from here: http://code.opencv.org/svn/opencv/branches/2.3/
I downloaded the source for the version of Qt I had (4.6.3)
I found my old version of visual Studio 2005
I created a VS2005 project with CMake, checking the support for Qt. (WITH_QT checked)
I built opencv in VS2005. It created most of the libraries, but not all. Highgui was among the failed ones. The problem: Qt\4.6.3\src\corelib\global\qconfig.h was not found. There was no qconfig.h at all in the source I downloaded! I found some templates qconfig-large.h, qconfig-small.h etc., so I renamed one of them to qconfig.h. Now I got a screen full of linker errors.
I downloaded the latest Qt source instead (4.8.1). Now there is a source file qbenchmark.h that includes QtTest/qbenchmarkmetric.h which cannot be found.
I gave up, and tried MinGW.
I downloaded the latest MinGW (2011.11.18)
I set CMake to generate a MinGW makefile, but I got the following error:
.
CMake Error at C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/Platform/Windows-g++.cmake:1 (INCLUDE):
include could not find load file:
C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/Platform/Windows-gcc.cmake
Call Stack (most recent call first):
C:/Program Files/CMake 2.8/share/cmake-2.8/Modules/CMakeCXXInformation.cmake:59 (INCLUDE)
True, there is a Windows-g++.cmake file in the Modules/Platform directory, but it references Windows-gcc.cmake which does not exist!
Is there anyone who managed to build opencv with Qt support on Windows, and if yes, how?
Edit:
The problem is definitely with the Qt source. I managed to generate a MinGW makefile, and the build went all OK until it stopped in src/testlib/qtestsystem.h because there was an include for QtCore/qelapsedtimer.h which file is in a completely different directory! Does Qt release incomplete sources, or did I do something wrong?
Edit2
My torment continues. I cleaned everything and started anew. This time without even trying Visual Studio.
I downloaded the latest Qt libs with source (4.8.1)
I downloaded the latest MinGW (2011.11.18)
With CMake I successfully created a Makefile, and built it with MinGW. I got some shiny new libs (libopencv_core231, etv.). I was very happy, but how wrong I was to celebrate that soon!!
I downloaded the latest Qt SDK (strangely, it was 4.8.0, so I set Qt Creator to use the 4.8.1) and created a test program without opencv to see if it works. It worked!
I tried using opencv, just reading and displaying an image. It didn't work. exited with code -1073741511
I tried running the .exe directly, outside of Qt Creator. It complained of a missing libstdc++-6.dll
I did a search for it, and found on in my MinGW install (c:\mingw\bin, 958 KB), and one in my Qt install (c:\qt\mingw\bin, 793 KB) - this mingw came bundled with Qt.
I tried both, by copying them in the same folder where my .exe is, but neither worked. I got "The procedure entry point _ZNSt9exceptionD2Ev could not be located in the dynamic link library libstdc++-6.dll." with both. This was in debug, so I tried release, and I got a similar error, with some other entry point not found.
I searched the forums, and I found suggestions that I should link libstdc++ statically. I inserted -static-libgcc -static-libstdc++ at the lines QMAKE_LFLAGS = and QMAKE_LFLAGS_DEBUG = in the file c:\Qt\mkspecs\win32-g++\qmake.conf. This had no effect at all, even after restarting Qt Creator and rebuilding. If I don't copy the libstdc++-6.dll, it still requires it.
Of course, my simple test program without opencv runs from the exe without needing any libstdc++-6.dll, so that means my opencv build is responsible? I wanted to build opencv anew, but I cannot find any CMake settings referring to libstdc++ !
It might be a clue:
When using one of the libstdc++-6.dll files, the error about a missing entrypoint mentions QtGui4.dll. I have a debug build, so it should be QtGui*d*4.dll, shouldn't it? Are there different libstdc++s for debug and release? Either way, I tried to build release, but it didn't work either, same error
Is there no single person on this planet who tried using Qt with QtCreator and opencv 2.3 together on Windows xp, and succeeded? From searching all the forums and Qt archives, I could not find anyone. I'm ready to do the development in Linux, but I'll need a Windows release sooner or later anyway.
I'm trying to resist the temptation of the dark side, which whispers into my ears to forget Qt, MinGW, g++, opencv and try to hack together something in Visual Basic. Oh, the horrors!
Just FYI, I went basically through the same nightmare of combining Qt and OpenCV. This was my experience:
I downloaded the Qt SDK 4.7.4 with Qt Creator 2.4.1 and installed it, no problem.
I downloaded and installed OpenCV 2.4.2 and not knowing that it already came with MinGW...
I downloaded the MinGW compiler which of course had a different version than the one which came already with Qt
This completely messed up my CMake, even when I explicitly told CMake to use the Qt gcc.exe and g++.exe it also used some stuff from my freshly installed MinGW. Probably because I eagerly added every directory to my PATH variable. What a fool I was!
CMake was not able to generate any useful files, so I gave up and installed the OpenCV superpack, hoping this would make things easier.
6.I spent hours wondering, why Qt and OpenCV from the superpack didnt work properly together. I never quite understood. I had the same errors that other users describe here, like console programs crashing as soon as some OpenCV was included. The strange thing is, that I could start the executable manually from FileExplorer (I added all .dlls you could think of to the project folder: opencv_core242.dll, opencv_highgui242.dll, QtCore4.dll, QtGui4.dll and so on...) BUT I could not launch my little test program from within the Qt Creator environment.
I analysed if there was a problem with my DLLs using depends.exe and found out that even though I configured everything to be in DEBUG using the MinGW compiler, my program still tried to use QtCore4.dll and not QtCore4d.dll... So my best guess was, that it was mixing debug and release version.
I gave up using the superpack and again tried to use CMAKE first and then build OpenCV using the Qt MinGW version AND making sure to setup everything for Debug mode and enable the QT option. But no luck with that so far
I stopped using MinGW and switched over to MSVC2010, which works better. However I am still not able to debug the program since the MSVC2010 debugger engine seems to be missing. I dont really know how to manually add this but I am still working on it
So what I can definitely tell is that using Qt and OpenCV for somebody who has little experience is far from trivial!
You should build OpenCV from source, as you already did, it is no hassle. Note that recent versions of OpenCV can be built with and w/o Qt. Highgui optionally uses Qt! It is your choice if you build with or without Qt.
I used Qt libraries together with OpenCV for long time now. I never went for the SDK, instead I used the libs which are built for corresponding VS version. See here: http://qt.nokia.com/downloads/downloads#qt-lib
You can have it for VS2008 and VS2010, but earlier versions are also available built for VS2005. Old versions of Visual Studio suck so hard, why use them anyway.
Then I never had problems pulling it together in a CMake project. It goes along the lines of:
find_package(OpenCV)
find_package(Qt4 ${VOLE_MINIMUM_QT_VERSION} COMPONENTS QtCore QtGui)
find_package(Qt4 ${VOLE_MINIMUM_QT_VERSION} COMPONENTS QtOpenGL)
...
qt4_wrap_cpp(moc_sources ${vole_module_moc_sources})
qt4_wrap_ui(uic_sources ${vole_module_ui_sources})
qt4_add_resources(rcc_sources ${vole_module_rcc_sources})
You know, the usual stuff.
Five man weeks later you may probably get it run under Windows, while under GNU/Linux it is three commands in the shell.
You might have an easier time configuring Qt Creator with OpenCV. This post shows how to achieve that, step-by-step! It displays several screenshots to aid in the process too.