MinGW >> OpenCV
解決"error: recursive_mutex in namespace std does not name a type"問題
參考資訊：
1. issues
2. c-mutex-in-namespace-std-does-not-name-a-type
問題如下：
In file included from opencv-4.3.0/modules/core/src/precomp.hpp:49:0,
from opencv-4.3.0/modules/core/src/algorithm.cpp:43:
opencv-4.3.0/modules/core/include/opencv2/core/utility.hpp:714:14: error: ‘recursive_mutex’ in namespace ‘std’ does not name a type
typedef std::recursive_mutex Mutex;
^~~~~~~~~~~~~~~
opencv-4.3.0/modules/core/include/opencv2/core/utility.hpp:715:25: error: ‘Mutex’ is not a member of ‘cv’
typedef std::lock_guard<cv::Mutex> AutoLock;
^~
opencv-4.3.0/modules/core/include/opencv2/core/utility.hpp:715:25: error: ‘Mutex’ is not a member of ‘cv’
opencv-4.3.0/modules/core/include/opencv2/core/utility.hpp:715:34: error: template argument 1 is invalid
typedef std::lock_guard<cv::Mutex> AutoLock;
^
In file included from opencv-4.3.0/modules/core/src/algorithm.cpp:43:0:
opencv-4.3.0/modules/core/src/precomp.hpp:365:5: error: ‘Mutex’ in namespace ‘cv’ does not name a type
cv::Mutex&& getInitializationMutex();
^~~~~
modules/core/CMakeFiles/opencv_core.dir/build.make:109: recipe for target 'modules/core/CMakeFiles/opencv_core.dir/src/algorithm.cpp.o' failed
make[2]: *** [modules/core/CMakeFiles/opencv_core.dir/src/algorithm.cpp.o] Error 1
CMakeFiles/Makefile2:1839: recipe for target 'modules/core/CMakeFiles/opencv_core.dir/all' failed
make[1]: *** [modules/core/CMakeFiles/opencv_core.dir/all] Error 2
Makefile:182: recipe for target 'all' failed
make: *** [all] Error 2
解法如下(執行如下命令切換成支援posix的編譯器)：
$ sudo update-alternatives --config x86_64-w64-mingw32-gcc
There are 2 choices for the alternative x86_64-w64-mingw32-gcc (providing /usr/bin/x86_64-w64-mingw32-gcc).
Selection Path Priority Status
------------------------------------------------------------
0 /usr/bin/x86_64-w64-mingw32-gcc-win32 60 auto mode
* 1 /usr/bin/x86_64-w64-mingw32-gcc-posix 30 manual mode
2 /usr/bin/x86_64-w64-mingw32-gcc-win32 60 manual mode
Press <enter> to keep the current choice[*], or type selection number:
$ sudo update-alternatives --config x86_64-w64-mingw32-g++
There are 2 choices for the alternative x86_64-w64-mingw32-g++ (providing /usr/bin/x86_64-w64-mingw32-g++).
Selection Path Priority Status
------------------------------------------------------------
0 /usr/bin/x86_64-w64-mingw32-g++-win32 60 auto mode
* 1 /usr/bin/x86_64-w64-mingw32-g++-posix 30 manual mode
2 /usr/bin/x86_64-w64-mingw32-g++-win32 60 manual mode
Press <enter> to keep the current choice[*], or type selection number: