errors on building opencv with MinGW on windows without VisualStudio

[eheperson]

System information (version)

• OpenCV => 4.2
• Operating System / Platform => Windows 10 64 Bit
• Compiler => MinGW64

Detailed description

I am trying build latest version openCV library via MinGW on Window10 64 bit machine without Microsoft Visual Studio. I know that is a little bit tricky method but I don't like use Microsoft build tools. I handled the errors I have encountered so far except latest one.

In addition, I checked out Microsoft VS Docs. That line confused me : " The _isnan and _isnanf functions are Microsoft-specific. ". I'm not sure if the method I use is wrong for my operating system. I also checked out openCV Docs and FAQ, I didn't find any solution for my problem.

The error I get is below :

[ 45%] Building CXX object modules/wechat_qrcode/CMakeFiles/opencv_wechat_qrcode.dir/src/binarizermgr.cpp.obj
In file included from D:\opencvInstall\test3\opencv_contrib\modules\wechat_qrcode\src\zxing/common/bitarray.hpp:15,
from D:\opencvInstall\test3\opencv_contrib\modules\wechat_qrcode\src\zxing/common/bytematrix.hpp:13,
from D:\opencvInstall\test3\opencv_contrib\modules\wechat_qrcode\src\imgsource.hpp:13,
from D:\opencvInstall\test3\opencv_contrib\modules\wechat_qrcode\src\precomp.hpp:25,
from D:\opencvInstall\test3\opencv_contrib\modules\wechat_qrcode\src\binarizermgr.cpp:7:
D:/opencvInstall/test3/opencv_contrib/modules/wechat_qrcode/src/zxing/zxing.hpp: In function 'bool zxing::isnan(float)':
D:/opencvInstall/test3/opencv_contrib/modules/wechat_qrcode/src/zxing/zxing.hpp:64:37: error: '_isnan' was not declared in this scope; did you mean 'isnan'?
64 | inline bool isnan(float v) { return _isnan(v) != 0; }
......|....................................................................^~~~~~
......|....................................................................isnan
D:/opencvInstall/test3/opencv_contrib/modules/wechat_qrcode/src/zxing/zxing.hpp: In function 'bool zxing::isnan(double)':
D:/opencvInstall/test3/opencv_contrib/modules/wechat_qrcode/src/zxing/zxing.hpp:65:38: error: '_isnan' was not declared in this scope; did you mean 'isnan'?
65 | inline bool isnan(double v) { return _isnan(v) != 0; }
......|....................................................................^~~~~~
......|....................................................................isnan
mingw32-make[2]: *** [modules\wechat_qrcode\CMakeFiles\opencv_wechat_qrcode.dir\build.make:82: modules/wechat_qrcode/CMakeFiles/opencv_wechat_qrcode.dir/src/binarizermgr.cpp.obj] Error 1
mingw32-make[1]: *** [CMakeFiles\Makefile2:7468: modules/wechat_qrcode/CMakeFiles/opencv_wechat_qrcode.dir/all] Error 2

That is my first issue report on github. If there is any mistake in format so sorry.

[alalek]

/cc @dddzg

Possible solutions:

• reusing cvIsNaN() from "core" module
• std::isnan() should work with MSVC too
• change #if condition in zxing.hpp:

-#if defined(_WIN32) || defined(_WIN64)
+#if defined(_MSC_VER)

@eheperson Please check which fix works with MinGW (it is not officially supported platform).

[dddzg]

@eheperson @alalek Thanks a lot. I remove _isnan and fix the bug in #2849 .

[deadprogram]

This would appear to not have corrected the issue, or perhaps it exposed a different issue. In the latest release 4.5.2 I receive the following error when building:

[ 71%] Linking CXX shared library ..\..\bin\libopencv_wechat_qrcode452.dll
C:/mingw-w64/x86_64-7.3.0-posix-seh-rt_v5-rev0/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/7.3.0/../../../../x86_64-w64-mingw32/lib/../lib/libiconv.a(localcharset.o):localcharset.c:(.text+0x63): undefined reference to `__imp_GetACP'
collect2.exe: error: ld returned 1 exit status
mingw32-make[2]: *** [modules\wechat_qrcode\CMakeFiles\opencv_wechat_qrcode.dir\build.make:976: bin/libopencv_wechat_qrcode452.dll] Error 1
mingw32-make[1]: *** [CMakeFiles\Makefile2:4547: modules/wechat_qrcode/CMakeFiles/opencv_wechat_qrcode.dir/all] Error 2

[berak]

@deadprogram
i get the same error (undefined reference to __imp_GetACP'`) using x86_64-posix-seh-rev0 8.1.0
it seems to need to link to libiconv.a

[dddzg]

A possible reason is that #define NO_ICONV and #define NO_ICONV_INSIDE are not successfully triggered. And it further leads to #include <iconv.h>. I am so sorry that I do not have the environment to reimplement the issue. Could you please check the context code about NO_ICONV and NO_ICONV_INSIDE?

[berak]

@dddzg thanks, that looks easy to fix.

what actually happens, if we disable iconv support ?
why are there 2 seperate #ifdef blocks, disabling it for android / msvc ? can we maybe collapse them to a single:

#if defined(__ANDROID_API__) || defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)

#ifndef NO_ICONV
#define NO_ICONV
#endif

#endif

(which compiles fine now, here)

[dddzg]

1. iconv is short for internationalization conversion, which is used in the original zxing-cpp codebase. So, we preserve it.
2. Yes, you can collapse them.
   PR is welcomed to fix this issue.