System Information

OpenCV version: 4.x
Operating System / Platform: Ubuntu 18.04 / guix
Compiler & compiler version: GCC 13.2.0

Detailed description

I get the error displayed below when I try to build opencv with make (after running cmake).
ChatGPT told me that the fesetround & fegetround functions should not be prefixed by std:: since they are part of the C standard library (fenv.h), not the C++ standard library. After removing the std:: prefixes the error was fixed.

[ 52%] Building CXX object modules/dnn/CMakeFiles/opencv_dnn.dir/src/layers/elementwise_layers.cpp.o
cd /home/joe/Downloads/opencv-build/modules/dnn && /usr/bin/ccache /home/joe/.guix-profile/bin/c++ -DCVAPI_EXPORTS -DCV_OCL4DNN=1 -DENABLE_PLUGINS -DHAVE_FLATBUFFERS=1 -DHAVE_PROTOBUF=1 -D_USE_MATH_DEFINES -D__OPENCV_BUILD=1 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/joe/Downloads/opencv-build/3rdparty/ippicv/ippicv_lnx/icv/include -I/home/joe/Downloads/opencv-build/3rdparty/ippicv/ippicv_lnx/iw/include -I/home/joe/Downloads/opencv-4.x/modules/dnn/include -I/home/joe/Downloads/opencv-build/modules/dnn -I/home/joe/Downloads/opencv-4.x/modules/core/include -I/home/joe/Downloads/opencv-4.x/modules/imgproc/include -I/home/joe/Downloads/opencv-4.x/modules/dnn/misc/caffe -I/home/joe/Downloads/opencv-4.x/modules/dnn/misc/tensorflow -I/home/joe/Downloads/opencv-4.x/modules/dnn/misc/onnx -I/home/joe/Downloads/opencv-4.x/modules/dnn/misc/tflite -I/home/joe/Downloads/opencv-4.x/3rdparty/include/opencl/1.2 -isystem /home/joe/Downloads/opencv-build -isystem /home/joe/Downloads/opencv-4.x/3rdparty/flatbuffers/include -isystem /home/joe/Downloads/opencv-4.x/3rdparty/protobuf/src -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wundef -Winit-self -Wpointer-arith -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -Wno-deprecated -Wno-missing-declarations -Wno-shadow -Wno-unused-parameter -Wno-sign-compare -Wno-invalid-offsetof -O3 -DNDEBUG -DNDEBUG -fPIC -std=c++11 -MD -MT modules/dnn/CMakeFiles/opencv_dnn.dir/src/layers/elementwise_layers.cpp.o -MF CMakeFiles/opencv_dnn.dir/src/layers/elementwise_layers.cpp.o.d -o CMakeFiles/opencv_dnn.dir/src/layers/elementwise_layers.cpp.o -c /home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp
/home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp: In member function ‘float cv::dnn::RoundFunctor::calculate(float) const’:
/home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp:1741:43: error: ‘fegetround’ is not a member of ‘std’; did you mean ‘fegetround’?
1741 | int old_rounding_direction = std::fegetround();
| ^~~~~~~~~~
In file included from /home/joe/.guix-profile/include/c++/fenv.h:36,
from /home/joe/.guix-profile/include/c++/cfenv:41,
from /home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp:56:
/home/joe/.guix-profile/include/fenv.h:104:12: note: ‘fegetround’ declared here
104 | extern int fegetround (void) __THROW attribute_pure;
| ^~~~~~~~~~
/home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp:1742:14: error: ‘fesetround’ is not a member of ‘std’; did you mean ‘fesetround’?
1742 | std::fesetround(FE_TONEAREST);
| ^~~~~~~~~~
/home/joe/.guix-profile/include/fenv.h:107:12: note: ‘fesetround’ declared here
107 | extern int fesetround (int __rounding_direction) __THROW;
| ^~~~~~~~~~
/home/joe/Downloads/opencv-4.x/modules/dnn/src/layers/elementwise_layers.cpp:1744:14: error: ‘fesetround’ is not a member of ‘std’; did you mean ‘fesetround’?
1744 | std::fesetround(old_rounding_direction);
| ^~~~~~~~~~
/home/joe/.guix-profile/include/fenv.h:107:12: note: ‘fesetround’ declared here
107 | extern int fesetround (int __rounding_direction) __THROW;
| ^~~~~~~~~~

Steps to reproduce

make

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues, forum.opencv.org, Stack Overflow, etc and have not found any solution
• I updated to the latest OpenCV version and the issue is still there
• There is reproducer code and related data files (videos, images, onnx, etc)