System Information

OpenCV version: 4.x ( 3e43d0c )
Operating System / Platform: Ubuntu 24.04
Compiler & compiler version: GCC 13.3.0

Detailed description

C++ standard checker does not work with C++11 supported compiler .

HAVE_CXX11 is detected with CMAKE_CXX11_COMPILE_FEATURES.

CMAKE_CXX11_COMPILER_FEATURES means what features are supported the compiler. It doesnot means what features are available with this configuration.

See https://cmake.org/cmake/help/v3.31/manual/cmake-compile-features.7.html#manual:cmake-compile-features(7)

The CMAKE_C_COMPILE_FEATURES, CMAKE_CUDA_COMPILE_FEATURES , and CMAKE_CXX_COMPILE_FEATURES variables contain all features CMake knows are known to the compiler, regardless of language standard or compile flags needed to use them.

So if cmake -DCMAKE_CXX_STANDARD=98 runs with C++11 supported compiler, HAVE_CXX11 is ON.
Following C++ standard check will passed always for C++11 supported compiler.

Steps to reproduce

cmake -S opencv4 -B build4-main.CXX98 -DCMAKE_CXX_STANDARD=98 -GNinja

This cmake command finished without any error.

-- General configuration for OpenCV 4.12.0-dev =====================================
--   Version control:               4.11.0-264-g3e43d0cfca

--   C/C++:
--     Built as dynamic libs?:      YES
--     C++ standard:                98
--     C++ Compiler:                /usr/bin/c++  (ver 13.3.0)

-- -----------------------------------------------------------------
--
-- Configuring done (32.0s)
-- Generating done (0.3s)
-- Build files have been written to: /home/kmtr/work/build4-main.CXX98

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)