From d2d6eba16a8ff2057384abd2c0ff70ac6862513a Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.a.alekhin@gmail.com>
Date: Sat, 13 Feb 2021 00:35:18 +0000
Subject: [PATCH] cmake: fix add_apple_compiler_options() calls and OBJCXX
 handling

---
 cmake/OpenCVUtils.cmake          | 10 ++++++++--
 modules/highgui/CMakeLists.txt   |  2 +-
 modules/imgcodecs/CMakeLists.txt |  2 +-
 modules/videoio/CMakeLists.txt   |  2 +-
 4 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/cmake/OpenCVUtils.cmake b/cmake/OpenCVUtils.cmake
index 735fa10a4c..d03dc9c551 100644
--- a/cmake/OpenCVUtils.cmake
+++ b/cmake/OpenCVUtils.cmake
@@ -564,7 +564,11 @@ macro(ocv_check_flag_support lang flag varname base_options)
   elseif("_${lang}_" MATCHES "_C_")
     set(_lang C)
   elseif("_${lang}_" MATCHES "_OBJCXX_")
-    set(_lang OBJCXX)
+    if(DEFINED CMAKE_OBJCXX_COMPILER)  # CMake 3.16+ and enable_language(OBJCXX) call are required
+      set(_lang OBJCXX)
+    else()
+      set(_lang CXX)
+    endif()
   else()
     set(_lang ${lang})
   endif()
@@ -573,7 +577,9 @@ macro(ocv_check_flag_support lang flag varname base_options)
   string(REGEX REPLACE "^(/|-)" "HAVE_${_lang}_" ${varname} "${${varname}}")
   string(REGEX REPLACE " -|-|=| |\\.|," "_" ${varname} "${${varname}}")
 
-  ocv_check_compiler_flag("${_lang}" "${base_options} ${flag}" ${${varname}} ${ARGN})
+  if(DEFINED CMAKE_${_lang}_COMPILER)
+    ocv_check_compiler_flag("${_lang}" "${base_options} ${flag}" ${${varname}} ${ARGN})
+  endif()
 endmacro()
 
 macro(ocv_check_runtime_flag flag result)
diff --git a/modules/highgui/CMakeLists.txt b/modules/highgui/CMakeLists.txt
index bd7c8980be..296f4cab2b 100644
--- a/modules/highgui/CMakeLists.txt
+++ b/modules/highgui/CMakeLists.txt
@@ -151,7 +151,7 @@ ocv_create_module(${HIGHGUI_LIBRARIES})
 
 macro(ocv_highgui_configure_target)
 if(APPLE)
-  add_apple_compiler_options(the_module)
+  add_apple_compiler_options(${the_module})
 endif()
 
 if(MSVC)
diff --git a/modules/imgcodecs/CMakeLists.txt b/modules/imgcodecs/CMakeLists.txt
index 1b832eaa3a..2498b5ae83 100644
--- a/modules/imgcodecs/CMakeLists.txt
+++ b/modules/imgcodecs/CMakeLists.txt
@@ -131,7 +131,7 @@ ocv_create_module(${GRFMT_LIBS} ${IMGCODECS_LIBRARIES})
 
 macro(ocv_imgcodecs_configure_target)
 if(APPLE)
-  add_apple_compiler_options(the_module)
+  add_apple_compiler_options(${the_module})
 endif()
 
 if(MSVC)
diff --git a/modules/videoio/CMakeLists.txt b/modules/videoio/CMakeLists.txt
index 3dac3e816c..cc0c5eb1c5 100644
--- a/modules/videoio/CMakeLists.txt
+++ b/modules/videoio/CMakeLists.txt
@@ -253,7 +253,7 @@ ocv_create_module(${VIDEOIO_LIBRARIES})
 
 macro(ocv_videoio_configure_target)
 if(APPLE)
-  add_apple_compiler_options(the_module)
+  add_apple_compiler_options(${the_module})
 endif()
 
 if(MSVC)