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macOS: compile Objective-C sources with clang when building with GCC #3073

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macOS: compile Objective-C sources with clang when building with GCC #3073

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24 changes: 24 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,30 @@ else (APPLE)
set(MACOSX_BUNDLE FALSE)
endif (APPLE)

# Objective-C / Objective-C++ are needed for some macOS platform integration
# (e.g. Metal presentation glue in the renderer). GCC on macOS cannot target
# Apple's Objective-C runtime, so when the engine is built with GCC we route
# .m / .mm sources to clang while everything else keeps building with GCC.
# CMake selects the compiler per source language (.m -> OBJC, .mm -> OBJCXX)
# and links libc++ for such targets automatically, so no per-file or
# per-target handling is required. Objective-C sources used this way must keep
# an extern "C" boundary: clang compiles them against libc++, so no C++
# standard-library types may cross to the libstdc++ side of the engine.
if (APPLE)
if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
find_program(OBJC_CLANG NAMES clang)
find_program(OBJCXX_CLANG NAMES clang++)
if (NOT OBJC_CLANG OR NOT OBJCXX_CLANG)
message(FATAL_ERROR "Building on macOS with GCC requires clang/clang++ for Objective-C sources, but they were not found")
endif ()
set(CMAKE_OBJC_COMPILER "${OBJC_CLANG}")
set(CMAKE_OBJCXX_COMPILER "${OBJCXX_CLANG}")
message(STATUS "macOS: compiling Objective-C/C++ with clang (${OBJCXX_CLANG}); C/C++ use ${CMAKE_CXX_COMPILER}")
endif ()
enable_language(OBJC)
enable_language(OBJCXX)
endif (APPLE)

### Compiler flags and defines based on build type
include(TestCXXFlags)

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