feat: support CMake 3.27 and up for building C++20 module #356
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@ChuanqiXu9 hi Chuanqi, could you please help review this change? |
CMake 3.27 changed the `CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API`
for enabling the experimental C++ module support back then. and
CMake 3.28 officially support C++20 modules. so let's set
the `CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API` and set the policy
accordingly.
without this change, following steps fail the build
```console
$ CC=clang CXX=clang++ cmake -Bbuild_modules -DCMAKE_BUILD_TYPE=Release -DASYNC_SIMPLE_BUILD_MODULES=ON -GNinja
$ ninja -C build_modules/
ninja: Entering directory `build_modules/'
[29/73] Building CXX object demo_example/CMakeFiles/CountCharUsingModules.dir/CountChar.cpp.o
FAILED: demo_example/CMakeFiles/CountCharUsingModules.dir/CountChar.cpp.o
/home/kefu/.local/bin/clang++ -DUSE_MODULES -I/tmp/async_simple/demo_example/asio -I/tmp/async_simple/modules/.. -std=c++20 -D_GLIBCXX_USE_CXX11_ABI=1 -Wno-deprecated-register -Wno-mismatched-new-delete -Wno-deprecated-declarations -D_FILE_OFFSET_BITS=64 -fPIC -Wall -Werror -D__STDC_LIMIT_MACROS -g -Wno-uninitialized -m64 -DTARGET_64 -O2 -DNDEBUG -std=c++20 -MD -MT demo_example/CMakeFiles/CountCharUsingModules.dir/CountChar.cpp.o -MF demo_example/CMakeFiles/CountCharUsingModules.dir/CountChar.cpp.o.d -o demo_example/CMakeFiles/CountCharUsingModules.dir/CountChar.cpp.o -c /tmp/async_simple/demo_example/CountChar.cpp
/tmp/async_simple/demo_example/CountChar.cpp:22:8: fatal error: module 'async_simple' not found
22 | import async_simple;
| ~~~~~~~^~~~~~~~~~~~
1 error generated.
```
with CMake 3.28.20231228-g158ecdc and Clang 18 (64e63888dd8beae7272c0526e4770e31857dd0e7).
see also https://cmake.org/cmake/help/latest/policy/CMP0155.html
Signed-off-by: Kefu Chai <[email protected]>
tchaikov
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CMake 3.27 changed the
CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_APIfor enabling the experimental C++ module support back then. and CMake 3.28 officially support C++20 modules. so let's set theCMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_APIand set the policy accordingly.without this change, following steps fail the build
with CMake 3.28.20231228-g158ecdc and Clang 18 (64e63888dd8beae7272c0526e4770e31857dd0e7).
see also https://cmake.org/cmake/help/latest/policy/CMP0155.html
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