Better support for CMake: TestBigEndian, CheckTypeSize, CMAKE_CROSSCOMPILING_EMULATOR #3447
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Make libraries, especially scientific libraries, use the TEST_BIG_ENDIAN CMake function to determine the endianness of the target system. Internally, this uses 'file(STRINGS' on file compiled for the target system that has static variables. Usually, the compiled binary will reveal its endianess, but emscripten does produces javascript or html instead of binaries. Override TEST_BIG_ENDIAN and always return 0.
| @@ -258,3 +258,14 @@ if ("${CMAKE_GENERATOR}" MATCHES "^Visual Studio.*") | |||
| set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${EMSCRIPTEN_VS_LINKER_FLAGS}" CACHE STRING "") | |||
| set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${EMSCRIPTEN_VS_LINKER_FLAGS}" CACHE STRING "") | |||
| endif() | |||
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| if (NOT DEFINED CMAKE_CROSSCOMPILING_EMULATOR) | |||
| find_program(node_js_executable NAMES node nodejs) | |||
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Would this be better to be NAMES nodejs node to search for the more specific name first? See e.g. #3296
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Yes, good point. I'll switch it.
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Thanks, this looks very good! One micro-comment above, but can merge either way. Let me know what you think. |
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IMHO, there is an issue with this approach of overriding common CMake modules. For a multi-platform project, these overridden modules work only for Emscripten/HTML5 platform. This will force project maintainer to configure CMake module search path differently between Emscripten platform and other platforms. A better way is to use the original CMake modules and then enhance it with |
This variable was added in recent CMake Git master. It should point to an executable that acts like an emulator for the target system when cross-compiling. For emscripten, this is nodejs. This executable is used by CMake to run executables in try_run commands. By adding support for this variable, it prevents the need to manually populate the tedious TryRunResults.cmake file. The emscripten configured path to NodeJS is added to the emcmake command. In the Emscripten.cmake file, if CMAKE_CROSSCOMPILING_EMULATOR is not defined (which is would be if using emcmake), and attempt is made to find nodejs and use it.
The CMake CheckTypeSize module is used by many projects to get sizes of types for the target platform. Its standard implementation builds a file that contains the type size with the try_compile command, then uses file(STRINGS on the built function to extract the size from the contents of the built binary. Since emscripten produces javascript and html instead of binaries, the string is not embedded directly in the 'binary' as expected. Alternatively, we use a try_run and return the size of the type in the return value.
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@weitjong Yes, eventually these fixes should be upstreamed into CMake. |
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@weitjong: The current approach is to call I don't think it's feasible to take the approach that Emscripten should not do "system" customizations to CMake, but that development should be done in upstream CMake, since especially in Linux world, people typically have very old CMakes in their systems, 2.8 seems to be quite popular, so it would be a very slow way to move forward. Having |
Better support for CMake: TestBigEndian, CheckTypeSize, CMAKE_CROSSCOMPILING_EMULATOR
…of not being able to concatenate str and list.
This overrides two CMake modules that are commonly used by projects, especially scientific projects or projects that aim to support a number of platforms.
The TestBigEndian modules is replaced. This addresses:
#1106
Also the CheckTypeSize module is replaced.
#400
The fix for CheckTypeSize involves the use of the CMake try_run command. Also ease the building of CMake project files by adding support for the CMAKE_CROSSCOMPILING_EMULATOR variable, and pointing it to nodejs. This prevents the need to manually populate CMake TryRunResults.cmake files. It currently requires CMake Git master (to be released as CMake 3.3). Everything should still work with older CMake.
New tests are added to the test suite. All tests passed when
tests/runner.py