cmake: fix problem that go_library is never rebuilt. #2954
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`merge_static_libs` also have the similar logic of using ${dummyfile},
I am not sure if there needs a change or not.
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| # This custom command will always run since it depends on a not | ||
| # existing file. | ||
| add_custom_command( |
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Naive question: why add a custom command since we already have file(WRITE ${dummyfile} "const char * dummy = \"${dummyfile}\";") below?
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From my understanding file will create a file when cmake is called, during the Makefile generation process. But it will never be called when make is called. This has the problem that after the first time building, go_library never gets build again even the source code changed.
In contrast, the custom command is called when make is called, forcing the rebuild.
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I see. Thanks! No rebuild is due to we build go libs by add_custom_command , so make will not track the source file changes.
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| # This custom command will always run since it depends on a not | ||
| # existing file. | ||
| add_custom_command( |
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I see. Thanks! No rebuild is due to we build go libs by add_custom_command , so make will not track the source file changes.
| # existing file. | ||
| add_custom_command( | ||
| OUTPUT dummy_rebulid_${TARGET_NAME} | ||
| COMMAND cmake -E touch ${dummyfile} |
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Is that being built every time? Even if there no changes?
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Yes. I thought it's better to rebuild even there is no change than not rebuild when there is change.
It's hard to track if the library source to be built changed or not, since the files may depend on other files that have changed located in other directories.
The good news is Go compiler caches the build result for all dependencies when they have not changed.
merge_static_libsalso have the similar logic of using${dummyfile},I am not sure if there needs a change or not.