forked from openkylin/platform_build
107 lines
4.8 KiB
Markdown
107 lines
4.8 KiB
Markdown
# Build System Changes for Android.mk Writers
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## Deprecating / obsoleting envsetup.sh variables in Makefiles
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It is not required to source envsetup.sh before running a build. Many scripts,
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including a majority of our automated build systems, do not do so. Make will
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transparently make every environment variable available as a make variable.
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This means that relying on environment variables only set up in envsetup.sh will
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produce different output for local users and scripted users.
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Many of these variables also include absolute path names, which we'd like to
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keep out of the generated files, so that you don't need to do a full rebuild if
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you move the source tree.
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To fix this, we're marking the variables that are set in envsetup.sh as
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deprecated in the makefiles. This will trigger a warning every time one is read
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(or written) inside Kati. Once all the warnings have been removed for a
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particular variable, we'll switch it to obsolete, and any references will become
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errors.
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### envsetup.sh variables with make equivalents
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| instead of | use |
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|--------------------------------------------------------------|----------------------|
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| OUT {#OUT} | OUT_DIR |
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| ANDROID_HOST_OUT {#ANDROID_HOST_OUT} | HOST_OUT |
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| ANDROID_PRODUCT_OUT {#ANDROID_PRODUCT_OUT} | PRODUCT_OUT |
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| ANDROID_HOST_OUT_TESTCASES {#ANDROID_HOST_OUT_TESTCASES} | HOST_OUT_TESTCASES |
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| ANDROID_TARGET_OUT_TESTCASES {#ANDROID_TARGET_OUT_TESTCASES} | TARGET_OUT_TESTCASES |
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All of the make variables may be relative paths from the current directory, or
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absolute paths if the output directory was specified as an absolute path. If you
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need an absolute variable, convert it to absolute during a rule, so that it's
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not expanded into the generated ninja file:
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``` make
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$(PRODUCT_OUT)/gen.img: my/src/path/gen.sh
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export PRODUCT_OUT=$$(cd $(PRODUCT_OUT); pwd); cd my/src/path; ./gen.sh -o $${PRODUCT_OUT}/gen.img
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```
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### ANDROID_BUILD_TOP {#ANDROID_BUILD_TOP}
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In Android.mk files, you can always assume that the current directory is the
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root of the source tree, so this can just be replaced with '.' (which is what
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$TOP is hardcoded to), or removed entirely. If you need an absolute path, see
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the instructions above.
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### Stop using PATH directly {#PATH}
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This isn't only set by envsetup.sh, but it is modified by it. Due to that it's
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rather easy for this to change between different shells, and it's not ideal to
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reread the makefiles every time this changes.
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In most cases, you shouldn't need to touch PATH at all. When you need to have a
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rule reference a particular binary that's part of the source tree or outputs,
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it's preferrable to just use the path to the file itself (since you should
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already be adding that as a dependency).
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Depending on the rule, passing the file path itself may not be feasible due to
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layers of unchangable scripts/binaries. In that case, be sure to add the
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dependency, but modify the PATH within the rule itself:
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``` make
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$(TARGET): myscript my/path/binary
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PATH=my/path:$$PATH myscript -o $@
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```
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### Stop using PYTHONPATH directly {#PYTHONPATH}
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Like PATH, this isn't only set by envsetup.sh, but it is modified by it. Due to
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that it's rather easy for this to change between different shells, and it's not
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ideal to reread the makefiles every time.
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The best solution here is to start switching to Soong's python building support,
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which packages the python interpreter, libraries, and script all into one file
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that no longer needs PYTHONPATH. See fontchain_lint for examples of this:
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* [external/fonttools/Lib/fontTools/Android.bp] for python_library_host
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* [frameworks/base/Android.bp] for python_binary_host
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* [frameworks/base/data/fonts/Android.mk] to execute the python binary
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If you still need to use PYTHONPATH, do so within the rule itself, just like
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path:
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``` make
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$(TARGET): myscript.py $(sort $(shell find my/python/lib -name '*.py'))
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PYTHONPATH=my/python/lib:$$PYTHONPATH myscript.py -o $@
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```
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### Other envsetup.sh variables {#other_envsetup_variables}
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* ANDROID_TOOLCHAIN
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* ANDROID_TOOLCHAIN_2ND_ARCH
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* ANDROID_DEV_SCRIPTS
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* ANDROID_EMULATOR_PREBUILTS
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* ANDROID_PRE_BUILD_PATHS
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These are all exported from envsetup.sh, but don't have clear equivalents within
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the makefile system. If you need one of them, you'll have to set up your own
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version.
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[build/soong/Changes.md]: https://android.googlesource.com/platform/build/soong/+/master/Changes.md
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[external/fonttools/Lib/fontTools/Android.bp]: https://android.googlesource.com/platform/external/fonttools/+/master/Lib/fontTools/Android.bp
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[frameworks/base/Android.bp]: https://android.googlesource.com/platform/frameworks/base/+/master/Android.bp
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[frameworks/base/data/fonts/Android.mk]: https://android.googlesource.com/platform/frameworks/base/+/master/data/fonts/Android.mk
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