# Build System Changes for Android.mk Writers ## Perform validation of Soong plugins Each Soong plugin will require manual work to migrate to Bazel. In order to minimize the manual work outside of build/soong, we are restricting plugins to those that exist today and those in vendor or hardware directories. If you need to extend the build system via a plugin, please reach out to the build team via email android-building@googlegroups.com (external) for any questions, or see [go/soong](http://go/soong) (internal). To omit the validation, `BUILD_BROKEN_PLUGIN_VALIDATION` expects a list of plugins to omit from the validation. ## Python 2 to 3 migration The path set when running builds now makes the `python` executable point to python 3, whereas on previous versions it pointed to python 2. If you still have python 2 scripts, you can change the shebang line to use `python2` explicitly. This only applies for scripts run directly from makefiles, or from soong genrules. This behavior can be temporarily overridden by setting the `BUILD_BROKEN_PYTHON_IS_PYTHON2` environment variable to `true`. It's only an environment variable and not a product config variable because product config sometimes calls python code. In addition, `python_*` soong modules no longer allow python 2. This can be temporarily overridden by setting the `BUILD_BROKEN_USES_SOONG_PYTHON2_MODULES` product configuration variable to `true`. Python 2 is slated for complete removal in V. ## Stop referencing sysprop_library directly from cc modules For the migration to Bazel, we are no longer mapping sysprop_library targets to their generated `cc_library` counterparts when dependning on them from a cc module. Instead, directly depend on the generated module by prefixing the module name with `lib`. For example, depending on the following module: ``` sysprop_library { name: "foo", srcs: ["foo.sysprop"], } ``` from a module named `bar` can be done like so: ``` cc_library { name: "bar", srcs: ["bar.cc"], deps: ["libfoo"], } ``` Failure to do this will result in an error about a missing variant. ## Gensrcs starts disallowing depfile property To migrate all gensrcs to Bazel, we are restricting the use of depfile property because Bazel requires specifying the dependencies directly. To fix existing uses, remove depfile and directly specify all the dependencies in .bp files. For example: ``` gensrcs { name: "framework-cppstream-protos", tools: [ "aprotoc", "protoc-gen-cppstream", ], cmd: "mkdir -p $(genDir)/$(in) " + "&& $(location aprotoc) " + " --plugin=$(location protoc-gen-cppstream) " + " -I . " + " $(in) ", srcs: [ "bar.proto", ], output_extension: "srcjar", } ``` where `bar.proto` imports `external.proto` would become ``` gensrcs { name: "framework-cppstream-protos", tools: [ "aprotoc", "protoc-gen-cpptream", ], tool_files: [ "external.proto", ], cmd: "mkdir -p $(genDir)/$(in) " + "&& $(location aprotoc) " + " --plugin=$(location protoc-gen-cppstream) " + " $(in) ", srcs: [ "bar.proto", ], output_extension: "srcjar", } ``` as in https://android-review.googlesource.com/c/platform/frameworks/base/+/2125692/. `BUILD_BROKEN_DEPFILE` can be used to allowlist usage of depfile in `gensrcs`. If `depfile` is needed for generating javastream proto, `java_library` with `proto.type` set `stream` is the alternative solution. Sees https://android-review.googlesource.com/c/platform/packages/modules/Permission/+/2118004/ for an example. ## Genrule starts disallowing directory inputs To better specify the inputs to the build, we are restricting use of directories as inputs to genrules. To fix existing uses, change inputs to specify the inputs and update the command accordingly. For example: ``` genrule: { name: "foo", srcs: ["bar"], cmd: "cp $(location bar)/*.xml $(gendir)", ... } ``` would become ``` genrule: { name: "foo", srcs: ["bar/*.xml"], cmd: "cp $(in) $(gendir)", ... } ``` `BUILD_BROKEN_INPUT_DIR_MODULES` can be used to allowlist specific directories with genrules that have input directories. ## Dexpreopt starts enforcing `` checks (for Java modules) In order to construct correct class loader context for dexpreopt, build system needs to know about the shared library dependencies of Java modules listed in the `` tags in the manifest. Since the build system does not have access to the manifest contents, that information must be present in the build files. In simple cases Soong is able to infer it from its knowledge of Java SDK libraries and the `libs` property in Android.bp, but in more complex cases it is necessary to add the missing information in Android.bp/Android.mk manually. To specify a list of libraries for a given modules, use: * Android.bp properties: `uses_libs`, `optional_uses_libs` * Android.mk variables: `LOCAL_USES_LIBRARIES`, `LOCAL_OPTIONAL_USES_LIBRARIES` If a library is in `libs`, it usually should *not* be added to the above properties, and Soong should be able to infer the `` tag. But sometimes a library also needs additional information in its Android.bp/Android.mk file (e.g. when it is a `java_library` rather than a `java_sdk_library`, or when the library name is different from its module name, or when the module is defined in Android.mk rather than Android.bp). In such cases it is possible to tell the build system that the library provides a `` with a given name (however, this is discouraged and will be deprecated in the future, and it is recommended to fix the underlying problem): * Android.bp property: `provides_uses_lib` * Android.mk variable: `LOCAL_PROVIDES_USES_LIBRARY` It is possible to disable the check on a per-module basis. When doing that it is also recommended to disable dexpreopt, as disabling a failed check will result in incorrect class loader context recorded in the .odex file, which will cause class loader context mismatch and dexopt at first boot. * Android.bp property: `enforce_uses_lib` * Android.mk variable: `LOCAL_ENFORCE_USES_LIBRARIES` Finally, it is possible to globally disable the check: * For a given product: `PRODUCT_BROKEN_VERIFY_USES_LIBRARIES := true` * On the command line: `RELAX_USES_LIBRARY_CHECK=true` The environment variable overrides the product variable, so it is possible to disable the check for a product, but quickly re-enable it for a local build. ## `LOCAL_REQUIRED_MODULES` requires listed modules to exist {#BUILD_BROKEN_MISSING_REQUIRED_MODULES} Modules listed in `LOCAL_REQUIRED_MODULES`, `LOCAL_HOST_REQUIRED_MODULES` and `LOCAL_TARGET_REQUIRED_MODULES` need to exist unless `ALLOW_MISSING_DEPENDENCIES` is set. To temporarily relax missing required modules check, use: `BUILD_BROKEN_MISSING_REQUIRED_MODULES := true` ## Changes in system properties settings ### Product variables System properties for each of the partition is supposed to be set via following product config variables. For system partition, * `PRODUCT_SYSTEM_PROPERTIES` * `PRODUCT_SYSTEM_DEFAULT_PROPERTIES` is highly discouraged. Will be deprecated. For vendor partition, * `PRODUCT_VENDOR_PROPERTIES` * `PRODUCT_PROPERTY_OVERRIDES` is highly discouraged. Will be deprecated. * `PRODUCT_DEFAULT_PROPERTY_OVERRIDES` is also discouraged. Will be deprecated. For odm partition, * `PRODUCT_ODM_PROPERTIES` For system_ext partition, * `PRODUCT_SYSTEM_EXT_PROPERTIES` For product partition, * `PRODUCT_PRODUCT_PROPERTIES` ### Duplication is not allowed within a partition For each partition, having multiple sysprop assignments for the same name is prohibited. For example, the following will now trigger an error: `PRODUCT_VENDOR_PROPERTIES += foo=true foo=false` Having duplication across partitions are still allowed. So, the following is not an error: `PRODUCT_VENDOR_PROPERTIES += foo=true` `PRODUCT_SYSTEM_PROPERTIES += foo=false` In that case, the final value is determined at runtime. The precedence is * product * odm * vendor * system_ext * system So, `foo` becomes `true` because vendor has higher priority than system. To temporarily turn the build-time restriction off, use `BUILD_BROKEN_DUP_SYSPROP := true` ### Optional assignments System properties can now be set as optional using the new syntax: `name ?= value` Then the system property named `name` gets the value `value` only when there is no other non-optional assignments having the same name. For example, the following is allowed and `foo` gets `true` `PRODUCT_VENDOR_PROPERTIES += foo=true foo?=false` Note that the order between the optional and the non-optional assignments doesn't matter. The following gives the same result as above. `PRODUCT_VENDOR_PROPERTIES += foo?=false foo=true` Optional assignments can be duplicated and in that case their order matters. Specifically, the last one eclipses others. `PRODUCT_VENDOR_PROPERTIES += foo?=apple foo?=banana foo?=mango` With above, `foo` becomes `mango` since its the last one. Note that this behavior is different from the previous behavior of preferring the first one. To go back to the original behavior for compatability reason, use: `BUILD_BROKEN_DUP_SYSPROP := true` ## ELF prebuilts in `PRODUCT_COPY_FILES` {#BUILD_BROKEN_ELF_PREBUILT_PRODUCT_COPY_FILES} ELF prebuilts in `PRODUCT_COPY_FILES` that are installed into these paths are an error: * `/bin/*` * `/lib/*` * `/lib64/*` Define prebuilt modules and add them to `PRODUCT_PACKAGES` instead. To temporarily relax this check and restore the behavior prior to this change, set `BUILD_BROKEN_ELF_PREBUILT_PRODUCT_COPY_FILES := true` in `BoardConfig.mk`. ## COPY_HEADERS usage now produces warnings {#copy_headers} We've considered `BUILD_COPY_HEADERS`/`LOCAL_COPY_HEADERS` to be deprecated for a long time, and the places where it's been able to be used have shrinked over the last several releases. Equivalent functionality is not available in Soong. See the [build/soong/docs/best_practices.md#headers] for more information about how best to handle headers in Android. ## `m4` is not available on `$PATH` There is a prebuilt of it available in prebuilts/build-tools, and a make variable `M4` that contains the path. Beyond the direct usage, whenever you use bison or flex directly, they call m4 behind the scene, so you must set the M4 environment variable (and depend upon it for incremental build correctness): ``` $(intermediates)/foo.c: .KATI_IMPLICIT_OUTPUTS := $(intermediates)/foo.h $(intermediates)/foo.c: $(LOCAL_PATH)/foo.y $(M4) $(BISON) $(BISON_DATA) M4=$(M4) $(BISON) ... ``` ## Rules executed within limited environment With `ALLOW_NINJA_ENV=false` (soon to be the default), ninja, and all the rules/actions executed within it will only have access to a limited number of environment variables. Ninja does not track when environment variables change in order to trigger rebuilds, so changing behavior based on arbitrary variables is not safe with incremental builds. Kati and Soong can safely use environment variables, so the expectation is that you'd embed any environment variables that you need to use within the command line generated by those tools. See the [export section](#export_keyword) below for examples. For a temporary workaround, you can set `ALLOW_NINJA_ENV=true` in your environment to restore the previous behavior, or set `BUILD_BROKEN_NINJA_USES_ENV_VAR := ...` in your `BoardConfig.mk` to allow specific variables to be passed through until you've fixed the rules. ## LOCAL_C_INCLUDES outside the source/output trees are an error {#BUILD_BROKEN_OUTSIDE_INCLUDE_DIRS} Include directories are expected to be within the source tree (or in the output directory, generated during the build). This has been checked in some form since Oreo, but now has better checks. There's now a `BUILD_BROKEN_OUTSIDE_INCLUDE_DIRS` variable, that when set, will turn these errors into warnings temporarily. I don't expect this to last more than a release, since they're fairly easy to clean up. Neither of these cases are supported by Soong, and will produce errors when converting your module. ### Absolute paths This has been checked since Oreo. The common reason to hit this is because a makefile is calculating a path, and ran abspath/realpath/etc. This is a problem because it makes your build non-reproducible. It's very unlikely that your source path is the same on every machine. ### Using `../` to leave the source/output directories This is the new check that has been added. In every case I've found, this has been a mistake in the Android.mk -- assuming that `LOCAL_C_INCLUDES` (which is relative to the top of the source tree) acts like `LOCAL_SRC_FILES` (which is relative to `LOCAL_PATH`). Since this usually isn't a valid path, you can almost always just remove the offending line. ## `BOARD_HAL_STATIC_LIBRARIES` and `LOCAL_HAL_STATIC_LIBRARIES` are obsolete {#BOARD_HAL_STATIC_LIBRARIES} Define proper HIDL / Stable AIDL HAL instead. * For libhealthd, use health HAL. See instructions for implementing health HAL: * [hardware/interfaces/health/2.1/README.md] for health 2.1 HAL (recommended) * [hardware/interfaces/health/1.0/README.md] for health 1.0 HAL * For libdumpstate, use at least Dumpstate HAL 1.0. ## PRODUCT_STATIC_BOOT_CONTROL_HAL is obsolete {#PRODUCT_STATIC_BOOT_CONTROL_HAL} `PRODUCT_STATIC_BOOT_CONTROL_HAL` was the workaround to allow sideloading with statically linked boot control HAL, before shared library HALs were supported under recovery. Android Q has added such support (HALs will be loaded in passthrough mode), and the workarounds are being removed. Targets should build and install the recovery variant of boot control HAL modules into recovery image, similar to the ones installed for normal boot. See the change to crosshatch for example of this: * [device/google/crosshatch/bootctrl/Android.bp] for `bootctrl.sdm845` building rules * [device/google/crosshatch/device.mk] for installing `bootctrl.sdm845.recovery` and `android.hardware.boot@1.0-impl.recovery` into recovery image [device/google/crosshatch/bootctrl/Android.bp]: https://android.googlesource.com/device/google/crosshatch/+/master/bootctrl/Android.bp [device/google/crosshatch/device.mk]: https://android.googlesource.com/device/google/crosshatch/+/master/device.mk ## Deprecation of `BUILD_*` module types See [build/make/Deprecation.md](Deprecation.md) for the current status. ## `PRODUCT_HOST_PACKAGES` split from `PRODUCT_PACKAGES` {#PRODUCT_HOST_PACKAGES} Previously, adding a module to `PRODUCT_PACKAGES` that supported both the host and the target (`host_supported` in Android.bp; two modules with the same name in Android.mk) would cause both to be built and installed. In many cases you only want either the host or target versions to be built/installed by default, and would be over-building with both. So `PRODUCT_PACKAGES` will be changing to just affect target modules, while `PRODUCT_HOST_PACKAGES` is being added for host modules. Functional differences between `PRODUCT_PACKAGES` and `PRODUCT_HOST_PACKAGES`: * `PRODUCT_HOST_PACKAGES` does not have `_ENG`/`_DEBUG` variants, as that's a property of the target, not the host. * `PRODUCT_HOST_PACKAGES` does not support `LOCAL_MODULE_OVERRIDES`. * `PRODUCT_HOST_PACKAGES` requires listed modules to exist, and be host modules. (Unless `ALLOW_MISSING_DEPENDENCIES` is set) This is still an active migration, so currently it still uses `PRODUCT_PACKAGES` to make installation decisions, but verifies that if we used `PRODUCT_HOST_PACKAGES`, it would trigger installation for all of the same host packages. This check ignores shared libraries, as those are not normally necessary in `PRODUCT_*PACKAGES`, and tended to be over-built (especially the 32-bit variants). Future changes will switch installation decisions to `PRODUCT_HOST_PACKAGES` for host modules, error when there's a host-only module in `PRODUCT_PACKAGES`, and do some further cleanup where `LOCAL_REQUIRED_MODULES` are still merged between host and target modules with the same name. ## `*.c.arm` / `*.cpp.arm` deprecation {#file_arm} In Android.mk files, you used to be able to change LOCAL_ARM_MODE for each source file by appending `.arm` to the end of the filename in `LOCAL_SRC_FILES`. Soong does not support this uncommonly used behavior, instead expecting those files to be split out into a separate static library that chooses `arm` over `thumb` for the entire library. This must now also be done in Android.mk files. ## Windows cross-compiles no longer supported in Android.mk Modules that build for Windows (our only `HOST_CROSS` OS currently) must now be defined in `Android.bp` files. ## `LOCAL_MODULE_TAGS := eng debug` are obsolete {#LOCAL_MODULE_TAGS} `LOCAL_MODULE_TAGS` value `eng` and `debug` are now obsolete. They allowed modules to specify that they should always be installed on `-eng`, or `-eng` and `-userdebug` builds. This conflicted with the ability for products to specify which modules should be installed, effectively making it impossible to build a stripped down product configuration that did not include those modules. For the equivalent functionality, specify the modules in `PRODUCT_PACKAGES_ENG` or `PRODUCT_PACKAGES_DEBUG` in the appropriate product makefiles. Core android packages like `su` got added to the list in `build/make/target/product/base_system.mk`, but for device-specific modules there are often better base product makefiles to use instead. ## `USER` deprecation {#USER} `USER` will soon be `nobody` in many cases due to the addition of a sandbox around the Android build. Most of the time you shouldn't need to know the identity of the user running the build, but if you do, it's available in the make variable `BUILD_USERNAME` for now. Similarly, the `hostname` tool will also be returning a more consistent value of `android-build`. The real value is available as `BUILD_HOSTNAME`. ## `BUILD_NUMBER` removal from Android.mk {#BUILD_NUMBER} `BUILD_NUMBER` should not be used directly in Android.mk files, as it would trigger them to be re-read every time the `BUILD_NUMBER` changes (which it does on every build server build). If possible, just remove the use so that your builds are more reproducible. If you do need it, use `BUILD_NUMBER_FROM_FILE`: ``` make $(LOCAL_BUILT_MODULE): mytool --build_number $(BUILD_NUMBER_FROM_FILE) -o $@ ``` That will expand out to a subshell that will read the current `BUILD_NUMBER` whenever it's run. It will not re-run your command if the build number has changed, so incremental builds will have the build number from the last time the particular output was rebuilt. ## `DIST_DIR`, `dist_goal`, and `dist-for-goals` {#dist} `DIST_DIR` and `dist_goal` are no longer available when reading Android.mk files (or other build tasks). Always use `dist-for-goals` instead, which takes a PHONY goal, and a list of files to copy to `$DIST_DIR`. Whenever `dist` is specified, and the goal would be built (either explicitly on the command line, or as a dependency of something on the command line), that file will be copied into `$DIST_DIR`. For example, ``` make $(call dist-for-goals,foo,bar/baz) ``` will copy `bar/baz` into `$DIST_DIR/baz` when `m foo dist` is run. #### FILE_NAME_TAG {#FILE_NAME_TAG} To embed the `BUILD_NUMBER` (or for local builds, `eng.${USER}`), include `FILE_NAME_TAG_PLACEHOLDER` in the destination: ``` make # you can use dist-for-goals-with-filenametag function $(call dist-for-goals-with-filenametag,foo,bar.zip) # or use FILE_NAME_TAG_PLACEHOLDER manually $(call dist-for-goals,foo,bar.zip:baz-FILE_NAME_TAG_PLACEHOLDER.zip) ``` Which will produce `$DIST_DIR/baz-1234567.zip` on build servers which set `BUILD_NUMBER=1234567`, or `$DIST_DIR/baz-eng.builder.zip` for local builds. If you just want to append `BUILD_NUMBER` at the end of basename, use `dist-for-goals-with-filenametag` instead of `dist-for-goals`. #### Renames during copy Instead of specifying just a file, a destination name can be specified, including subdirectories: ``` make $(call dist-for-goals,foo,bar/baz:logs/foo.log) ``` will copy `bar/baz` into `$DIST_DIR/logs/foo.log` when `m foo dist` is run. ## `.PHONY` rule enforcement {#phony_targets} There are several new warnings/errors meant to ensure the proper use of `.PHONY` targets in order to improve the speed and reliability of incremental builds. `.PHONY`-marked targets are often used as shortcuts to provide "friendly" names for real files to be built, but any target marked with `.PHONY` is also always considered dirty, needing to be rebuilt every build. This isn't a problem for aliases or one-off user-requested operations, but if real builds steps depend on a `.PHONY` target, it can get quite expensive for what should be a tiny build. ``` make ...mk:42: warning: PHONY target "out/.../foo" looks like a real file (contains a "/") ``` Between this warning and the next, we're requiring that `.PHONY` targets do not have "/" in them, and real file targets do have a "/". This makes it more obvious when reading makefiles what is happening, and will help the build system differentiate these in the future too. ``` make ...mk:42: warning: writing to readonly directory: "kernel-modules" ``` This warning will show up for one of two reasons: 1. The target isn't intended to be a real file, and should be marked with `.PHONY`. This would be the case for this example. 2. The target is a real file, but it's outside the output directories. All outputs from the build system should be within the output directory, otherwise `m clean` is unable to clean the build, and future builds may not work properly. ``` make ...mk:42: warning: real file "out/.../foo" depends on PHONY target "buildbins" ``` If the first target isn't intended to be a real file, then it should be marked with `.PHONY`, which will satisfy this warning. This isn't the case for this example, as we require `.PHONY` targets not to have '/' in them. If the second (PHONY) target is a real file, it may unnecessarily be marked with `.PHONY`. ### `.PHONY` and calling other build systems One common pattern (mostly outside AOSP) that we've seen hit these warning is when building with external build systems (firmware, bootloader, kernel, etc). Those are often marked as `.PHONY` because the Android build system doesn't have enough dependencies to know when to run the other build system again during an incremental build. We recommend to build these outside of Android, and deliver prebuilts into the Android tree instead of decreasing the speed and reliability of the incremental Android build. In cases where that's not desired, to preserve the speed of Android incrementals, over-specifying dependencies is likely a better option than marking it with `.PHONY`: ``` make out/target/.../zImage: $(sort $(shell find -L $(KERNEL_SRCDIR))) ... ``` For reliability, many of these other build systems do not guarantee the same level of incremental build assurances as the Android Build is attempting to do -- without custom checks, Make doesn't rebuild objects when CFLAGS change, etc. In order to fix this, our recommendation is to do clean builds for each of these external build systems every time anything they rely on changes. For relatively smaller builds (like the kernel), this may be reasonable as long as you're not trying to actively debug the kernel. ## `export` and `unexport` deprecation {#export_keyword} The `export` and `unexport` keywords are obsolete, and will throw errors when used. Device specific configuration should not be able to affect common core build steps -- we're looking at triggering build steps to be invalidated if the set of environment variables they can access changes. If device specific configuration is allowed to change those, switching devices with the same output directory could become significantly more expensive than it already can be. If used during Android.mk files, and later tasks, it is increasingly likely that they are being used incorrectly. Attempting to change the environment for a single build step, and instead setting it for hundreds of thousands. It is not recommended to just move the environment variable setting outside of the build (in vendorsetup.sh, or some other configuration script or wrapper). We expect to limit the environment variables that the build respects in the future, others will be cleared. (There will be methods to get custom variables into the build, just not to every build step) Instead, write the export commands into the rule command lines themselves: ``` make $(intermediates)/generated_output.img: rm -rf $@ export MY_ENV_A="$(MY_A)"; make ... ``` If you want to set many environment variables, and/or use them many times, write them out to a script and source the script: ``` make envsh := $(intermediates)/env.sh $(envsh): rm -rf $@ echo 'export MY_ENV_A="$(MY_A)"' >$@ echo 'export MY_ENV_B="$(MY_B)"' >>$@ $(intermediates)/generated_output.img: PRIVATE_ENV := $(envsh) $(intermediates)/generated_output.img: $(envsh) a/b/c/package.sh rm -rf $@ source $(PRIVATE_ENV); make ... source $(PRIVATE_ENV); a/b/c/package.sh ... ``` ## Implicit make rules are obsolete {#implicit_rules} Implicit rules look something like the following: ``` make $(TARGET_OUT_SHARED_LIBRARIES)/%_vendor.so: $(TARGET_OUT_SHARED_LIBRARIES)/%.so ... %.o : %.foo ... ``` These can have wide ranging effects across unrelated modules, so they're now obsolete. Instead, use static pattern rules, which are similar, but explicitly match the specified outputs: ``` make libs := $(foreach lib,libfoo libbar,$(TARGET_OUT_SHARED_LIBRARIES)/$(lib)_vendor.so) $(libs): %_vendor.so: %.so ... files := $(wildcard $(LOCAL_PATH)/*.foo) gen := $(patsubst $(LOCAL_PATH)/%.foo,$(intermediates)/%.o,$(files)) $(gen): %.o : %.foo ... ``` ## Removing '/' from Valid Module Names {#name_slash} The build system uses module names in path names in many places. Having an extra '/' or '../' being inserted can cause problems -- and not just build breaks, but stranger invalid behavior. In every case we've seen, the fix is relatively simple: move the directory into `LOCAL_MODULE_RELATIVE_PATH` (or `LOCAL_MODULE_PATH` if you're still using it). If this causes multiple modules to be named the same, use unique module names and `LOCAL_MODULE_STEM` to change the installed file name: ``` make include $(CLEAR_VARS) LOCAL_MODULE := ver1/code.bin LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/firmware ... include $(BUILD_PREBUILT) include $(CLEAR_VARS) LOCAL_MODULE := ver2/code.bin LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/firmware ... include $(BUILD_PREBUILT) ``` Can be rewritten as: ``` include $(CLEAR_VARS) LOCAL_MODULE := ver1_code.bin LOCAL_MODULE_STEM := code.bin LOCAL_MODULE_PATH := $(TARGET_OUT_VENDOR)/firmware/ver1 ... include $(BUILD_PREBUILT) include $(CLEAR_VARS) LOCAL_MODULE := ver2_code.bin LOCAL_MODULE_STEM := code.bin LOCAL_MODULE_PATH := $(TARGET_OUT_VENDOR)/firmware/ver2 ... include $(BUILD_PREBUILT) ``` You just need to make sure that any other references (`PRODUCT_PACKAGES`, `LOCAL_REQUIRED_MODULES`, etc) are converted to the new names. ## Valid Module Names {#name} We've adopted lexical requirements very similar to [Bazel's requirements](https://docs.bazel.build/versions/master/build-ref.html#name) for target names. Valid characters are `a-z`, `A-Z`, `0-9`, and the special characters `_.+-=,@~`. This currently applies to `LOCAL_PACKAGE_NAME`, `LOCAL_MODULE`, and `LOCAL_MODULE_SUFFIX`, and `LOCAL_MODULE_STEM*`. Many other characters already caused problems if you used them, so we don't expect this to have a large effect. ## PATH Tools {#PATH_Tools} The build has started restricting the external host tools usable inside the build. This will help ensure that build results are reproducible across different machines, and catch mistakes before they become larger issues. To start with, this includes replacing the $PATH with our own directory of tools, mirroring that of the host PATH. The only difference so far is the removal of the host GCC tools. Anything that is not explicitly in the configuration as allowed will continue functioning, but will generate a log message. This is expected to become more restrictive over time. The configuration is located in build/soong/ui/build/paths/config.go, and contains all the common tools in use in many builds. Anything not in that list will currently print a warning in the `$OUT_DIR/soong.log` file, including the command and arguments used, and the process tree in order to help locate the usage. In order to fix any issues brought up by these checks, the best way to fix them is to use tools checked into the tree -- either as prebuilts, or building them as host tools during the build. As a temporary measure, you can set `TEMPORARY_DISABLE_PATH_RESTRICTIONS=true` in your environment to temporarily turn off the error checks and allow any tool to be used (with logging). Beware that GCC didn't work well with the interposer used for logging, so this may not help in all cases. ## Deprecating / obsoleting envsetup.sh variables in Makefiles It is not required to source envsetup.sh before running a build. Many scripts, including a majority of our automated build systems, do not do so. Make will transparently make every environment variable available as a make variable. This means that relying on environment variables only set up in envsetup.sh will produce different output for local users and scripted users. Many of these variables also include absolute path names, which we'd like to keep out of the generated files, so that you don't need to do a full rebuild if you move the source tree. To fix this, we're marking the variables that are set in envsetup.sh as deprecated in the makefiles. This will trigger a warning every time one is read (or written) inside Kati. Once all the warnings have been removed for a particular variable, we'll switch it to obsolete, and any references will become errors. ### envsetup.sh variables with make equivalents | instead of | use | |--------------------------------------------------------------|----------------------| | OUT {#OUT} | PRODUCT_OUT | | ANDROID_HOST_OUT {#ANDROID_HOST_OUT} | HOST_OUT | | ANDROID_PRODUCT_OUT {#ANDROID_PRODUCT_OUT} | PRODUCT_OUT | | ANDROID_HOST_OUT_TESTCASES {#ANDROID_HOST_OUT_TESTCASES} | HOST_OUT_TESTCASES | | ANDROID_TARGET_OUT_TESTCASES {#ANDROID_TARGET_OUT_TESTCASES} | TARGET_OUT_TESTCASES | All of the make variables may be relative paths from the current directory, or absolute paths if the output directory was specified as an absolute path. If you need an absolute variable, convert it to absolute during a rule, so that it's not expanded into the generated ninja file: ``` make $(PRODUCT_OUT)/gen.img: my/src/path/gen.sh export PRODUCT_OUT=$$(cd $(PRODUCT_OUT); pwd); cd my/src/path; ./gen.sh -o $${PRODUCT_OUT}/gen.img ``` ### ANDROID_BUILD_TOP {#ANDROID_BUILD_TOP} In Android.mk files, you can always assume that the current directory is the root of the source tree, so this can just be replaced with '.' (which is what $TOP is hardcoded to), or removed entirely. If you need an absolute path, see the instructions above. ### Stop using PATH directly {#PATH} This isn't only set by envsetup.sh, but it is modified by it. Due to that it's rather easy for this to change between different shells, and it's not ideal to reread the makefiles every time this changes. In most cases, you shouldn't need to touch PATH at all. When you need to have a rule reference a particular binary that's part of the source tree or outputs, it's preferrable to just use the path to the file itself (since you should already be adding that as a dependency). Depending on the rule, passing the file path itself may not be feasible due to layers of unchangable scripts/binaries. In that case, be sure to add the dependency, but modify the PATH within the rule itself: ``` make $(TARGET): myscript my/path/binary PATH=my/path:$$PATH myscript -o $@ ``` ### Stop using PYTHONPATH directly {#PYTHONPATH} Like PATH, this isn't only set by envsetup.sh, but it is modified by it. Due to that it's rather easy for this to change between different shells, and it's not ideal to reread the makefiles every time. The best solution here is to start switching to Soong's python building support, which packages the python interpreter, libraries, and script all into one file that no longer needs PYTHONPATH. See fontchain_lint for examples of this: * [external/fonttools/Lib/fontTools/Android.bp] for python_library_host * [frameworks/base/Android.bp] for python_binary_host * [frameworks/base/data/fonts/Android.mk] to execute the python binary If you still need to use PYTHONPATH, do so within the rule itself, just like path: ``` make $(TARGET): myscript.py $(sort $(shell find my/python/lib -name '*.py')) PYTHONPATH=my/python/lib:$$PYTHONPATH myscript.py -o $@ ``` ### Stop using PRODUCT_COMPATIBILITY_MATRIX_LEVEL_OVERRIDE directly {#PRODUCT_COMPATIBILITY_MATRIX_LEVEL_OVERRIDE} Specify Framework Compatibility Matrix Version in device manifest by adding a `target-level` attribute to the root element ``. If `PRODUCT_COMPATIBILITY_MATRIX_LEVEL_OVERRIDE` is 26 or 27, you can add `"target-level"="1"` to your device manifest instead. ### Stop using USE_CLANG_PLATFORM_BUILD {#USE_CLANG_PLATFORM_BUILD} Clang is the default and only supported Android compiler, so there is no reason for this option to exist. ### Stop using clang property The clang property has been deleted from Soong. To fix any build errors, remove the clang property from affected Android.bp files using bpmodify. ``` make go run bpmodify.go -w -m=module_name -remove-property=true -property=clang filepath ``` `BUILD_BROKEN_CLANG_PROPERTY` can be used as temporarily workaround ### Stop using clang_cflags and clang_asflags clang_cflags and clang_asflags are deprecated. To fix any build errors, use bpmodify to either - move the contents of clang_asflags/clang_cflags into asflags/cflags or - delete clang_cflags/as_flags as necessary To Move the contents: ``` make go run bpmodify.go -w -m=module_name -move-property=true -property=clang_cflags -new-location=cflags filepath ``` To Delete: ``` make go run bpmodify.go -w -m=module_name -remove-property=true -property=clang_cflags filepath ``` `BUILD_BROKEN_CLANG_ASFLAGS` and `BUILD_BROKEN_CLANG_CFLAGS` can be used as temporarily workarounds ### Other envsetup.sh variables {#other_envsetup_variables} * ANDROID_TOOLCHAIN * ANDROID_TOOLCHAIN_2ND_ARCH * ANDROID_DEV_SCRIPTS * ANDROID_EMULATOR_PREBUILTS * ANDROID_PRE_BUILD_PATHS These are all exported from envsetup.sh, but don't have clear equivalents within the makefile system. If you need one of them, you'll have to set up your own version. ## Soong config variables ### Soong config string variables must list all values they can be set to In order to facilitate the transition to bazel, all soong_config_string_variables must only be set to a value listed in their `values` property, or an empty string. It is a build error otherwise. Example Android.bp: ``` soong_config_string_variable { name: "my_string_variable", values: [ "foo", "bar", ], } soong_config_module_type { name: "my_cc_defaults", module_type: "cc_defaults", config_namespace: "my_namespace", variables: ["my_string_variable"], properties: [ "shared_libs", "static_libs", ], } ``` Product config: ``` $(call soong_config_set,my_namespace,my_string_variable,baz) # Will be an error as baz is not listed in my_string_variable's values. ``` [build/soong/Changes.md]: https://android.googlesource.com/platform/build/soong/+/master/Changes.md [build/soong/docs/best_practices.md#headers]: https://android.googlesource.com/platform/build/soong/+/master/docs/best_practices.md#headers [external/fonttools/Lib/fontTools/Android.bp]: https://android.googlesource.com/platform/external/fonttools/+/master/Lib/fontTools/Android.bp [frameworks/base/Android.bp]: https://android.googlesource.com/platform/frameworks/base/+/master/Android.bp [frameworks/base/data/fonts/Android.mk]: https://android.googlesource.com/platform/frameworks/base/+/master/data/fonts/Android.mk [hardware/interfaces/health/1.0/README.md]: https://android.googlesource.com/platform/hardware/interfaces/+/master/health/1.0/README.md [hardware/interfaces/health/2.1/README.md]: https://android.googlesource.com/platform/hardware/interfaces/+/master/health/2.1/README.md