Merge "Mark envsetup.sh vars as deprecated in makefiles" am: d7fcf6f4 am: efe230ce

# Build System Changes for Android.mk Writers

## Deprecating 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, we'll switch

this to obsolete, and any references will become errors.

### envsetup.sh variables with make equivalents

| instead of                                                   | use                  |

|--------------------------------------------------------------|----------------------|

| OUT {#OUT}                                                   | OUT_DIR              |

| 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 $@

```

### 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.

[build/soong/Changes.md]: https://android.googlesource.com/platform/build/soong/+/master/Changes.md

[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

# Android Make Build System

This is the Makefile-based portion of the Android Build System.

For documentation on how to run a build, see [Usage.txt](Usage.txt)

For a list of behavioral changes useful for Android.mk writers see

[Changes.md](Changes.md)

For an outdated reference on Android.mk files, see

[build-system.html](/core/build-system.html). Our Android.mk files look similar,

but are entirely different from the Android.mk files used by the NDK build

system. When searching for documentation elsewhere, ensure that it is for the

platform build system -- most are not.

This Makefile-based system is in the process of being replaced with [Soong], a

new build system written in Go. During the transition, all of these makefiles

are read by [Kati], and generate a ninja file instead of being executed

directly. That's combined with a ninja file read by Soong so that the build

graph of the two systems can be combined and run as one.

[Kati]: https://github.com/google/kati

[Soong]: https://android.googlesource.com/platform/build/soong/+/master

.DELETE_ON_ERROR:

# Mark variables deprecated/obsolete

$(KATI_deprecated_var PATH,Do not use PATH directly)

CHANGES_URL := https://android.googlesource.com/platform/build/+/master/Changes.md

$(KATI_deprecated_var PATH,Do not use PATH directly. See $(CHANGES_URL)#PATH)

$(KATI_deprecated_var PYTHONPATH,Do not use PYTHONPATH directly. See $(CHANGES_URL)#PYTHONPATH)

$(KATI_deprecated_var OUT,Use OUT_DIR instead. See $(CHANGES_URL)#OUT)

$(KATI_deprecated_var ANDROID_HOST_OUT,Use HOST_OUT instead. See $(CHANGES_URL)#ANDROID_HOST_OUT)

$(KATI_deprecated_var ANDROID_PRODUCT_OUT,Use PRODUCT_OUT instead. See $(CHANGES_URL)#ANDROID_PRODUCT_OUT)

$(KATI_deprecated_var ANDROID_HOST_OUT_TESTCASES,Use HOST_OUT_TESTCASES instead. See $(CHANGES_URL)#ANDROID_HOST_OUT_TESTCASES)

$(KATI_deprecated_var ANDROID_TARGET_OUT_TESTCASES,Use TARGET_OUT_TESTCASES instead. See $(CHANGES_URL)#ANDROID_TARGET_OUT_TESTCASES)

$(KATI_deprecated_var ANDROID_BUILD_TOP,Use '.' instead. See $(CHANGES_URL)#ANDROID_BUILD_TOP)

$(KATI_deprecated_var \

  ANDROID_TOOLCHAIN \

  ANDROID_TOOLCHAIN_2ND_ARCH \

  ANDROID_DEV_SCRIPTS \

  ANDROID_EMULATOR_PREBUILTS \

  ANDROID_PRE_BUILD_PATHS \

  ,See $(CHANGES_URL)#other_envsetup_variables)

CHANGES_URL :=

# Used to force goals to build.  Only use for conditionally defined goals.

.PHONY: FORCE

m -j [<goals>]              # Execute the configured build.

Usage of "m" imitates usage of the program "make".

See '"${SCRIPT_DIR}"'/README.txt for more info about build usage and concepts.

See '"${SCRIPT_DIR}"'/Usage.txt for more info about build usage and concepts.

Common goals are: