When developing a component, for example a C++ shared library, it must be
possible to easily rebuild just that component, and not have to wait more than a
couple seconds for dependency checks, and not have to wait for unneeded
components to be built.
Both Environment and Config File Based Settings
To set the target, and other options, some people on the team like to have a
configuration file in a directory so they do not have an environment setup
script to run, and others want an environment setup script to run so they can
run builds in different terminals on the same tree, or switch back and forth
in one terminal. We will support both.
Object File Directory / make clean
Object files and other intermediate files will be generated into a directory
that is separate from the source tree. The goal is to have make clean be
"rm -rf " in the tree root directory. The primary goals of
this are to simplify searching the source tree, and to make "make clean" more
reliable.
SDK
The SDK will be a tarball that will allow non-OS-developers to write apps.
The apps will actually be built by first building the SDK, and then building
the apps against that SDK. This will hopefully (1) make writing apps easier
for us, because we won't have to rebuild the OS as much, and we can use the
standard java-app development tools, and (2) allow us to dog-food the SDK, to
help ensure its quality. Cedric has suggested (and I agree) that apps built
from the SDK should be built with ant. Stay tuned for more details as we
figure out exactly how this will work.
Dependecies
Dependencies should all be automatic. Unless there is a custom tool involved
(e.g. the webkit has several), the dependencies for shared and static libraries,
.c, .cpp, .h, .java, java libraries, etc., should all work without intervention
in the Android.mk file.
Hiding command lines
The default of the build system will be to hide the command lines being
executed for make steps. It will be possible to override this by specifying
the showcommands pseudo-target, and possibly by setting an environment
variable.
Wildcard source files
Wildcarding source file will be discouraged. It may be useful in some
scenarios. The default $(wildcard *) will not work due to the
current directory being set to the root of the build tree.
Multiple targets in one directory
It will be possible to generate more than one target from a given
subdirectory. For example, libutils generates a shared library for the target
and a static library for the host.
Makefile fragments for modules
Android.mk is the standard name for the makefile fragments that
control the building of a given module. Only the top directory should
have a file named "Makefile".
Use shared libraries
Currently, the simulator is not built to use shared libraries. This should
be fixed, and now is a good time to do it. This implies getting shared
libraries to work on Mac OS.
Nice to Have
These things would be nice to have, and this is a good place to record them,
however these are not promises.
Simultaneous Builds
The hope is to be able to do two builds for different combos in the same
tree at the same time, but this is a stretch goal, not a requirement.
Doing two builds in the same tree, not at the same time must work. (update:
it's looking like we'll get the two builds at the same time working)
Deleting headers (or other dependecies)
Problems can arise if you delete a header file that is referenced in
".d" files. The easy way to deal with this is "make clean". There
should be a better way to handle it. (from fadden)
One way of solving this is introducing a dependency on the directory. The
problem is that this can create extra dependecies and slow down the build.
It's a tradeoff.
Multiple builds
General way to perform builds across the set of known platforms. This
would make it easy to perform multiple platform builds when testing a
change, and allow a wide-scale "make clean". Right now the buildspec.mk
or environment variables need to be updated before each build. (from fadden)
Aftermarket Locales and Carrier
We will eventually need to add support for creating locales and carrier
customizations to the SDK, but that will not be addressed right now.
If you source the file build/envsetup.sh into your bash environment,
. build/envsetup.shyou'll get a few helpful shell functions:
printconfig - Prints the current configuration as set by the
lunch and choosecombo commands.
m - Runs make from the top of the tree. This is
useful because you can run make from within subdirectories. If you have the
TOP environment variable set, it uses that. If you don't, it looks
up the tree from the current directory, trying to find the top of the tree.
croot - cd to the top of the tree.
sgrep - grep for the regex you provide in all .c, .cpp, .h, .java,
and .xml files below the current directory.
Build flavors/types
When building for a particular product, it's often useful to have minor
variations on what is ultimately the final release build. These are the
currently-defined "flavors" or "types" (we need to settle on a real name
for these).
eng
This is the default flavor. A plain "make" is the
same as "make eng". droid is an alias
for eng.
Installs non-APK modules that have no tags specified.
Installs APKs according to the product definition files, in
addition to tagged APKs.
ro.secure=0
ro.debuggable=1
ro.kernel.android.checkjni=1
adb is enabled by default.
user
"make user"
This is the flavor intended to be the final release bits.
Installs modules tagged with shell_$(TARGET_SHELL) and user.
Installs non-APK modules that have no tags specified.
Installs APKs according to the product definition files; tags
are ignored for APK modules.
ro.secure=1
ro.debuggable=0
adb is disabled by default.
userdebug
"make userdebug"
The same as user, except:
Also installs modules tagged with debug.
ro.debuggable=1
adb is enabled by default.
If you build one flavor and then want to build another, you should run
"make installclean" between the two makes to guarantee that
you don't pick up files installed by the previous flavor. "make
clean" will also suffice, but it takes a lot longer.
More pseudotargets
Sometimes you want to just build one thing. The following pseudotargets are
there for your convenience:
droid - make droid is the normal build. This target
is here because the default target has to have a name.
all - make all builds everything make
droid does, plus everything whose LOCAL_MODULE_TAGS do not
include the "droid" tag. The build server runs this to make sure
that everything that is in the tree and has an Android.mk builds.
clean-$(LOCAL_MODULE) and clean-$(LOCAL_PACKAGE_NAME) -
Let you selectively clean one target. For example, you can type
make clean-libutils and it will delete libutils.so and all of the
intermediate files, or you can type make clean-Home and it will
clean just the Home app.
clean - make clean deletes all of the output and
intermediate files for this configuration. This is the same as rm -rf
out/<configuration>/
clobber - make clobber deletes all of the output
and intermediate files for all configurations. This is the same as
rm -rf out/.
dataclean - make dataclean deletes contents of the data
directory inside the current combo directory. This is especially useful on the
simulator and emulator, where the persistent data remains present between
builds.
showcommands - showcommands is a modifier target
which causes the build system to show the actual command lines for the build
steps, instead of the brief descriptions. Most people don't like seeing the
actual commands, because they're quite long and hard to read, but if you need
to for debugging purposes, you can add showcommands to the list
of targets you build. For example make showcommands will build
the default android configuration, and make runtime showcommands
will build just the runtime, and targets that it depends on, while displaying
the full command lines. Please note that there are a couple places where the
commands aren't shown here. These are considered bugs, and should be fixed,
but they're often hard to track down. Please let
android-build-team know if you find
any.
LOCAL_MODULE - Anything you specify as a LOCAL_MODULE
in an Android.mk is made into a pseudotarget. For example, make
runtime might be shorthand for make
out/linux-x86-debug/system/bin/runtime (which would work), and
make libkjs might be shorthand for make
out/linux-x86-debug/system/lib/libkjs.so (which would also work).
targets - make targets will print a list of all of
the LOCAL_MODULE names you can make.
Use the templates/shared_library file, or the
templates/shared_library_host file.
Remember that on the target, we use shared libraries, and on the host,
we use static libraries, since executable size isn't as big an issue, and it
simplifies distribution in the SDK.
Static Libraries
Use the templates/static_library file, or the
templates/static_library_host file.
Remember that on the target, we use shared libraries, and on the host,
we use static libraries, since executable size isn't as big an issue, and it
simplifies distribution in the SDK.
ifeq ($(TARGET_BUILD_TYPE),release)
LOCAL_CFLAGS += -DNDEBUG=1
endif
# from libutils
ifeq ($(TARGET_OS),linux)
# Use the futex based mutex and condition variable
# implementation from android-arm because it's shared mem safe
LOCAL_SRC_FILES += futex_synchro.c
LOCAL_LDLIBS += -lrt -ldl
endif
INTERNAL_ - These variables are critical to functioning of
the build system, so you shouldn't create variables named like this, and
you probably shouldn't be messing with these variables in your makefiles.
HOST_ and TARGET_ - These contain the directories
and definitions that are specific to either the host or the target builds.
Do not set variables that start with HOST_ or TARGET_ in your makefiles.
BUILD_ and CLEAR_VARS - These contain the names of
well-defined template makefiles to include. Some examples are CLEAR_VARS
and BUILD_HOST_PACKAGE.
Any other name is fair-game for you to use in your Android.mk. However,
remember that this is a non-recursive build system, so it is possible that
your variable will be changed by another Android.mk included later, and be
different when the commands for your rule / module are executed.
LOCAL_ASSET_FILES
In Android.mk files that include $(BUILD_PACKAGE) set this
to the set of files you want built into your app. Usually:
LOCAL_ASSET_FILES += $(call find-subdir-assets)
This will probably change when we switch to ant for the apps' build
system.
LOCAL_CC
If you want to use a different C compiler for this module, set LOCAL_CC
to the path to the compiler. If LOCAL_CC is blank, the appropriate default
compiler is used.
LOCAL_CXX
If you want to use a different C++ compiler for this module, set LOCAL_CXX
to the path to the compiler. If LOCAL_CXX is blank, the appropriate default
compiler is used.
LOCAL_CFLAGS
If you have additional flags to pass into the C or C++ compiler, add
them here. For example:
LOCAL_CFLAGS += -DLIBUTILS_NATIVE=1
LOCAL_CPPFLAGS
If you have additional flags to pass into only the C++ compiler, add
them here. For example:
LOCAL_CPPFLAGS += -ffriend-injection
LOCAL_CPPFLAGS is guaranteed to be after LOCAL_CFLAGS
on the compile line, so you can use it to override flags listed in
LOCAL_CFLAGS.
LOCAL_CPP_EXTENSION
If your C++ files end in something other than ".cpp",
you can specify the custom extension here. For example:
LOCAL_CPP_EXTENSION := .cc
Note that all C++ files for a given module must have the same
extension; it is not currently possible to mix different extensions.
LOCAL_NO_DEFAULT_COMPILER_FLAGS
Normally, the compile line for C and C++ files includes global include
paths and global cflags. If LOCAL_NO_DEFAULT_COMPILER_FLAGS
is non-empty, none of the default includes or flags will be used when compiling
C and C++ files in this module.
LOCAL_C_INCLUDES, LOCAL_CFLAGS, and
LOCAL_CPPFLAGS will still be used in this case, as will
any DEBUG_CFLAGS that are defined for the module.
LOCAL_COPY_HEADERS
This will be going away.
The set of files to copy to the install include tree. You must also
supply LOCAL_COPY_HEADERS_TO.
This is going away because copying headers messes up the error messages, and
may lead to people editing those headers instead of the correct ones. It also
makes it easier to do bad layering in the system, which we want to avoid. We
also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
headers.
LOCAL_COPY_HEADERS_TO
This will be going away.
The directory within "include" to copy the headers listed in
LOCAL_COPY_HEADERS to.
This is going away because copying headers messes up the error messages, and
may lead to people editing those headers instead of the correct ones. It also
makes it easier to do bad layering in the system, which we want to avoid. We
also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any
headers.
LOCAL_C_INCLUDES
Additional directories to instruct the C/C++ compilers to look for header
files in. These paths are rooted at the top of the tree. Use
LOCAL_PATH if you have subdirectories of your own that you
want in the include paths. For example:
You should not add subdirectories of include to
LOCAL_C_INCLUDES, instead you should reference those files
in the #include statement with their subdirectories. For
example:
#include <utils/KeyedVector.h>
not #include <KeyedVector.h>
There are some components that are doing this wrong, and should be cleaned
up.
LOCAL_MODULE_TAGS
Set LOCAL_MODULE_TAGS to any number of whitespace-separated
tags. If the tag list is empty or contains droid, the module
will get installed as part of a make droid. Modules with the tag
shell_$(TARGET_SHELL) will also be installed. Otherwise, it will
only get installed by running make <your-module>
or with the make all pseudotarget.
LOCAL_REQUIRED_MODULES
Set LOCAL_REQUIRED_MODULES to any number of whitespace-separated
module names, like "libblah" or "Email". If this module is installed, all
of the modules that it requires will be installed as well. This can be
used to, e.g., ensure that necessary shared libraries or providers are
installed when a given app is installed.
LOCAL_FORCE_STATIC_EXECUTABLE
If your executable should be linked statically, set
LOCAL_FORCE_STATIC_EXECUTABLE:=true. There is a very short
list of libraries that we have in static form (currently only libc). This is
really only used for executables in /sbin on the root filesystem.
LOCAL_GENERATED_SOURCES
Files that you add to LOCAL_GENERATED_SOURCES will be
automatically generated and then linked in when your module is built.
See the Custom Tools template makefile for an
example.
LOCAL_JAVACFLAGS
If you have additional flags to pass into the javac compiler, add
them here. For example:
LOCAL_JAVACFLAGS += -Xlint:deprecation
LOCAL_JAVA_LIBRARIES
When linking Java apps and libraries, LOCAL_JAVA_LIBRARIES
specifies which sets of java classes to include. Currently there are
two of these: core and framework.
In most cases, it will look like this:
LOCAL_JAVA_LIBRARIES := core framework
Note that setting LOCAL_JAVA_LIBRARIES is not necessary
(and is not allowed) when building an APK with
"include $(BUILD_PACKAGE)". The appropriate libraries
will be included automatically.
LOCAL_LDFLAGS
You can pass additional flags to the linker by setting
LOCAL_LDFLAGS. Keep in mind that the order of parameters is
very important to ld, so test whatever you do on all platforms.
LOCAL_LDLIBS
LOCAL_LDLIBS allows you to specify additional libraries
that are not part of the build for your executable or library. Specify
the libraries you want in -lxxx format; they're passed directly to the
link line. However, keep in mind that there will be no dependency generated
for these libraries. It's most useful in simulator builds where you want
to use a library preinstalled on the host. The linker (ld) is a particularly
fussy beast, so it's sometimes necessary to pass other flags here if you're
doing something sneaky. Some examples:
If your package doesn't have a manifest (AndroidManifest.xml), then
set LOCAL_NO_MANIFEST:=true. The common resources package
does this.
LOCAL_PACKAGE_NAME
LOCAL_PACKAGE_NAME is the name of an app. For example,
Dialer, Contacts, etc. This will probably change or go away when we switch
to an ant-based build system for the apps.
LOCAL_PATH
The directory your Android.mk file is in. You can set it by putting the
following as the first line in your Android.mk:
LOCAL_PATH := $(my-dir)
The my-dir macro uses the
MAKEFILE_LIST
variable, so you must call it before you include any other makefiles. Also,
consider that any subdirectories you inlcude might reset LOCAL_PATH, so do your
own stuff before you include them. This also means that if you try to write
several include lines that reference LOCAL_PATH,
it won't work, because those included makefiles might reset LOCAL_PATH.
LOCAL_POST_PROCESS_COMMAND
For host executables, you can specify a command to run on the module
after it's been linked. You might have to go through some contortions
to get variables right because of early or late variable evaluation:
When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to
executables that you want copied. They're located automatically into the
right bin directory.
LOCAL_PREBUILT_LIBS
When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to
libraries that you want copied. They're located automatically into the
right lib directory.
LOCAL_SHARED_LIBRARIES
These are the libraries you directly link against. You don't need to
pass transitively included libraries. Specify the name without the suffix:
The build system looks at LOCAL_SRC_FILES to know what source
files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows
how to correctly do the intermediate .h and .c/.cpp files automatically. If
the files are in a subdirectory of the one containing the Android.mk, prefix
them with the directory name:
LOCAL_SRC_FILES := \
file1.cpp \
dir/file2.cpp
LOCAL_STATIC_LIBRARIES
These are the static libraries that you want to include in your module.
Mostly, we use shared libraries, but there are a couple of places, like
executables in sbin and host executables where we use static libraries instead.
LOCAL_STATIC_LIBRARIES := \
libutils \
libtinyxml
LOCAL_MODULE
LOCAL_MODULE is the name of what's supposed to be generated
from your Android.mk. For exmample, for libkjs, the LOCAL_MODULE
is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll).
For app modules, use LOCAL_PACKAGE_NAME instead of
LOCAL_MODULE. We're planning on switching to ant for the apps,
so this might become moot.
LOCAL_MODULE_PATH
Instructs the build system to put the module somewhere other than what's
normal for its type. If you override this, make sure you also set
LOCAL_UNSTRIPPED_PATH if it's an executable or a shared library
so the unstripped binary has somewhere to go. An error will occur if you forget
to.
Instructs the build system to put the unstripped version of the module
somewhere other than what's normal for its type. Usually, you override this
because you overrode LOCAL_MODULE_PATH for an executable or a
shared library. If you overrode LOCAL_MODULE_PATH, but not
LOCAL_UNSTRIPPED_PATH, an error will occur.
These are the static libraries that you want to include in your module without allowing
the linker to remove dead code from them. This is mostly useful if you want to add a static library
to a shared library and have the static library's content exposed from the shared library.
Any flags to pass to invocations of yacc for your module. A known limitation
here is that the flags will be the same for all invocations of YACC for your
module. This can be fixed. If you ever need it to be, just ask.
LOCAL_YACCFLAGS := -p kjsyy
Implementation Details
You should never have to touch anything in the config directory unless
you're adding a new platform, new tools, or adding new features to the
build system. In general, please consult with the build system owner(s)
(android-build-team) before you go
mucking around in here. That said, here are some notes on what's going on
under the hood.
Environment Setup / buildspec.mk Versioning
In order to make easier for people when the build system changes, when
it is necessary to make changes to buildspec.mk or to rerun the environment
setup scripts, they contain a version number in the variable
BUILD_ENV_SEQUENCE_NUMBER. If this variable does not match what the build
system expects, it fails printing an error message explaining what happened.
If you make a change that requires an update, you need to update two places
so this message will be printed.
In config/envsetup.make, increment the
CORRECT_BUILD_ENV_SEQUENCE_NUMBER definition.
In buildspec.mk.default, update the BUILD_ENV_SEQUENCE_DUMBER
definition to match the one in config/envsetup.make
The scripts automatically get the value from the build system, so they will
trigger the warning as well.
Additional makefile variables
You probably shouldn't use these variables. Please consult
android-build-team before using them.
These are mostly there for workarounds for other issues, or things that aren't
completely done right.
LOCAL_ADDITIONAL_DEPENDENCIES
If your module needs to depend on anything else that
isn't actually built in to it, you can add those make targets to
LOCAL_ADDITIONAL_DEPENDENCIES. Usually this is a workaround
for some other dependency that isn't created automatically.
LOCAL_BUILT_MODULE
When a module is built, the module is created in an intermediate
directory then copied to its final location. LOCAL_BUILT_MODULE is
the full path to the intermediate file. See LOCAL_INSTALLED_MODULE
for the path to the final installed location of the module.
LOCAL_HOST
Set by the host_xxx.make includes to tell base_rules.make and the other
includes that we're building for the host. Kenneth did this as part of
openbinder, and I would like to clean it up so the rules, includes and
definitions aren't duplicated for host and target.
LOCAL_INSTALLED_MODULE
The fully qualified path name of the final location of the module.
See LOCAL_BUILT_MODULE for the location of the intermediate file that
the make rules should actually be constructing.
LOCAL_REPLACE_VARS
Used in some stuff remaining from the openbinder for building scripts
with particular values set,
LOCAL_SCRIPTS
Used in some stuff remaining from the openbinder build system that we
might find handy some day.
LOCAL_MODULE_CLASS
Which kind of module this is. This variable is used to construct other
variable names used to locate the modules. See base_rules.make and
envsetup.make.
LOCAL_MODULE_NAME
Set to the leaf name of the LOCAL_BUILT_MODULE. I'm not sure,
but it looks like it's just used in the WHO_AM_I variable to identify
in the pretty printing what's being built.
LOCAL_MODULE_SUFFIX
The suffix that will be appended to LOCAL_MODULE to form
LOCAL_MODULE_NAME. For example, .so, .a, .dylib.
LOCAL_STRIP_MODULE
Calculated in base_rules.make to determine if this module should actually
be stripped or not, based on whether LOCAL_STRIPPABLE_MODULE
is set, and whether the combo is configured to ever strip modules. With
Iliyan's stripping tool, this might change.
LOCAL_STRIPPABLE_MODULE
Set by the include makefiles if that type of module is strippable.
Executables and shared libraries are.
LOCAL_SYSTEM_SHARED_LIBRARIES
Used while building the base libraries: libc, libm, libdl. Usually
it should be set to "none," as it is in $(CLEAR_VARS). When building
these libraries, it's set to the ones they link against. For example,
libc, libstdc++ and libdl don't link against anything, and libm links against
libc. Normally, when the value is none, these libraries are automatically
linked in to executables and libraries, so you don't need to specify them
manually.
