我们也说说Android.mk(6)

https://yq.aliyun.com/articles/27602?spm=5176.100239.blogcont37401.12.bl6Pwq

摘要： 前面基础知识已经准备得差不多了，我们开始看几个例子巩固一下

我们也说说Android.mk(6) - 案例教程

userdata是如何生成的

我们先看看userdataimage的伪目标是如何定义的：

.PHONY: userdataimageuserdataimage: $(INSTALLED_USERDATAIMAGE_TARGET)ifneq (,$(filter userdataimage, $(MAKECMDGOALS)))$(call dist-for-goals, userdataimage, $(BUILT_USERDATAIMAGE_TARGET))endif.PHONY: userdatatarballuserdatatarball: $(INSTALLED_USERDATATARBALL_TARGET)

INSTALLED_USERDATAIMAGE_TARGET

userdataimage依赖于INSTALLED_USERDATAIMAGE_TARGET，我们再看看INSTALLED_USERDATAIMAGE_TARGET是什么：

INSTALLED_USERDATAIMAGE_TARGET := $(BUILT_USERDATAIMAGE_TARGET)

BUILT_USERDATAIMAGE_TARGET

我们再继续看BUILT_USERDATAIMAGE_TARGET:

BUILT_USERDATAIMAGE_TARGET := $(PRODUCT_OUT)/userdata.img

OK，这一支明白了，就是userdata.img嘛。

# A global variable to remember all dist'ed src:dst pairs.# So if a src:dst is already dist'ed by another goal,# we should just establish the dependency and don't really call the# copy-one-dist-file to avoid multiple rules for the same target._all_dist_src_dst_pairs :=# Other parts of the system should use this function to associate# certain files with certain goals.  When those goals are built# and "dist" is specified, the marked files will be copied to DIST_DIR.## $(1): a list of goals  (e.g. droid, sdk, pdk, ndk)# $(2): the dist files to add to those goals.  If the file contains ':',#       the text following the colon is the name that the file is copied#       to under the dist directory.  Subdirs are ok, and will be created#       at copy time if necessary.define dist-for-goals$(foreach file,$(2), \  $(eval fw := $(subst :,$(space),$(file))) \  $(eval src := $(word 1,$(fw))) \  $(eval dst := $(word 2,$(fw))) \  $(eval dst := $(if $(dst),$(dst),$(notdir $(src)))) \  $(if $(filter $(_all_dist_src_dst_pairs),$(src):$(dst)),\    $(eval $(call add-dependency,$(1),$(DIST_DIR)/$(dst))),\    $(eval $(call copy-one-dist-file,\      $(src),$(DIST_DIR)/$(dst),$(1)))\      $(eval _all_dist_src_dst_pairs += $(src):$(dst))\  )\)endef

userdata的中间文件

我们再来看看userdata的中间文件是如何生成的：

userdataimage_intermediates := \    $(call intermediates-dir-for,PACKAGING,userdata)

这个好，直接调用一个函数。所谓函数，就是一个大宏，我们看看它是如何定义的：

############################################################# The intermediates directory.  Where object files go for## a given target.  We could technically get away without## the "_intermediates" suffix on the directory, but it's## nice to be able to grep for that string to find out if## anyone's abusing the system.############################################################ $(1): target class, like "APPS"# $(2): target name, like "NotePad"# $(3): if non-empty, this is a HOST target.# $(4): if non-empty, force the intermediates to be COMMON# $(5): if non-empty, force the intermedistes to be for the 2nd archdefine intermediates-dir-for$(strip \    $(eval _idfClass := $(strip $(1))) \    $(if $(_idfClass),, \        $(error $(LOCAL_PATH): Class not defined in call to intermediates-dir-for)) \    $(eval _idfName := $(strip $(2))) \    $(if $(_idfName),, \        $(error $(LOCAL_PATH): Name not defined in call to intermediates-dir-for)) \    $(eval _idfPrefix := $(if $(strip $(3)),HOST,TARGET)) \    $(eval _idf2ndArchPrefix := $(if $(strip $(5)),$(TARGET_2ND_ARCH_VAR_PREFIX))) \    $(if $(filter $(_idfPrefix)-$(_idfClass),$(COMMON_MODULE_CLASSES))$(4), \        $(eval _idfIntBase := $($(_idfPrefix)_OUT_COMMON_INTERMEDIATES)) \      ,$(if $(filter $(_idfClass),SHARED_LIBRARIES STATIC_LIBRARIES EXECUTABLES GYP),\          $(eval _idfIntBase := $($(_idf2ndArchPrefix)$(_idfPrefix)_OUT_INTERMEDIATES)) \       ,$(eval _idfIntBase := $($(_idfPrefix)_OUT_INTERMEDIATES)) \       ) \     ) \    $(_idfIntBase)/$(_idfClass)/$(_idfName)_intermediates \)endef

虽然逻辑并不是一目了然，但是所用的特性，我们前面都讲过了。

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