Android O上開始谷歌加大力度推廣使用新的soong編譯，隨之而來的影響就是原先在Android.mk文件需要轉換為Android.bp文件做編譯配置。
使用soong提供的androidmk命令可以把Android.mk文件轉換為Android.bp文件，但是對于一些復雜的mk語法，轉換的結果往往不能像原先的Android.mk那樣可以正常編譯出想要的結果。這就需要將轉換出的Android.bp做進一步的修改，以符合原來的編譯需求。
androidmk Android.mk > Android.bp
下面來說說我所遇到的dependency "..." of "..." missing variant 錯誤的解決過程:
1.Android.mk轉換成Android.bp：
原先的Android.mk中有如下配置，目的是需要將編譯出兩個版本的tinyalsa, Android版和Host版，且名稱相同。以下是Android.mk中tinyalsa的兩個版本的配置：
include $(CLEAR_VARS)
LOCAL_C_INCLUDES:= external/tinyalsa/include
LOCAL_SRC_FILES:= mixer.c pcm.c
LOCAL_MODULE := libtinyalsa
LOCAL_SHARED_LIBRARIES:= libcutils libutils liblog
LOCAL_MODULE_TAGS := optional
LOCAL_CFLAGS += -Werror
ifeq ($(strip $(NXP_SMARTPA_SUPPORT)),tfa9895)
LOCAL_CFLAGS += -DNXP_TFA9895_SUPPORT
LOCAL_C_INCLUDES+= device/vendor/msm8937/TFA9895/app/exTfa98xx/inc
LOCAL_SHARED_LIBRARIES+= libtfa9895
endif
include $(BUILD_SHARED_LIBRARY)
ifeq ($(HOST_OS), linux)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES:= external/tinyalsa/include
LOCAL_SRC_FILES:= mixer.c pcm.c
LOCAL_MODULE := libtinyalsa
LOCAL_STATIC_LIBRARIES:= libcutils libutils liblog
LOCAL_CFLAGS += -Werror
include $(BUILD_HOST_STATIC_LIBRARY)
endif
原android版tinyalsa是shared_library, host版tinyalsa是static_library, 用androidmk命令轉換成bp文件后內容如下：
cc_library_shared {
include_dirs: ["external/tinyalsa/include"] + ["device/vendor/msm8937/TFA9895/app/exTfa98xx/inc"] + ["device/vendor/msm8937/TFA9891/app/exTfa98xx/inc"],
// ANDROIDMK TRANSLATION ERROR: unsupported conditional
// ifeq ($(strip $(NXP_SMARTPA_SUPPORT)),tfa9895)
// ANDROIDMK TRANSLATION ERROR: endif from unsupported contitional
// endif
// ANDROIDMK TRANSLATION ERROR: endif from unsupported contitional
// endif
// ANDROIDMK TRANSLATION ERROR: unsupported conditional
// ifeq ($(strip $(NXP_SMARTPA_SUPPORT)),tfa9895)
srcs: [
"mixer.c",
"pcm.c",
],
name: "libtinyalsa",
shared_libs: [
"libcutils",
"libutils",
],
cflags: ["-Werror"] + ["-DNXP_TFA9895_SUPPORT"] + ["-DNXP_TFA9895_SUPPORT"],
shared_libs: ["libtfa9895"],
// ANDROIDMK TRANSLATION ERROR: endif from unsupported contitional
// endif
// ANDROIDMK TRANSLATION ERROR: endif from unsupported contitional
// endif
}
cc_library_host_static {
include_dirs: ["external/tinyalsa/include"],
srcs: [
"mixer.c",
"pcm.c",
],
name: "libtinyalsa",
static_libs: [
"libcutils",
"libutils",
],
cflags:["-Werror"],
target:{
not_linux:{
enabled:false,
},
},
}
轉換后有兩個名字相同的libtinyalsa module。
因為項目需求，在libtinyalsa Android版中添加了共享庫依賴：libtfa9895:
所以現在的庫依賴關系變為：
Android:? libtinyalsa -> libcutils, libutils,libtfa9895
Host: libtinyalsa -> libcutils, libutils
2. Android.mk轉為Android.bp之后，手動修改，刪除名字相同的多余module.
bp文件定義的一個規則是，可以定義很多種很多個module，每個module必須有一個名字，且名字必須唯一不重復。這是因為bp文件沒有判斷邏輯，不能像mk中那樣根據不同的編譯選項選擇不同的版本。
在原Android.mk中定義了兩個名字相同的tinyalsa, 一個是Android版，一個是Host版。轉成bp后，出現了兩個名字相同的tinyalsa module,一個是cc_library_shared, 一個是cc_library_host_static。而根據bp的module名字不重復規則，這種情況是不允許的，所以我們做的第一個修改是將兩個module合并為一個，然后通過**host_supported: true**使其支持host;
又因為原來的兩個module，一個為shared,一個為static，所以第二個修改是合并后的module類型為cc_library, 這樣才能同時包含shared與static兩種不同的屬性類型。
修改后的Android.bp：
cc_library {
include_dirs: ["device/vendor/msm8937/TFA9895/app/exTfa98xx/inc"],
name: "libtinyalsa",
host_supported: true,
vendor_available: true,
srcs: [
"mixer.c",
"pcm.c",
],
shared_libs: [
"libcutils",
"libutils",
"libtfa9895",
],
cflags: ["-Werror", "-Wno-macro-redefined"]+ ["-DNXP_TFA9895_SUPPORT"],
export_include_dirs: ["include"],
local_include_dirs: ["include"],
target: {
darwin: {
enabled: false,
},
},
}
下面要說的編譯錯誤就是因為在tinyplay和tinyalsa中添加了host_supported引起的：
error: external/tinyalsa/Android.bp:1:1: dependency "libtfa9895" of "libtinyalsa" missing variant:
arch:linux_x86_64, link:shared
available variants:
arch:android_arm64_armv8-a, link:shared, image:core
arch:android_arm_armv7-a-neon_cortex-a53, link:shared, image:core
從出錯信息來看，是由于libtfa9895中不支持linux_x86_64平臺的編譯。
以下是libtfa9895轉換為Android.bp后的配置：
cc_library_shared {
local_include_dirs: [
"srv/inc",
"tfa/inc",
"utl/inc",
"hal/inc",
"hal/src",
"hal/src/lxScribo",
"srv/src/iniFile",
"app/exTfa98xx/inc",
],
export_include_dirs: [
"srv/inc",
"tfa/inc",
"utl/inc",
"hal/inc",
"hal/src",
"hal/src/lxScribo",
"srv/src/iniFile",
"app/exTfa98xx/inc",
],
srcs: ["app/exTfa98xx/src/main_container.c"],
name: "libtfa9895",
shared_libs: [
"libcutils",
],
static_libs: [
"libsrv",
"libtfa",
"libhal",
],
}
?3. 除錯過程：
libtinyalsa依賴庫有三個，libcutils, libutils, libtfa9895,
而log中只提供libtfa9895有錯，查看libcutils和libutils的配置發現，這兩個庫里的配置信息都有添加host_supported，而libtfa9895沒有，所以嘗試在libtfa9895中添加host_supported配置后重新編譯，
然后出現了相同的錯誤提示，只不過這次提示libtfa9895依賴的三個庫(libsrv/libtfa/libhal)不支持host。看來在有host_supported配置的庫中，其依賴庫也必須是host_supported的。
在libsrv/libtfa/libhal中分別添加host_supported配置后，再次提示這三個庫依賴的libutils不支持host.
查看libutils的配置發現libutils有添加host_supported，這里怎么回事呢？
cc_library {
name: "libutils",
vendor_available: true,
host_supported: true,
srcs: [
....
],
cflags: ["-Werror"],
include_dirs: ["external/safe-iop/include"],
header_libs: [
"libutils_headers",
],
export_header_lib_headers: [
"libutils_headers",
],
arch: {
mips: {
cflags: ["-DALIGN_DOUBLE"],
},
},
target: {
android: {
srcs: [
"Looper.cpp",
"ProcessCallStack.cpp",
"Trace.cpp",
],
cflags: ["-fvisibility=protected"],
shared_libs: [
"libbacktrace",
"libcutils",
"libdl",
"liblog",
"libvndksupport",
],
sanitize: {
misc_undefined: ["integer"],
},
},
host: {
cflags: ["-DLIBUTILS_NATIVE=1"],
shared: {
enabled: false,
},
},
linux: {
srcs: [
"Looper.cpp",
"ProcessCallStack.cpp",
],
},
linux_bionic: {
enabled: true,
srcs: [
"Looper.cpp",
"ProcessCallStack.cpp",
],
},
darwin: {
cflags: ["-Wno-unused-parameter"],
},
// Under MinGW, ctype.h doesn't need multi-byte support
windows: {
cflags: ["-DMB_CUR_MAX=1"],
enabled: true,
},
},
clang: true,
}
仔細分析libutils中的配置，發現原來在target:下的host配置，將shared屬性設置成了false，就是說在編譯Android版時，libutils可以作為shared lib引用，但是在host版中，只能做為static lib引用。
host: {
cflags: ["-DLIBUTILS_NATIVE=1"],
shared: {
enabled: false,
},
},
所以對引用libutils的module中，做了如下修改，首先刪除libutils的引用，然后添加如下配置：
target: {
android: {
cflags: ["-DAndroid"],
shared_libs: [
"libutils",
],
},
host: {
static_libs: ["libutils"],
},
},
android版以shared lib引用libutils, host版以static lib引用。
修改后的完整的libtfa9895的配置信息如下：
cc_library_shared {
local_include_dirs: [
"srv/inc",
"tfa/inc",
"utl/inc",
"hal/inc",
"hal/src",
"hal/src/lxScribo",
"srv/src/iniFile",
"app/exTfa98xx/inc",
],
export_include_dirs: [
"srv/inc",
"tfa/inc",
"utl/inc",
"hal/inc",
"hal/src",
"hal/src/lxScribo",
"srv/src/iniFile",
"app/exTfa98xx/inc",
],
srcs: ["app/exTfa98xx/src/main_container.c"],
name: "libtfa9895",
host_supported: true,
shared_libs: [
"libcutils",
],
static_libs: [
"libsrv",
"libtfa",
"libhal",
],
target: {
android: {
cflags: ["-DAndroid"],
shared_libs: [
"libutils",
],
},
host: {
static_libs: ["libutils"],
},
},
}
所以修改完成后，編譯通過。
?4. 進一步完善
回到前面我們libtinyalsa的定義，在原mk中android版 libtinyalsa是shared library, host版是static library，而轉成bp后，libtinyalsa合并成了一個cc_library，但是并未對android版與host版區分其shared/static屬性。
參考libutils中的方法，可以對libtinyalsa? target為android與host兩個版本的shared屬性設置為不同的值。
target: {
android:{
shared:{
enabled: true,
},
},
host:{
cflags: ["-DLIBUTILS_NATIVE=1"],
shared: {
enabled: false,
},},
},
