build option on building playwav

剛好要try alsa，所以就用 system/extra/sound/playwav 來看 target 是 sound (不是 playwav)。 touch system/extra/sound/playwav.c 看一下 build command.. prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin/arm-eabi-gcc -I system/core/include -I hardware/libhardware/include -I hardware/libhardware_legacy/include -I hardware/ril/include -I dalvik/libnativehelper/include -I frameworks/base/include -I frameworks/base/opengl/include -I external/skia/include -I out/target/product/imx51_BBG/obj/include -I bionic/libc/arch-arm/include -I bionic/libc/include -I bionic/libstdc++/include -I bionic/libc/kernel/common -I bionic/libc/kernel/arch-arm -I bionic/libm/include -I bionic/libm/include/arch/arm -I bionic/libthread_db/include -I system/extras/sound -I out/target/product/imx51_BBG/obj/EXECUTABLES/sound_intermediates -I out/target/product/imx51_BBG/obj/STATIC_LIBRARIES/libwebcore_intermediates -c -fno-exceptions -Wno-multichar -msoft-float -fpic -ffunction-sections -funwind-tables -fstack-protector -fno-short-enums -march=armv5te -mtune=xscale -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -include system/core/include/arch/linux-arm/AndroidConfig.h -I system/core/include/arch/linux-arm/ -mthumb-interwork -DANDROID -fmessage-length=0 -W -Wall -Wno-unused -Winit-self -Wpointer-arith -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -DSK_RELEASE -DNDEBUG -g -Wstrict-aliasing=2 -finline-functions -fno-inline-functions-called-once -fgcse-after-reload -frerun-cse-after-loop -frename-registers -DNDEBUG -UDEBUG -mthumb -Os -fomit-frame-pointer -fno-strict-aliasing -finline-limit=64 -MD -o out/target/product/imx51_BBG/obj/EXECUTABLES/sound_intermediates/playwav.o system/extras/sound/playwav.c 果然很麻煩... sound 的 makefile: LOCAL_PATH := $(call my-dir) // 就是 pwd include $(CLEAR_VARS) // 清掉所有變數 LOCAL_MODULE := sound // 這個 program 要用的名字 LOCAL_SRC_FILES := playwav.c LOCAL_MODULE_TAGS := optional // 屬於哪一類的 tag .. 在 make 時會指定 eng, debug, user.. include $(BUILD_EXECUTABLE) 其中LOCAL_MODULE_TAGS 是用來決定build 哪些 target 需要的變數。 像 optional 就永遠不會 build 進 system. 改為 eng 後，在ˋ build eng 時，就會 build 進去。