链接预建静态库 ndk 与 Android 源

Question

我最近发现，从 ndk-build 链接预构建的静态库与从 android 源代码树 (mm) 中链接是根本不同的。这是为什么呢？

   // main.cpp
   #include <stdio.h>
   #include "doubler.hpp"

    int main()
    {
       printf("test a static lib \n");

       // library function
       doubler *p = new doubler();
       delete p;

       return 0;
    }

安卓MK：

LOCAL_PATH := $(call my-dir)

###################### static lib ##################
### prebuilt lib works in NDK but not Android src
#include $(CLEAR_VARS)
#LOCAL_MODULE := doubleIt_prebuilt
#LOCAL_SRC_FILES :=  $(LOCAL_PATH)/libDoubler.a
#LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
##LOCAL_SRC_FILES :=  libDoubler.a
#include $(PREBUILT_STATIC_LIBRARY)

###################### test app ##################
include $(CLEAR_VARS)

# binary name
LOCAL_MODULE:= testApp

# c++ file extension
LOCAL_CPP_EXTENSION := .cpp

# src files
LOCAL_SRC_FILES := main.cpp

# include dir
LOCAL_C_INCLUDES := $(LOCAL_PATH)

### this works in Android src, but not in NDK 
LOCAL_LDLIBS := -L$(LOCAL_PATH) -lDoubler

### prebuilt lib works in NDK but not Android src
#LOCAL_STATIC_LIBRARIES := doubleIt_prebuilt

#what to build
include $(BUILD_EXECUTABLE)

最终，在 src 树中链接静态库的正确方法是什么？

Answer 1

这是为什么？

ndk-build 和 AOSP 构建系统是两个完全不同的构建系统，不幸的是它们看起来非常相似。

最终，在 src 树中链接静态库的正确方法是什么？

在 AOSP 树中？预建模块的定义不同。以下是几个例子：

https://android.googlesource.com/platform/prebuilts/sdk/+/9c011b3a7784803b96dc0f0a840aa9033a0cd62a/tools/Android.mk#291

include $(CLEAR_VARS)
LOCAL_MODULE := libbcc
LOCAL_SRC_FILES := $(HOST_OS)/lib64/$(LOCAL_MODULE)$(HOST_SHLIB_SUFFIX)
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_SUFFIX := $(HOST_SHLIB_SUFFIX)
LOCAL_IS_HOST_MODULE := true
LOCAL_MULTILIB := 64
include $(BUILD_PREBUILT)

https://android.googlesource.com/platform/development/+/518e6c3a28cc63fd094c8b255e268650b03fdab5/host/windows/prebuilt/usb/Android.mk

include $(CLEAR_VARS)
LOCAL_IS_HOST_MODULE := true
LOCAL_MODULE := AdbWinApi
LOCAL_MODULE_CLASS := STATIC_LIBRARIES
LOCAL_SRC_FILES_x86 := AdbWinApi.a
LOCAL_MODULE_SUFFIX := .a
LOCAL_MULTILIB := 32
LOCAL_MODULE_HOST_OS := windows
include $(BUILD_PREBUILT)

然后，您可以像使用任何其他库一样使用它们：LOCAL_STATIC_LIBRARIES := libmyprebuilt。上述两个示例均适用于主机模块。对于目标模块，只需删除该行。

请注意，AOSP 的新（仍在进行中）构建系统 Soong 尚不支持预构建模块。这些目前只能在 Android.mk 文件中定义。