未找到入口点，Android .so 文件

Question

我正在尝试将一些已编译的 C 代码合并到 Android 应用程序中。我已经能够使用 NDK 构建源代码，它生成了一个 .so（7kB）和一个 .a（近 2MB）。

我正在使用 Xamarin，所有说明都说要在项目中包含 .so。我已经完成了，应用程序加载了库。但是，它会引发 EntryPointNotFoundException 异常。这并不让我感到惊讶，因为 .so 除了 RTL 支持函数之外什么都不包含。实际代码在 .a 中。

所以我有两个问题： 1. 如何将 .a 链接到我的 Android 库中？ 要么 2. 如何让 NDK 将所有内容打包成一个 .so？

For what it's worth here is the .mk file:

ROOT := $(call my-dir)

# Build libopus
LOCAL_PATH          := ../opus-1.2.1/opus-1.2.1
include $(CLEAR_VARS)
#include the .mk files
include $(LOCAL_PATH)/celt_sources.mk
include $(LOCAL_PATH)/silk_sources.mk
include $(LOCAL_PATH)/opus_sources.mk

LOCAL_MODULE        := opus

#fixed point sources
SILK_SOURCES += $(SILK_SOURCES_FIXED)

#floating point sources - this throws badly!
#SILK_SOURCES += $(SILK_SOURCES_FLOAT)

#ARM build
CELT_SOURCES += $(CELT_SOURCES_ARM)
SILK_SOURCES += $(SILK_SOURCES_ARM)
LOCAL_SRC_FILES     := \
$(CELT_SOURCES) $(SILK_SOURCES) $(OPUS_SOURCES)

LOCAL_LDLIBS        := -lm -llog


LOCAL_C_INCLUDES    := \
$(LOCAL_PATH)/include \
$(LOCAL_PATH)/silk \
$(LOCAL_PATH)/silk/float \
$(LOCAL_PATH)/celt

LOCAL_CFLAGS        := -DNULL=0 -DSOCKLEN_T=socklen_t -DLOCALE_NOT_USED -D_LARGEFILE_SOURCE=1 -D_FILE_OFFSET_BITS=64
#LOCAL_CFLAGS        += -Drestrict='' -D__EMX__ -DOPUS_BUILD -DFIXED_POINT=1 -DDISABLE_FLOAT_API -DUSE_ALLOCA -DHAVE_LRINT -DHAVE_LRINTF -O3 -fno-math-errno
LOCAL_CFLAGS        += -Drestrict='' -D__EMX__ -DOPUS_BUILD -DUSE_ALLOCA -DHAVE_LRINT -DHAVE_LRINTF -O3 -fno-math-errno
LOCAL_CPPFLAGS      := -DBSD=1
LOCAL_CPPFLAGS      += -ffast-math -O3 -funroll-loops

#include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := opus-share
#LOCAL_SRC_FILES := libopus.a
LOCAL_STATIC_LIBRARIES := opus
include $(BUILD_SHARED_LIBRARY)

谢谢。

Answer 1

我可以确认更改为 LOCAL_WHOLE_STATIC_LIBRARIES 确实是解决方案。原始的 mk 也试图既是定点的又是浮点的。所以最终解决这一切：

# This .mk has to be in a folder called jni. Because :(
ROOT := $(call my-dir)

# Build libopus.a (static library)
LOCAL_PATH          := ../opus-1.2.1/opus-1.2.1
include $(CLEAR_VARS)
#include the .mk files
include $(LOCAL_PATH)/celt_sources.mk
include $(LOCAL_PATH)/silk_sources.mk
include $(LOCAL_PATH)/opus_sources.mk

LOCAL_MODULE        := opus

#fixed point sources
SILK_SOURCES += $(SILK_SOURCES_FIXED)

#floating point sources - this throws badly!
#SILK_SOURCES += $(SILK_SOURCES_FLOAT)

#ARM build
CELT_SOURCES += $(CELT_SOURCES_ARM)
SILK_SOURCES += $(SILK_SOURCES_ARM)
LOCAL_SRC_FILES     := \
$(CELT_SOURCES) $(SILK_SOURCES) $(OPUS_SOURCES)

LOCAL_LDLIBS        := -lm -llog

LOCAL_C_INCLUDES    := \
$(LOCAL_PATH)/include \
$(LOCAL_PATH)/silk \
$(LOCAL_PATH)/silk/fixed \
$(LOCAL_PATH)/celt

LOCAL_CFLAGS        := -DNULL=0 -DSOCKLEN_T=socklen_t -DLOCALE_NOT_USED -D_LARGEFILE_SOURCE=1 -D_FILE_OFFSET_BITS=64
LOCAL_CFLAGS        += -Drestrict='' -D__EMX__ -DOPUS_BUILD -DFIXED_POINT=1 -DDISABLE_FLOAT_API -DUSE_ALLOCA -DHAVE_LRINT -DHAVE_LRINTF -O3 -fno-math-errno
#LOCAL_CFLAGS        += -Drestrict='' -D__EMX__ -DOPUS_BUILD -DUSE_ALLOCA -DHAVE_LRINT -DHAVE_LRINTF -O3 -fno-math-errno
LOCAL_CPPFLAGS      := -DBSD=1
LOCAL_CPPFLAGS      += -ffast-math -O3 -funroll-loops

include $(BUILD_STATIC_LIBRARY)

# Now create a dynamic library that contains the static library
include $(CLEAR_VARS)
LOCAL_MODULE    := opus-share
#LOCAL_SRC_FILES := opus
LOCAL_WHOLE_STATIC_LIBRARIES := opus
include $(BUILD_SHARED_LIBRARY)

这是使用 Windows NDK 构建的，我必须将该文件（称为 Android.mk）放入名为“JNI”的目录中。可能有一些技巧可以避免涉及环境变量的操作，但我放弃了尝试它。将其与 opus 1.2.1 source code 和平台特定的 mk 文件结合起来，如下所示：

APP_ABI := arm64-v8a
APP_PLATFORM := android-19
APP_STL := c++_static
APP_BUILD_SCRIPT := Android.mk

并且您拥有适用于 Android 的 .so 文件。只需适当更改 ABI 值即可。