libevent之android与鸿蒙编译过程

背景

    最近基于libevent开发了一个端侧的缓存代理库，先是基于macOS编译开发的，基本0问题，后来移植到鸿蒙与android时遇到一些编译链接问题。

    libevent版本如下：

软件版本号

libevent-2.1.8

android编译

编译环境

android studio版本	ndk编译链版本	api级别
Android Studio Flamingo | 2022.2.1 Patch 2 Build #AI-222.4459.24.2221.10121639, built on May 12, 2023 Runtime version: 17.0.6+0-17.0.6b802.4-9586694 aarch64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o. macOS 14.3.1 GC: G1 Young Generation, G1 Old Generation Memory: 2048M Cores: 10 Metal Rendering is ON Registry:     external.system.auto.import.disabled=true     ide.text.editor.with.preview.show.floating.toolbar=false     ide.instant.shutdown=false     gradle.version.catalogs.dynamic.support=true Non-Bundled Plugins:     OpenGL-Plugin (1.0.73)     Dart (222.4582)     com.localizely.flutter-intl (1.18.3-2022.2)     io.flutter (74.0.2)	~/Library/Android/sdk/ndk/22.1.7171670	28

问题现象

ld: error: undefined symbol: arc4random_addrandom
>>> referenced by evutil_rand.c
>>>               evutil_rand.o:(evutil_secure_rng_add_bytes) in archive ./.libs/libevent.a
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [sample/dns-example] Error 1
make: *** [all] Error 2
/Applications/Xcode.app/Contents/Developer/usr/bin/make  install-am
  CCLD     sample/dns-example
ld: error: undefined symbol: arc4random_addrandom
>>> referenced by evutil_rand.c
>>>               evutil_rand.o:(evutil_secure_rng_add_bytes) in archive ./.libs/libevent.a
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [sample/dns-example] Error 1
make: *** [install] Error 2

解决办法

    找到evutil_rand.c文件，将以下代码注释掉即可：

// void
// evutil_secure_rng_add_bytes(const char *buf, size_t n)
// {
// 	arc4random_addrandom((unsigned char*)buf,
// 	    n>(size_t)INT_MAX ? INT_MAX : (int)n);
// }

    贴出android下编译libevent为arm64和armv7a架构的shell脚本： 

#!/bin/bash

# 根据实际ndk编译链位置修改
export ANDROID_NDK_HOME=/Users/mingo/Library/Android/sdk/ndk/22.1.7171670
export TOOLCHAIN_DIR=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64
export SYSROOT=$TOOLCHAIN_DIR/sysroot

export TARGET_ARCH=aarch64-linux-android
export TOOLCHAIN=$TOOLCHAIN_DIR
export API_LEVEL=28
TARGET=aarch64-linux-android${API_LEVEL}

export CLANG="$TOOLCHAIN/bin/aarch64-linux-android$API_LEVEL-clang"
export CLANGXX="$TOOLCHAIN/bin/aarch64-linux-android$API_LEVEL-clang++"
export AR="$TOOLCHAIN/bin/aarch64-linux-android-ar"
export LD="$TOOLCHAIN/bin/aarch64-linux-android-ld"
export RANLIB="$TOOLCHAIN/bin/aarch64-linux-android-ranlib"
export STRIP="$TOOLCHAIN/bin/aarch64-linux-android-strip"

# 根据实际openssl位置修改
OPENSSL_OUTPUT=/Users/mingo/Applications/workspace/opensrc/openssl-android/android
OPENSSL_DIR=${OPENSSL_OUTPUT}/aarch64
PKG_CONFIG_PATH="$OPENSSL_DIR/lib/pkgconfig"

CFLAGS="--sysroot=$SYSROOT -I$OPENSSL_DIR/include --target=$TARGET -fPIC -DEVUTIL_DISABLE_ARC4RANDOM"
LDFLAGS="--sysroot=$SYSROOT -L$OPENSSL_DIR/lib -lz"

OUTPUT_DIR=$(pwd)/android/$TARGET_ARCH
mkdir -p ${OUTPUT_DIR}

function build() {
    ./configure --host=$TARGET_ARCH --prefix=$OUTPUT_DIR \
        --with-sysroot=${SYSROOT} \
        --with-openssl=$OPENSSL_DIR \
        --disable-shared \
        --disable-arc4random \
        CC=$CLANG \
        CXX=$CLANGXX \
        AR=$AR \
        RANLIB=$RANLIB \
        CFLAGS="$CFLAGS" \
        LDFLAGS="$LDFLAGS"

    make clean
    make j8
    make install
}
build

TARGET_ARCH=arm-linux-androideabi
TARGET=arm-linux-android${API_LEVEL}
OUTPUT_DIR=$(pwd)/android/$TARGET_ARCH
mkdir -p ${OUTPUT_DIR}

OPENSSL_DIR=${OPENSSL_OUTPUT}/armv7a
PKG_CONFIG_PATH="$OPENSSL_DIR/lib/pkgconfig"

CFLAGS="--sysroot=$SYSROOT -I$OPENSSL_DIR/include --target=$TARGET -fPIC -DEVUTIL_DISABLE_ARC4RANDOM"
LDFLAGS="--sysroot=$SYSROOT -L$OPENSSL_DIR/lib -lz"

build

鸿蒙编译

编译环境

DevEco版本	编译链版本	api级别
DevEco Studio NEXT Developer Beta3 Build #DS-233.14475.28.36.503600 Build Version: 5.0.3.600, built on August 7, 2024 Runtime version: 17.0.10+1-b1087.17 aarch64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o. macOS 14.3.1 GC: G1 Young Generation, G1 Old Generation Memory: 2048M Cores: 10 Metal Rendering is ON Registry:   idea.plugins.compatible.build=IC-233.14475.28	~/Library/OpenHarmony/Sdk/12	12

    先是到华为官网下载DevEco IDE开发工具，ID安装好后，再安装鸿蒙编译链，选择api 12的ndk版本进行安装：

下载中心 | 华为开发者联盟-HarmonyOS开发者官网，共建鸿蒙生态

    编译链安装完毕，本文默认安装在以下目录： 

mingo@localhost:~/Library/OpenHarmony/Sdk/12$pwd
/Users/mingo/Library/OpenHarmony/Sdk/12
mingo@localhost:~/Library/OpenHarmony/Sdk/12$tree -L 2
.
├── native
│   ├── NOTICE.txt
│   ├── build
│   ├── build-tools
│   ├── llvm
│   ├── nativeapi_syscap_config.json
│   ├── ndk_system_capability.json
│   ├── oh-uni-package.json
│   └── sysroot
└── toolchains
    ├── NOTICE.txt
    ├── ark_disasm
    ├── configcheck
    ├── diff
    ├── hdc
    ├── hnpcli
    ├── id_defined.json
    ├── idl
    ├── lib
    ├── libusb_shared.dylib
    ├── modulecheck
    ├── oh-uni-package.json
    ├── restool
    ├── syscap_tool
    └── syscapcheck

11 directories, 15 files

编译脚本 

    编译链安装完毕，便可以利用该工具链进行编译了，贴出完整编译脚本： 

#!/bin/bash

set -e

# 根据实际位置修改
HARMONY_SDK_PATH=/Users/mingo/Library/OpenHarmony/Sdk/12

CLANG=$HARMONY_SDK_PATH/native/llvm/bin/clang
CLANGXX=$HARMONY_SDK_PATH/native/llvm/bin/clang++
AR=$HARMONY_SDK_PATH/native/llvm/bin/llvm-ar
RANLIB=$HARMONY_SDK_PATH/native/llvm/bin/llvm-ranlib

# compile for aarch64
TARGET_ARCH=aarch64-linux-gnu
TARGET=aarch64-linux-ohos
SYSROOT=$HARMONY_SDK_PATH/native/sysroot

ZLIB_ROOT_PATH=${HARMONY_SDK_PATH}/native/sysroot/usr
ZLIB_INCLUDE_PATH=${ZLIB_ROOT_PATH}/include
ZLIB_LIB_PATH=${ZLIB_ROOT_PATH}/lib/aarch64-linux-ohos

# 根据实际位置修改
OPENSSL_DIR=/Users/mingo/Applications/workspace/opensrc/openssl/hmos/aarch64
PKG_CONFIG_PATH="$OPENSSL_DIR/lib/pkgconfig"
CPPFLAGS="-I$OPENSSL_DIR/include -I${ZLIB_INCLUDE_PATH}"

SYSLIB_INCLUDE_DIR=${SYSROOT}/usr/include/aarch64-linux-ohos
echo "syslib=$SYSLIB_INCLUDE_DIR"
CFLAGS="--sysroot=$SYSROOT -I$SYSLIB_INCLUDE_DIR -I$OPENSSL_DIR/include -I$ZLIB_INCLUDE_PATH --target=$TARGET -fPIC"
#CFLAGS="--sysroot=$SYSROOT -I$SYSLIB_INCLUDE_DIR -I$ZLIB_INCLUDE_PATH --target=$TARGET -fPIC"
LDFLAGS="--sysroot=$SYSROOT -L$OPENSSL_DIR/lib -L$ZLIB_LIB_PATH -lz"

export CC=$CLANG
export CXX=$CLANGXX
export AR=$AR
export RANLIB=$RANLIB
export CFLAGS=$CFLAGS
export LDFLAGS=$LDFLAGS

# compile for libevent-2.1.8-stable
LIBEVENT_SRC_PATH=`pwd`/libevent-2.1.8-stable

cd $LIBEVENT_SRC_PATH
PREFIX=${LIBEVENT_SRC_PATH}/ohos/aarch64
mkdir -p ${PREFIX}

function build_event() {
    make clean
    make distclean

    ./configure --host=$TARGET_ARCH --prefix=$PREFIX \
        --with-sysroot=${SYSLIB_INCLUDE_DIR} \
        --with-openssl=$OPENSSL_DIR \
        --with-zlib=$ZLIB_ROOT_PATH \
		--disable-shared \
        CC=$CLANG \
        CXX=$CLANGXX \
        AR=$AR \
        RANLIB=$RANLIB \
        CFLAGS="$CFLAGS" \
        LDFLAGS="$LDFLAGS"

    make verbose=1
    make install
    cd ..
}

build_event

提示：鸿蒙编译链编译libevent的时候，先是下载的api=10的编译链，但在找系统库文件的时候找不到，于是切到api=12级别的编译链，可顺利编译出所需静态库。