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虽然编译成功了，但是还是有一些不妥的地方，参考一下就行了。

比如库的版本选择就有待商榷，我这里不是按照项目作者的要求严格用对应的版本编译的，这里也可以注意一下。

编译依赖库asio

下载地址, 更正一下，我其实用的是1.13  GitHub - chriskohlhoff/asio at asio-1-12-0https://github.com/chriskohlhoff/asio/tree/asio-1-12-0https://github.com/chriskohlhoff/asio/tree/asio-1-12-0

编译命令

  ./autogen.sh

./configure  --host=arm-buildroot-linux-gnueabihf  --prefix=/home/book/test/asio-asio-1-13-0/asio/install

make 

make install

编译 openssl

下载地址 GitHub - openssl/openssl at OpenSSL_1_1_1lhttps://github.com/openssl/openssl/tree/OpenSSL_1_1_1lhttps://github.com/openssl/openssl/tree/OpenSSL_1_1_1l

编译：

./config no-asm shared no-async --prefix=${inst_dir}  --cross-complie-prefix=arm-buildroot-linux-gnueabihf-

删除makefile 中的 -m64

make 

make install

编译我们的主角 asio-dtls

下载地址：

GitHub - openssl/openssl at OpenSSL_1_1_1lhttps://github.com/openssl/openssl/tree/OpenSSL_1_1_1lhttps://github.com/sdamm/asio_dtls/tree/asio_dtls_1.12.0.0

要修改CMakeLists.txt 才能编译过：

贴出来：

cmake_minimum_required (VERSION 3.2)
project(asio_dtls)
set(OPENSSL_ROOT_DIR  /home/book/test/openssl-OpenSSL_1_1_1l/install)
include_directories(/home/book/test/asio-asio-1-13-0/asio/install/include)

find_program(
  CLANG_TIDY_EXE
  NAMES "clang-tidy"
  DOC "Path to clang-tidy executable"
  )
if(NOT CLANG_TIDY_EXE)
  message(STATUS "clang-tidy not found.")
else()
  message(STATUS "clang-tidy found: ${CLANG_TIDY_EXE}")
  set(DO_CLANG_TIDY "${CLANG_TIDY_EXE}" "-checks=*,-fuchsia-*,-google-runtime-references")

  set(CMAKE_CXX_CLANG_TIDY ${DO_CLANG_TIDY})
endif()

message(STATUS "The value of CMAKE_MODULE_PATH is: ${CMAKE_MODULE_PATH}")
find_package(OpenSSL REQUIRED)

set(THREADS_PREFER_PTHREAD_FLAG ON)
find_package(Threads REQUIRED)
set(asio_header_dir "/home/book/test/asio/asio/install/include" CACHE PATH "Path to the asio library used.")
add_library(asio INTERFACE)
target_include_directories(asio INTERFACE asio_header_dir)

add_library(asio_dtls INTERFACE)
target_include_directories(asio_dtls INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/include)
target_compile_definitions(asio_dtls INTERFACE ASIO_HEADER_ONLY)
target_link_libraries(asio_dtls INTERFACE OpenSSL::SSL OpenSSL::Crypto Threads::Threads)

set(asio_dtls_sources
    include/asio/ssl/dtls/impl/context.ipp
    include/asio/ssl/dtls/detail/impl/engine.ipp)

set(ASIO_DTLS_PUBLIC_HEADERS
    asio/dtls.hpp
    asio/ssl/dtls/acceptor.hpp
    asio/ssl/dtls/context.hpp
    asio/ssl/dtls/default_cookie_generator.hpp
    asio/ssl/dtls/socket.hpp
    )

option(asio_build_dtls_static "Build asio_dtls as static library" OFF)
if(asio_build_dtls_static)
  add_library(asio_dtls_static STATIC ${asio_dtls_sources})
  target_include_directories(asio_dtls_static PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
  target_link_libraries(asio_dtls_static OpenSSL::SSL OpenSSL::Crypto Threads::Threads)
endif(asio_build_dtls_static)

message(STATUS "CMAKE_CURRENT_SOURCE_DIR=${CMAKE_CURRENT_SOURCE_DIR}")

set(THREADS_PTHREAD_LIB "pthread")
message(STATUS "CMAKE_THREAD_LIBS_INIT=${CMAKE_THREAD_LIBS_INIT}")
option(asio_build_dtls_shared "Build asio_dtls as shared library" ON)
if(asio_build_dtls_shared)
  add_library(asio_dtls_shared SHARED ${asio_dtls_sources})
  set_target_properties(asio_dtls_shared PROPERTIES LINKER_LANGUAGE CXX)
  target_include_directories(asio_dtls_shared PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
  target_link_libraries(asio_dtls_shared OpenSSL::SSL OpenSSL::Crypto Threads::Threads)
endif(asio_build_dtls_shared)

#add_subdirectory(src)

这里测试程序没有编译过，大概是因为测试程序用到了boost，但是我并没有编译boost.

下面展示的是Toolchain.cmake

# Toolchain.cmake
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)

set(CMAKE_C_COMPILER  arm-buildroot-linux-gnueabihf-gcc)
set(CMAKE_CXX_COMPILER arm-buildroot-linux-gnueabihf-g++)

编译命令：

cmake -DCMAKE_TOOLCHAIN_FILE=../Toolchain.cmake  ..

​

重要知识点：

find_package 搜索FindXXX.cmake 的默认目录是/usr/share/cmake-xxx/Modules/

set_target_properties(asio_dtls_shared PROPERTIES LINKER_LANGUAGE CXX)

豆包说：“属性设置项。LINKER_LANGUAGE 是一个属性，用于指定链接器在链接目标时使用的编程语言。CXX 表示 C++ 语言，即告诉 CMake 在链接 asio_dtls_shared 目标时使用 C++ 链接器。”

当时没写这个报了“CMake Error: CMake can not determine linker language for target: asio_dtls_shared
CMake Error: Cannot determine link language for target "asio_dtls_shared".
”错。