Linux上使用vcpkg + CMake配置cpprest-Toy模板网

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vcpkg的使用在Linux平台与Windows平台没什么差异，就不过多阐述。

有一点需要注意的是，Windows上安装的包默认是x86，而Linux上默认是x64。

vcpkg安装cpprest

cpprest库依赖很多库，比如boost，openssl等，但不用操心，vcpkg会帮我们自带安装。

./vcpkg install cpprestsdk

问题

需要注意的是，安装过程很有可能会失败，除网络原因外，还有一个地方会出错：

CMake Error at scripts/cmake/vcpkg_execute_build_process.cmake:134 (message):
    Command failed: /home/vcpkg/downloads/tools/cmake-3.25.1-linux/cmake-3.25.1-linux-x86_64/bin/cmake --build . --config Debug --target install -- -v -j3
    Working Directory: /home/vcpkg/buildtrees/openssl/x64-linux-dbg
    See logs for more information:
      /home/vcpkg/buildtrees/openssl/install-x64-linux-dbg-out.log

Call Stack (most recent call first):
  installed/x64-linux/share/vcpkg-cmake/vcpkg_cmake_build.cmake:74 (vcpkg_execute_build_process)
  installed/x64-linux/share/vcpkg-cmake/vcpkg_cmake_install.cmake:16 (vcpkg_cmake_build)
  ports/openssl/unix/portfile.cmake:21 (vcpkg_cmake_install)
  ports/openssl/portfile.cmake:33 (include)
  scripts/ports.cmake:147 (include)


error: building openssl:x64-linux failed with: BUILD_FAILED
error: Please ensure you're using the latest port files with `git pull` and `vcpkg update`.
Then check for known issues at:
    https://github.com/microsoft/vcpkg/issues?q=is%3Aissue+is%3Aopen+in%3Atitle+openssl
You can submit a new issue at:
    https://github.com/microsoft/vcpkg/issues/new?template=report-package-build-failure.md&title=[openssl]+Build+error
Include '[openssl] Build error' in your bug report title, the following version information in your bug description, and attach any relevant failure logs from above.
    vcpkg-tool version: 2023-01-24-8a88d63f241d391772fbde69af9cab96c3c64c75
    vcpkg-scripts version: 91dd61bd4 2023-01-27 (2 days ago)

通过查看/home/vcpkg/buildtrees/openssl/install-x64-linux-dbg-out.log日志可以发现

[1/3] cd /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean && export PATH=/bin:/opt/rh/devtoolset-8/root/usr/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/bin:/home/Listening/vcpkg/downloads/tools/ninja/1.10.2-linux && export CC=/opt/rh/devtoolset-8/root/usr/bin/cc && export AR=/opt/rh/devtoolset-8/root/usr/bin/ar && export LD=/opt/rh/devtoolset-8/root/usr/bin/ld && export RANLIB=/opt/rh/devtoolset-8/root/usr/bin/ranlib && export MAKE=/bin/make && export MAKEDEPPROG=/opt/rh/devtoolset-8/root/usr/bin/cc && export WINDRES= && /bin/perl Configure no-shared no-module enable-static-engine no-zlib no-ssl2 no-idea no-cast no-seed no-md2 no-tests linux-x86_64 --prefix=/home/Listening/vcpkg/packages/openssl_x64-linux/debug --libdir=/home/Listening/vcpkg/packages/openssl_x64-linux/debug/lib --openssldir=/etc/ssl "-fPIC -g" && /home/Listening/vcpkg/downloads/tools/cmake-3.25.1-linux/cmake-3.25.1-linux-x86_64/bin/cmake -DDIR=/home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean -P /home/Listening/vcpkg/ports/openssl/unix/remove-deps.cmake
FAILED: nssl-3.0.7-96d825e305.clean/Makefile /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean/Makefile 
cd /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean && export PATH=/bin:/opt/rh/devtoolset-8/root/usr/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/bin:/home/Listening/vcpkg/downloads/tools/ninja/1.10.2-linux && export CC=/opt/rh/devtoolset-8/root/usr/bin/cc && export AR=/opt/rh/devtoolset-8/root/usr/bin/ar && export LD=/opt/rh/devtoolset-8/root/usr/bin/ld && export RANLIB=/opt/rh/devtoolset-8/root/usr/bin/ranlib && export MAKE=/bin/make && export MAKEDEPPROG=/opt/rh/devtoolset-8/root/usr/bin/cc && export WINDRES= && /bin/perl Configure no-shared no-module enable-static-engine no-zlib no-ssl2 no-idea no-cast no-seed no-md2 no-tests linux-x86_64 --prefix=/home/Listening/vcpkg/packages/openssl_x64-linux/debug --libdir=/home/Listening/vcpkg/packages/openssl_x64-linux/debug/lib --openssldir=/etc/ssl "-fPIC -g" && /home/Listening/vcpkg/downloads/tools/cmake-3.25.1-linux/cmake-3.25.1-linux-x86_64/bin/cmake -DDIR=/home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean -P /home/Listening/vcpkg/ports/openssl/unix/remove-deps.cmake
Can't locate IPC/Cmd.pm in @INC (@INC contains: /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean/util/perl /opt/rh/devtoolset-8/root//usr/lib64/perl5/vendor_perl /opt/rh/devtoolset-8/root/usr/lib/perl5 /opt/rh/devtoolset-8/root//usr/share/perl5/vendor_perl /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 . /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean/external/perl/Text-Template-1.56/lib) at /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean/util/perl/OpenSSL/config.pm line 19.
BEGIN failed--compilation aborted at /home/Listening/vcpkg/buildtrees/openssl/x64-linux-dbg/nssl-3.0.7-96d825e305.clean/util/perl/OpenSSL/config.pm line 19.
Compilation failed in require at Configure line 23.
BEGIN failed--compilation aborted at Configure line 23.
ninja: build stopped: subcommand failed.

里面有个关键词Can't locate IPC/Cmd.pm说明在编译OpenSSL时，需要的Perl模块 IPC::Cmd 没有安装。

解决

Perl模块 IPC::Cmd 没有安装，需要安装CPAN模块，再安装IPC::Cmd

在Linux或Unix系统中，通常可以使用包管理器安装CPAN模块。比如，在Debian或Ubuntu上，使用以下命令安装CPAN：

sudo apt-get install cpanminus

如果在其他系统上，查找与您的系统相对应的包管理器命令。比如我这里是CentOS 7系统：

sudo yum install perl-CPAN

安装完后，使用以下命令安装所需的模块：

cpanm IPC::Cmd //Debian或Ubuntu

cpan IPC::Cmd // CentOS

CMake使用cpprest

CMake中使用vcpkg安装的包，需要注意几点：

CMakeLists.txt文件中设置vcpkg的root目录，且需要在project()语句之前
cpprest配置文件路径

cmake_minimum_required(VERSION 3.20)

# 设置VCPKG_ROOT所在的位置
set(VCPKG_ROOT "home/vcpkg/scripts/buildsystems/vcpkg.cmake" CACHE PATH "")
set(CMAKE_TOOLCHAIN_FILE ${VCPKG_ROOT})

project(demo)

set(CMAKE_CXX_STANDARD 14)
# 设置cppresst库所在路径
set(cpprest_DIR "/home/vcpkg/installed/x64-linux/share/cpprestsdk")
find_package(cpprestsdk CONFIG REQUIRED)

add_executable(demo main.cpp)

target_link_libraries(demo PRIVATE pthread cpprestsdk::cpprest)

通过CMake + vcpkg有个好处就是不用手写cpprest所依赖的库，不然target_link_libraries还得加上boost、openssl等。

接下来，就可以使用cpprest库了：

//main.cpp
#include <iostream>
#include <string>
#include "cpprest/http_client.h"
#include "cpprest/uri_builder.h"
#include "cpprest/http_msg.h"
#include "pplx/pplxtasks.h"
#include "cpprest/json.h"
#include "cpprest/uri.h"


using namespace web;
using namespace web::http;
using namespace web::http::client;
using namespace web::json;

std::string send_request(const std::string &url, const std::string& arg) {
    web::http::client::http_client client(url);
    // Build request URI and start the request.
    uri_builder builder(arg);

    std::string re{};
    client.request(methods::GET, builder.to_string())
                    // continue when the response is available
            .then([](http_response response) -> pplx::task<web::json::value> {
                // if the status is OK extract the body of the response into a JSON value
                // works only when the content type is application\json
                if(response.status_code() == status_codes::OK) {
                    return response.extract_json();
                }

                // return an empty JSON value
                return pplx::task_from_result(web::json::value());
            })
                    // continue when the JSON value is available
            .then([&re](pplx::task<web::json::value> previousTask) {
                // get the JSON value from the task and display content from it
                try {
//                    web::json::value const& v = previousTask.get();
                    re = previousTask.get().serialize();
                } catch (http_exception const & e) {
                    printf("Error exception:%s\n", e.what());
                }
            })
            .wait();
    return re;
}

int main()
{
    std::string url{"http://10.2.3.4:2345"};
    std::string arg{"api/storage/service-alarm-info/"};
    auto result = send_request(url,arg);
    std::cout<<result<<"\n";

    while (1)
    {
        /* code */
    }
    
    return 0;
}