Question

我已经访问了所有其他问题，但从我看到的都不是我的问题。

在MacBook Pro 16GB内存Intel Core I7上运行OS X El Capitan 10.11.6

我也经营过酿酒医生，但没有看到任何会引起这个问题的问题。下面是我的CMakeLists.txt文件：

cmake_minimum_required(VERSION 3.0.0)
project(WebClient VERSION 0.0.0)

include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPLIER_SUPPORTS_CXX14)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPLIER_SUPPORTS_CXX0X)
if(COMPLIER_SUPPORTS_CXX14)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
elseif(COMPILER_SUPPORTS_CXX0X)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
else()
    message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++14 support.
                    Please use a different C++ compiler.")
endif()

FIND_PACKAGE( Boost 1.62 COMPONENTS program_options REQUIRED )
INCLUDE_DIRECTORIES( ${Boost_INCLUDE_DIR} )

set(OPT_CPPFLAGS "-I/usr/local/opt/openssl/include -I/usr/local/opt/libiconv/include")
set(OPT_LDFLAGS "-v -lcpprest -lboost_system -L/usr/local/opt/openssl/lib -L/usr/local/opt/libiconv/lib -lcrypto -lssl")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OPT_CPPFLAGS} -v -g -O3 -fno-common -stdlib=libc++")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OPT_LDFLAGS}")

add_executable(anyExecutable webclient.cpp)

TARGET_LINK_LIBRARIES( anyExecutable ${Boost_LIBRARIES} )

include(CPack)

我用brew来安装cpprestsdk / 2.8.0，其中还包括boost / 1.62.0和openssl / 1.0.2j以及libiconv / 1.14。我的代码来自wiki cpprestsdk的教程。

#include <cpprest/http_client.h>
#include <cpprest/filestream.h>
#include <atomic>

using namespace utility;                    // Common utilities like string conversions
using namespace web;                        // Common features like URIs.
using namespace web::http;                  // Common HTTP functionality
using namespace web::http::client;          // HTTP client features
using namespace concurrency::streams;       // Asynchronous streams

int main(int argc, char* argv[]) {
  auto fileStream = std::make_shared<ostream>();

  // Open stream to output file.
  pplx::task<void> requestTask = fstream::open_ostream( U("results.xml") ).then(
    [=](ostream outFile) {
        *fileStream = outFile;

        // Create http_client to send the request.
        http_client client(U("http://www.dictionaryapi.com/api/v1/references/"));

        // Build request URI and start the request.
        uri_builder builder(U("thesaurus/xml/"));
        builder.append_path(U("ranking"),true);
        builder.append_query(U("?key"), U("--------------------"));
        return client.request(methods::GET, builder.to_string());
  })

  // Handle response headers arriving.
  .then( [=](http_response response ) {
    printf("Received response status code:%u\n", response.status_code());

    // Write response body into the file.
    return response.body().read_to_end(fileStream->streambuf());
  })

  // Close the file stream.
  .then( [=](size_t ) {
    return fileStream->close();
  });

  // Wait for all the outstanding I/O to complete and handle any exceptions
  try {
    requestTask.wait();
  } catch (const std::exception &e) {
    printf("Error exception:%s\n", e.what());
  }//try-catch BLOCK

  return 0;
}//Main

为了节省一些空间，只能打印一些错误，但是找不到相同的错误：

    [vscode] Executing cmake command: cmake --build /Users/gumpy/git-repos/webapi/build --target all --config Debug -- -j 10
[ 50%] Building CXX object CMakeFiles/anyExecutable.dir/webclient.cpp.o
Apple LLVM version 8.0.0 (clang-800.0.38)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.11.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -disable-free -disable-llvm-verifier -discard-value-names -main-file-name webclient.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 274.1 -v -dwarf-column-info -debug-info-kind=standalone -dwarf-version=2 -debugger-tuning=lldb -coverage-file /Users/gumpy/git-repos/webapi/build/CMakeFiles/anyExecutable.dir/webclient.cpp.o -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.0.0 -I /usr/local/include -I /usr/local/opt/openssl/include -I /usr/local/opt/libiconv/include -stdlib=libc++ -O3 -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /Users/gumpy/git-repos/webapi/build -ferror-limit 19 -fmessage-length 0 -stack-protector 1 -fblocks -fobjc-runtime=macosx-10.11.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fno-common -fdiagnostics-show-option -vectorize-loops -vectorize-slp -o CMakeFiles/anyExecutable.dir/webclient.cpp.o -x c++ /Users/gumpy/git-repos/webapi/webclient.cpp
clang -cc1 version 8.0.0 (clang-800.0.38) default target x86_64-apple-darwin15.6.0
ignoring nonexistent directory "/usr/include/c++/v1"
ignoring duplicate directory "/usr/local/include"
  as it is a non-system directory that duplicates a system directory
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/opt/openssl/include
 /usr/local/opt/libiconv/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1
 /usr/local/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.0.0/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /usr/include
 /System/Library/Frameworks (framework directory)
 /Library/Frameworks (framework directory)
End of search list.
[100%] Linking CXX executable anyExecutable
Apple LLVM version 8.0.0 (clang-800.0.38)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.11.0 -o anyExecutable -L/usr/local/opt/openssl/lib -L/usr/local/opt/libiconv/lib -search_paths_first -headerpad_max_install_names -lcpprest -lboost_system -lcrypto -lssl CMakeFiles/anyExecutable.dir/webclient.cpp.o /usr/local/lib/libboost_program_options-mt.dylib -lc++ -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.0.0/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
  "boost::this_thread::interruption_point()", referenced from:
      boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) in webclient.cpp.o
      boost::condition_variable::do_wait_until(boost::unique_lock<boost::mutex>&, timespec const&) in webclient.cpp.o
  "boost::chrono::steady_clock::now()", referenced from:
      pplx::details::event_impl::wait(unsigned int) in webclient.cpp.o
  "boost::chrono::system_clock::now()", referenced from:
      pplx::details::event_impl::wait(unsigned int) in webclient.cpp.o
  "boost::detail::get_current_thread_data()", referenced from:
      boost::detail::interruption_checker::interruption_checker(_opaque_pthread_mutex_t*, _opaque_pthread_cond_t*) in webclient.cpp.o
ld: symbol(s) not found for architecture x86_64

Answer 1

缺少的符号名称是由于缺少库。必要的CPPFLAGS和LDFLAGS是：

CPPFLAGS = -stdlib=libc++
LDFLAGS = -lcpprest -lboost_system -lboost_thread-mt -lboost_chrono-mt -lssl -lcrypto

非常感谢大家的帮助。

Answer 2

看起来this可能与您的问题相同，答案与-lcrypto相关联。

编辑：您的问题是您正在尝试构建一个需要与其他“库”链接的程序 - 也就是通常预编译的其他代码片段 - 它们位于您系统的某个位置，并且它定义了“符号”，这基本上是另一种表达变量或函数名称的方式。

您可以通过在编译命令中包含表示您需要链接的内容的参数来让编译器知道您需要哪些库 - 在这种情况下，您的前几个问题因为您与-lcrypto链接而消失，从那时起你的代码能够找到之前“未定义”的“符号” - 即变量和函数名称。

对于其他问题，您添加了'lcrypto'，尝试使用this wiki中的参数在Linux上构建cpprestsdk。标志似乎是：

-lboost_system -lssl -lcpprest -lboost_chrono

最后，但并非最不重要的是，您是否按照their site?在Mac OSX上构建此软件的说明进行操作，这可能会为您节省很多痛苦！：）

编辑：添加了一些。

Answer 3

原始问题 ：

  "web::uri_builder::append_path(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool)", referenced from:
      std::__1::__function::__func<main::$_0, std::__1::allocator<main::$_0>, pplx::task<web::http::http_response> (Concurrency::streams::basic_ostream<unsigned char>)>::operator()(Concurrency::streams::basic_ostream<unsigned char>&&) in webclient.cpp.o
  "web::uri_builder::append_query(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, bool)", referenced from:
      web::uri_builder& web::uri_builder::append_query<char [37]>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const (&) [37], bool) in webclient.cpp.o
  "web::uri_builder::to_string()", referenced from:
      std::__1::__function::__func<main::$_0, std::__1::allocator<main::$_0>, pplx::task<web::http::http_response> (Concurrency::streams::basic_ostream<unsigned char>)>::operator()(Concurrency::streams::basic_ostream<unsigned char>&&) in webclient.cpp.o
  "web::uri::encode_impl(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::function<bool (int)> const&)", referenced from:
      web::uri_builder& web::uri_builder::append_query<char [37]>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const (&) [37], bool) in webclient.cpp.o
  ...

::__1是LLVM的匿名命名空间。您在上面看到的是混合和匹配运行时的症状。即，-stdlib=XXX的使用不一致。

你需要用GNU的装备和-stlib=libstdc++来构建一切;或者你需要用LLVM的装备和-stdlib=libc++来构建所有东西。

我发现最有效避免用户问题和问题的方法是始终在OS X和iOS上使用LLVM的设备。即，始终使用-stdlib=libc++。

更新了问题 ：

Undefined symbols for architecture x86_64:
  "boost::this_thread::interruption_point()", referenced from:
      boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) in webclient.cpp.o
      boost::condition_variable::do_wait_until(boost::unique_lock<boost::mutex>&, timespec const&) in webclient.cpp.o
  "boost::chrono::steady_clock::now()", referenced from:
      pplx::details::event_impl::wait(unsigned int) in webclient.cpp.o
  "boost::chrono::system_clock::now()", referenced from:
      pplx::details::event_impl::wait(unsigned int) in webclient.cpp.o
  "boost::detail::get_current_thread_data()", referenced from:
      boost::detail::interruption_checker::interruption_checker(_opaque_pthread_mutex_t*, _opaque_pthread_cond_t*) in webclient.cpp.o
ld: symbol(s) not found for architecture x86_64

有关更新的问题，请参阅Boost用户指南中的Using and building the library。你必须使用线程支持构建Boost（Brew会这么做吗？），你必须链接到Boost线程库（CMake是这么做的吗？）。

我没有使用Boost或CMake，所以我无法再接你了。对不起。

set(OPT_CPPFLAGS "-I/usr/local/opt/openssl/include -I/usr/local/opt/libiconv/include")

我不是CMake专家，但这也可能有问题。 CPPFLAGS是C预处理器的标志。它们可能会也可能不会添加到CFLAGS和CXXFLAGS。

为了以防万一，你绝对应该为CFLAGS和CXXFLAGS标注相同的标记。如果这是一个Autotools项目，那么我会将更改为必须。但就像我说的那样，我没有任何想象力的CMake专家。

最后一点说明......你不能用CMake来构建OpenSSL。你必须configure an build it yourself。安装后，您可以find-openssl.cmake类型的方式引用已安装的OpenSSL。

原因并不容易... OpenSSL的Configure脚本设置了一些在构建过程中稍后使用的重要设置。设置的两个最重要的文件是<opensslconf.h> and <bn.h>。

通过Configure enable-ec_nistp_64_gcc_128，您可以在基于Intel的x86_64机器上获得令人印象深刻的Diffie-Hellman和Elliptic Curves速度提升（2x到4x）。

cpprestsdk：体系结构的未定义符号x86_64

3 个答案: