Docopt链接器错误示例程序

docopt linker error for example program

本文关键字：例程 程序 错误 链接 Docopt      更新时间：2023-10-16

我正试图从docopt的github页面编译示例代码。我得到一个链接错误虽然:

/tmp/test-d3ed6b.o: In function `main':
test.cpp:(.text+0xf3): undefined reference to `docopt::docopt(std::string const&, std::vector<std::string, std::allocator<std::string> > const&, bool, std::string const&, bool)'
test.cpp:(.text+0x1c8): undefined reference to `docopt::operator<<(std::ostream&, docopt::value const&)'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我有一个文件test.cpp和一个目录docopt，其中包含所有的docopt文件。

test.cpp:

#include <iostream>
#include "docopt/docopt.h"
static const char USAGE[] =
R"(Naval Fate.
Usage:
naval_fate ship new <name>...
naval_fate ship <name> move <x> <y> [--speed=<kn>]
naval_fate ship shoot <x> <y>
naval_fate mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate (-h | --help)
naval_fate --version
Options:
-h --help     Show this screen.
--version     Show version.
--speed=<kn>  Speed in knots [default: 10].
--moored      Moored (anchored) mine.
--drifting    Drifting mine.
)";
int main(int argc, const char** argv)
{
    std::map<std::string, docopt::value> args
    = docopt::docopt(USAGE,
                     { argv + 1, argv + argc },
                     true,               // show help if requested
                     "Naval Fate 2.0");  // version string
    for(auto const& arg : args) {
        std::cout << arg.first <<  arg.second << std::endl;
    }
    return 0;
}

这个错误是怎么回事?我怎样才能解决这个问题呢?我试过clang-3.5和g++

我也遇到过这种情况。

我使用cmake和CMakeLists.txt中的一些特定配置解决了这个问题。下面的配置对我有效:

cmake_minimum_required (VERSION 3.5)
project(my_project)
include(ExternalProject)
set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11" )
set(DOCOPT_ROOT ${PROJECT_SOURCE_DIR}/external/docopt)
set(DOCOPT_INCLUDE_DIRS ${DOCOPT_ROOT}/include/docopt)
set(DOCOPT_LIBRARIES ${DOCOPT_ROOT}/lib/libdocopt.a)
set(docopt_INSTALL_DIR "${DOCOPT_ROOT}")
set(docopt_CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${docopt_INSTALL_DIR})
ExternalProject_Add(docopt
  PREFIX ${DOCOPT_ROOT}
  GIT_REPOSITORY https://github.com/docopt/docopt.cpp.git
  BINARY_DIR ${DOCOPT_ROOT}
  INSTALL_DIR ${DOCOPT_ROOT}
  CMAKE_ARGS ${docopt_CMAKE_ARGS}
  LOG_DOWNLOAD ON
  LOG_CONFIGURE ON
  LOG_BUILD ON
  LOG_INSTALL ON
)
add_library(libdocopt STATIC IMPORTED)
set_target_properties(libdocopt PROPERTIES IMPORTED_LOCATION ${DOCOPT_LIBRARIES})
add_dependencies(libdocopt docopt)
include_directories(${PROJECT_SOURCE_DIR})
include_directories(${DOCOPT_INCLUDE_DIRS})
file(GLOB projector_src
  "*.h"
  "*.cpp"
  )
add_executable(my_project ${my_project_src})
target_link_libraries(projector libdocopt)

显然，您不需要使用cmake，而是需要将docopt.cpp的源代码与您自己的代码一起放入，否则您需要告诉链接器在哪里查找它。cmake确实为您处理了这一点，但这是另一件需要担心的事情。

修改了Jeremiah Peschka的答案，使其独立于任何其他来源。


项目结构:

├── CMakeLists.txt
├── build
└── main.cpp


CMakeLists.txt 

cmake_minimum_required (VERSION 3.5)
project(my_project)
include(ExternalProject)
set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11" )
set(DOCOPT_ROOT ${PROJECT_SOURCE_DIR}/external/docopt)
set(DOCOPT_INCLUDE_DIRS ${DOCOPT_ROOT}/include/docopt)
set(DOCOPT_LIBRARIES ${DOCOPT_ROOT}/lib/libdocopt.a)
set(docopt_INSTALL_DIR "${DOCOPT_ROOT}")
set(docopt_CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${docopt_INSTALL_DIR})
ExternalProject_Add(docopt
  PREFIX ${DOCOPT_ROOT}
  GIT_REPOSITORY https://github.com/docopt/docopt.cpp.git
  BINARY_DIR ${DOCOPT_ROOT}
  INSTALL_DIR ${DOCOPT_ROOT}
  CMAKE_ARGS ${docopt_CMAKE_ARGS}
  LOG_DOWNLOAD ON
  LOG_CONFIGURE ON
  LOG_BUILD ON
  LOG_INSTALL ON
)
add_library(libdocopt STATIC IMPORTED)
set_target_properties(libdocopt PROPERTIES IMPORTED_LOCATION ${DOCOPT_LIBRARIES})
add_dependencies(libdocopt docopt)
include_directories(${PROJECT_SOURCE_DIR})
include_directories(${DOCOPT_INCLUDE_DIRS})
file(GLOB src
  "*.h"
  "*.cpp"
  )
add_executable(my_project ${src})
target_link_libraries(my_project libdocopt)
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