GTest linking error: undefined reference to 'foo::function'

Question

我想使用 GTest 并让示例运行。现在我想测试我自己的代码，但是我遇到了一个 linking 问题。

我在 Whosebug 上搜索过，发现了一个类似的问题，但答案并没有帮助我解决问题。

我的文件是：

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)

SET(CMAKE_CXX_FLAGS "-std=gnu++11")

# Locate GTest
find_package(GTest REQUIRED)
include_directories(${GTEST_INCLUDE_DIRS})
file(GLOB files
    Datahandler.h 
    Datahandler.cpp 
    )

# Link runTests with what we want to test and the GTest and pthread library
add_executable(runTests tests.cpp ${files} )
target_link_libraries(runTests ${GTEST_LIBRARIES} pthread)

tests.cpp

#include "DataHandler.h"
#include <gtest/gtest.h>

TEST(checkFilled, All){
    DataHandler handler("loc", "prot", 1);
    handler.filledElement[1] = 1;
    ASSERT_EQ(1, handler.checkFilled(1));
    ASSERT_EQ(0, handler.checkFilled(2));
    ASSERT_EQ(1, handler.checkFilled(8));
    ASSERT_EQ(0, handler.checkFilled(9));
}

int main(int argc, char **argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

我得到的错误是：

CMakeFiles/runTests.dir/tests.cpp.o: In function `checkFilled_All_Test::TestBody()':
tests.cpp:(.text+0x121): undefined reference to `DataHandler::DataHandler(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, unsigned char)'
tests.cpp:(.text+0x172): undefined reference to `DataHandler::checkFilled(unsigned char)'
tests.cpp:(.text+0x271): undefined reference to `DataHandler::checkFilled(unsigned char)'
tests.cpp:(.text+0x382): undefined reference to `DataHandler::checkFilled(unsigned char)'
tests.cpp:(.text+0x48d): undefined reference to `DataHandler::checkFilled(unsigned char)'
collect2: error: ld returned 1 exit status
CMakeFiles/runTests.dir/build.make:95: recipe for target 'runTests' failed
make[2]: *** [runTests] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/runTests.dir/all' failed
make[1]: *** [CMakeFiles/runTests.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

我几乎可以肯定它与 include 或 link 问题有关，但我找不到正确的语法。

Answer 1

你的CMake项目有几点：

SET(CMAKE_CXX_FLAGS "-std=gnu++11")

使用 CMAKE_CXX_FLAGS 时，最好不要删除以前的值：

SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")

默认情况下，该值为空，因此不应在此处更改任何内容。无论如何，要要求 C++11，您可以考虑 CMAKE_CXX_STANDARD:

SET(CMAKE_CXX_STANDARD 11)
SET(CMAKE_CXX_STANDARD_REQUIRED ON)

下一个：

file(GLOB files
    Datahandler.h 
    Datahandler.cpp 
    )

如果您使用 GLOB，您应该传递文件模式，而不是文件路径。无论如何，从 doc:

We do not recommend using GLOB to collect a list of source files from your source tree. If no CMakeLists.txt file changes when a source is added or removed then the generated build system cannot know when to ask CMake to regenerate.

改为考虑 set：

set(files
    Datahandler.h 
    Datahandler.cpp 
    )

下一个：

include_directories(${GTEST_INCLUDE_DIRS})

#...

target_link_libraries(runTests ${GTEST_LIBRARIES} pthread)

你可以考虑 imported targets:

而不是老式的 ${GTEST_LIBRARIES}

target_link_libraries(runTests GTest::Main)

GTest::Main 将通过导入的目标处理包含目录，因此您无需调用 include_directories。此外，它会添加对线程库的依赖，所以我很确定你可以删除 pthread （待测试）。最后，GTest::Main 包含了 main 函数的基本实现，它与您所做的完全相同，因此您可以删除自己的函数。

请注意，您需要升级 CMake 的最低要求版本才能使导入的目标完全可用：

cmake_minimum_required(VERSION 2.8.11)

因此您在 2016 年的 CMake 项目应该如下所示：

cmake_minimum_required(VERSION 2.8.11)

SET(CMAKE_CXX_STANDARD 11)
SET(CMAKE_CXX_STANDARD_REQUIRED ON)

set(files
    Datahandler.h 
    Datahandler.cpp 
    )

# Locate GTest
find_package(GTest REQUIRED)

# Link runTests with what we want to test and the GTest library
add_executable(runTests tests.cpp ${files})

target_link_libraries(runTests GTest::Main)

和test.cpp：

#include "DataHandler.h"
#include <gtest/gtest.h>

TEST(checkFilled, All){
    DataHandler handler("loc", "prot", 1);
    handler.filledElement[1] = 1;
    ASSERT_EQ(1, handler.checkFilled(1));
    ASSERT_EQ(0, handler.checkFilled(2));
    ASSERT_EQ(1, handler.checkFilled(8));
    ASSERT_EQ(0, handler.checkFilled(9));
}

GTest linking error: undefined reference to 'foo::function'

GTest linking error: undefined reference to 'foo::function'

c++

c++11

cmake

googletest

undefined-reference