cmake - undefined reference to

问题

I am new to cmake and know this question has been asked before, but still cannot find what I am doing wrong. I have an external library with folders /include and lib. The /include folder contains all the headers (.h) and the /lib folder contains all the source (.c) files.

In my project I have this CMakeList.txt file:

cmake_minimum_required(VERSION 3.7)
project(FirstAttempt)

set(CMAKE_CXX_STANDARD 11)

set (EXTRA_LIBS "D:\\libtrading")

include_directories(${EXTRA_LIBS}/include)
link_directories(${EXTRA_LIBS}/include)

set(SOURCE_FILES main.cpp)
add_executable(FirstAttempt ${SOURCE_FILES})

target_link_libraries (FirstAttempt  ${EXTRA_LIBS}/lib)

I know that I have to use target_link_libraries to link the source files of the library to my project, but certainly something is missing, but what? I am still receiving the error undefined reference to xxxxxx.

The library I am trying to include in my project is https://github.com/libtrading/libtrading.

回答1:

Well, I'll try.

First, seems that you are calling link_directories() on the folder which contains header files, while it should be used in order to specify the path where to search libraries for.

Second, target_link_libraries() takes the absolute path of the shared/static library file as the second argument, while you are passing the directory path (well, it seems so).

target_link_libraries() doesn't link to the "source files of the library", - it links to the compiled shared/static library blob.

And, I would also recommend you to save the name of the executable to the variable so that you wouldn't be able to mistype the target name, like so:

set(TARGET FirstAttempt)
add_executable(${TARGET})

回答2:

As you know, we need all source files to compile. So we need to point out Cmake know where/what are source files.

I think you should add all sources files like this

file(GLOB SOURCES_FILES "lib/*.c" main.cpp)

to add all .c files.

Or, you can add all lib/*.c files separately

file(SOURCES_FILES_LIBS "lib/*.c")
set(SOURCES_FILES main.cpp)
add_executable(FirstAttempt ${SOURCES_FILES_LIBS} ${SOURCES_FILES})

来源：https://stackoverflow.com/questions/45626584/cmake-undefined-reference-to

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c++

cmake