Undefined reference to function CMake

47,678

Solution 1

Make sure that your test CMakeLists.txt links to the created library.

project(test)
cmake_minimum_required(VERSION 2.8)
set(SOURCE_FILES main.cpp)
include_directories( test2 )
#here
link_directories(test2)
add_subdirectory(test2)
add_executable( ${PROJECT_NAME} ${SOURCE_FILES} )
#and here
target_link_libraries( ${PROJECT_NAME} test2 )

Solution 2

Function add_subdirectory($dir) does not automatically add $dir to include directories and link directories. To use library test2 you should do it manually in CMakeLists.txt of test directory:

include_directories(test2/)
link_directories(test2/)

Then, link your executable with test2 library to get functions definitions. Add to CMakeLists.txt of test directory:

target_link_libraries(tests test2)

47,678

Exagon

Updated on April 21, 2020

Comments

Exagon about 3 years
I am trying to learn CMake, but I get a undefined reference to ... linker error I have a directory with a subdirectory. each of them has its own CMakeLists.txt
```
test
|----main.cpp
|----CMakeLists.txt
|----test2
     |----foo.hpp
     |----foo.cpp
     |----CMakeLists.txt
```
the CMakeLists.txt for test is:
```
cmake_minimum_required(VERSION 3.5)
project(tests)
add_subdirectory(test2)
set(SOURCE_FILES main.cpp)
add_executable(tests ${SOURCE_FILES})
```
the CMakeLists.txt for test2 is:
```
set(test2_files
        foo.cpp
        foo.hpp
        )
add_library(test2 ${test2_files})
```
foo.cpp implements a function which is defined in foo.hpp for this function I am getting the undefined reference error. What am I doing wrong? How can I get rid of this linker error

EDIT: My CMakeLists.txt now looks like this, but I still get the linker error:
```
project(tests)
cmake_minimum_required(VERSION 2.8)
set(SOURCE_FILES main.cpp)
include_directories(test2)
link_directories(test2)
add_subdirectory(test)
add_executable( ${PROJECT_NAME} ${SOURCE_FILES} )
target_link_libraries(${PROJECT_NAME} test2)
```
I also tried it with the absolute path instead of test2

EDIT: solved it it was only a typo in the CMakeLists.txt of test2.
Exagon almost 7 years

If I am using this I am getting this error: /usr/bin/ld: cannot find -ltest2
davepmiller almost 7 years

Added a line, give the top level a local for link directories.
davepmiller almost 7 years

Do you want it to be *.a or *.so? This implemenation generates a *.a file in the build directory.
Exagon almost 7 years

i tried it with link_directories(test2) also with absolute paths but it keep saying "udefined reference to..."
davepmiller almost 7 years

@Exagon. Did you get it working? Sorry, I've been away from computer for a couple days.