CMake not finding proper header/include files in include_directories

Question

Once again I am getting a "undefined symbols for architecture x86_64" error when I try to compile. I've tried more than I can actually document in this post (because I've forgotten all that I have tried). It is a really simple set-up and should compile very easily with CMake...

When I run a make on this it works just fine. But I want to convert it to CMake for interoperability. As you can see I have thrown my "${HEADERS}" variable in a few places, I've tried quite a few placements of it but I keep getting my error. Depending on where I put that ${HEADER} it can also technically generate an error of "error: cannot specify -o when generating multiple output files" (That applies if it only sits in the target_link_library declaration).

I have 2 folders:

Root
    Headers (contains all .h files)
    Source (contains all .cc/.cpp/.c files) (and also a CMakeLists.txt)
CMakeLists.txt

My root CMakeLists.txt contains the following:

cmake_minimum_required(VERSION 2.8.4)
project(Framework)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
add_compile_options("-v")

add_subdirectory(Source)

#Variables for making my life easier and adding the headers
set(H Headers)
include_directories(${H})
set(S Source)
file(GLOB HEADERS
#Add any file in the headers dir
"${H}/*"
)

# Create a variable to use for main.cc
set(MAIN ${S}/main.cc ${HEADERS})

# Add the main.cc file and headers
add_executable(Framework ${MAIN} ${HEADERS})

# Add the .cc/.cpp files
target_link_libraries(Framework ${SOURCE_FILES})

My CMakeLists.txt in my source directory contains the following:

file(GLOB SOURCES
"*.cc"
"*.cpp"
)

add_library(SOURCE_FILES ${SOURCES})

I do not have one in the headers as per, what I believe, the documentation states we don't need.

Thanks for the help. I've looked at:

• cmake including h files from other directories
• http://www.cmake.org/cmake/help/v2.8.0/cmake.html (both for version 2.x and 3.x)
• CMake Adding Headers to Projectfile -- had a potential for a solution but ended up saying "I don't know" :(
• and many other various mail lists and other sites

Answer 1

The main problem here is that you're referring to the SOURCE_FILES target as if it was a variable. Remove the dollar sign and curly braces.

target_link_libraries(Framework SOURCE_FILES)

It also seems kind of weird that you set include_directories after calling add_subdirectory, I'd be surprised if that worked.

Overall I think you're making things more complicated than they need to be. The following should be all that's necessary.

Top level CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
project(Framework CXX)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wextra -pedantic")

include_directories(
  ${PROJECT_SOURCE_DIR}/Headers
)

add_subdirectory(Source)

Source/CMakeLists.txt

# Do not use file globing because then CMake is not able to tell whether a file
# has been deleted or added when rebuilding the project.
set(HELLO_LIB_SRC
  hello.cc
)
add_library(hello ${HELLO_LIB_SRC})

set(MAIN_SRC
  main.cc
)
add_executable(hello_bin ${MAIN_SRC})
target_link_libraries(hello_bin hello)

Headers/hello.h

#pragma once

#include <string>

namespace nope
{
  std::string hello_there();
}

Source/hello.cc

#include <hello.h>

namespace nope
{
  std::string hello_there()
  {
    return "Well hello there!";
  }
}

Source/main.cc

#include <hello.h>
#include <iostream>

int main()
{
  std::cout << nope::hello_there() << std::endl;
  return 0;
}

Do not worry about the placement of files in the build folder. That's for the install step to figure out.

$ mkdir build && cd build
$ cmake -DCMAKE_BUILD_TYPE=Debug ..
$ make