Finding GLib with CMake: target_include_directories called with invalid arguments

I have this following (minimal) CMakeLists.txt supposed to find GLib via pkg-config and add the libs to the foo target:

cmake_minimum_required(VERSION 2.10 FATAL_ERROR)
project(foo)
find_package(PkgConfig REQUIRED)
pkg_check_modules(GLib REQUIRED glib-2.0)
add_executable(foo foo.cpp)
message(WARNING "libs:" ${GLIB_LIBRARIES})
message(WARNING "includes:" ${GLIB_INCLUDE_DIRS})
target_link_libraries(foo PUBLIC ${GLIB_LIBRARIES})
target_include_directories(foo PUBLIC ${GLIB_INCLUDE_DIRS})

No matter what I try, I get (note the Found glib-2.0 part):

-- The C compiler identification is GNU 7.3.0
-- The CXX compiler identification is GNU 7.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.29.1") 
-- Checking for module 'glib-2.0'
--   Found glib-2.0, version 2.56.1
CMake Warning at CMakeLists.txt:6 (message):
  libs:


CMake Warning at CMakeLists.txt:7 (message):
  includes:


CMake Error at CMakeLists.txt:9 (target_include_directories):
  target_include_directories called with invalid arguments


-- Configuring incomplete, errors occurred!
See also "/tmp/aaa/CMakeFiles/CMakeOutput.log".

and I cannot see, reading the CMake reference what arguments are invalid (note: this question is different from cmake target_include_directories called with invalid arguments). I also looked at CMake's FindPkgConfig documentation which gives glib as an example and I am not able to reproduce it (${GLIB_VERSION}). I tried GLIB_ and GLIB2_ prefixes and all I get is empty strings.

The messages show the variables are empty, though pkg-config reports values correctly:

$ pkg-config glib-2.0 --cflags --libs
-I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -lglib-2.0

The CMake version I have is 2.10.

Can someone shed light on the issue?

Solution

I think your problem is the casing of GLIB_INCLUDE_DIRS and GLIB_LIBRARIES. They should be GLib_INCLUDE_DIRS and GLib_LIBRARIES since you specified "GLib" as the first argument of pkg_check_modules. I'm guessing that the target_include_directories() doesn't like not getting any arguments after the PUBLIC (although it works for me in cmake 3.5).