How to use libxml2 with CMake? - cmake

Question

I am using CLion editor (with CMake) for my C project,
I've never used an external library though,
my question is how do I link an external lib (for ex. libxml2) to my project?
I've seen some questions similar to this but none worked for me.
My project is compiled on Windows, and I have libxml .dll, include, and .lib files(binaries for Windows).
Edit: My CMakeLists.txt file after the answer suggested:
cmake_minimum_required(VERSION 3.2)
project(time_table)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
set(SOURCE_FILES
course.c
course.h
day.h
defines.h
find_tables.c
find_tables.h
item.h
parse_info.c
parse_info.h
table.c
table.h
time_table.c grades.c grades.h)
link_libraries(C:/Users/Gal/Desktop/time_table/libxml2-2.7.8.win32/lib)
add_executable(time_table ${SOURCE_FILES})
target_link_libraries(time_table libxml2)
and this is what I get:
"C:\Program Files (x86)\JetBrains\CLion 1.1.1\bin\cmake\bin\cmake.exe" --build C:\Users\Gal\.clion11\system\cmake\generated\2eda76ff\2eda76ff\Debug --target time_table -- -j 8
[ 14%] Linking C executable time_table.exe
c:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe: cannot find -llibxml2
collect2.exe: error: ld returned 1 exit status
mingw32-make.exe[3]: *** [time_table.exe] Error 1
CMakeFiles\time_table.dir\build.make:225: recipe for target 'time_table.exe' failed
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/time_table.dir/all' failed
mingw32-make.exe[2]: *** [CMakeFiles/time_table.dir/all] Error 2
CMakeFiles\Makefile2:78: recipe for target 'CMakeFiles/time_table.dir/rule' failed
mingw32-make.exe[1]: *** [CMakeFiles/time_table.dir/rule] Error 2
What is wrong?

Answer 1

There is a key work for libraries installed on your machine. <lib_name>_INCLUDE_DIR and <lib_name>_LIBRARIES once you have done find_package. This works for me.
find_package(LibXml2 REQUIRED)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/<my_stuff> ${LIBXML2_INCLUDE_DIR})
add_executable(<my_exe> <my_source_files>)
target_link_libraries(<my_exe> ${LIBXML2_LIBRARIES})
---- Just a note for your curiosity ----
If you ever needed to build (1) a (static) library of your calculations, maybe reusable, and (2) an executable that uses that library and LIBXML2, do this.
find_package(LibXml2 REQUIRED)
# add a calculation library: file "lib<mycalc>.a"
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/<your header files folder> ${LIBXML2_INCLUDE_DIR})
add_library(<mycalc> STATIC ${CMAKE_CURRENT_SOURCE_DIR}/<your src files folder>)
target_link_libraries(<mycalc> ${LIBXML2_LIBRARIES})
# add the executable: file <my_exe>
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/<your header files folder> ${LIBXML2_INCLUDE_DIR})
add_executable(<my_exe> <your exe src files>)
target_link_libraries(<my_exe> <mycalc> ${LIBXML2_LIBRARIES})

Answer 2

Assume that full path to the library(.lib) can be expressed as
<library_dir>/<library_name>.lib
For compile executable, which uses this library, you need:
CMakeLists.txt:
link_libraries(<library_dir>)
add_excutable(<my_exe> ..)
target_link_libraries(<my_exe> <library_name>)
For use(run) compiled executable, you need to have <library_name>.dll either under one of the directory, listed in the PATH environment variable, or within same directory with executable.

Answer 3

there are 32bit and 64bit version of libxml2, to be found here.
you can put them below the PATH - or the C:\Windows directory.

Answer 4

With moderns CMake (version 3.2 or newer), it got much easier:
Search for the library. CMake has an according find module, thus it boils down to
find_package(LibXml2 REQUIRED)
Then you can link the library it to your target foo
target_link_libraries(foo PUBLIC LibXml2::LibXml2)
That's it folks! No fiddling around with headers and libraries, all done automatically.
If you have not installed the library, you might want to set LibXml2_DIR to the location where LibXml2 is located, i.e., by passing -DLibXml2_DIR=C:\software\libxml2 to your CMake call. That will help CMake finding LibXml2.