cmake-examples

= Imported Targets
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# Introduction

As previously mentioned in the link:../H-third-party-library[third party library], newer
versions of CMake allow you to link third party libraries using link:https://cmake.org/cmake/help/v3.6/prop_tgt/IMPORTED.html#prop_tgt:IMPORTED[imported] +ALIAS+ targets.

The files in this tutorial are below:

```
$ tree
.
├── CMakeLists.txt
├── main.cpp
```

  * link:CMakeLists.txt[] - Contains the CMake commands you wish to run
  * link:main.cpp[] - The source file with main

# Requirements

This example requires the following:

  * CMake v3.5+
  * The boost libraries to be installed in a default system location. 

# Concepts

## Imported Target

Imported targets are read-only targets that are exported by FindXXX modules. 

To include boost filesystem you can do the following:

[source,cmake]
----
  target_link_libraries( imported_targets
      PRIVATE
          Boost::filesystem
  )
----

This will automtaically link the Boost::filesystem and Boost::system libraries while also including the
Boost include directories.

# Building the Example

[source,bash]
----
$ mkdir build

$ cd build/

$ cmake ..
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- 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
-- Boost version: 1.58.0
-- Found the following Boost libraries:
--   filesystem
--   system
boost found
-- Configuring done
-- Generating done
-- Build files have been written to: /data/code/01-basic/K-imported-targets/build

$ make
Scanning dependencies of target imported_targets
[ 50%] Building CXX object CMakeFiles/imported_targets.dir/main.cpp.o
[100%] Linking CXX executable imported_targets
[100%] Built target imported_targets


$ ./imported_targets
Hello Third Party Include!
Path is not relative


----