View source for KDevelop5/Manual/Getting started: A small CMake tutorial

== Getting Started with CMake ==

{{Construction}}

In this chapter, you will learn how to build your CMake based project and how to add files.

If you want do get a more in-depth tutorial on CMake, see [[KDevelop5/Manual/Appendix B: CMake for bigger projects|Appendix B: CMake for bigger projects]].

== Adding a file ==
[[image:kdevelop4_target_addfile.png|thumb|Create a File in a Target]]
Right-click on the project's main target and select <menuchoice>Create File</menuchoice>. You will be asked for a filename &ndash; enter <code>helloworld.cpp</code> here and click on "OK".

The dialog that pops up now shows the changes that will be made to <code>CMakeLists.txt</code>. For now, click on "OK".

The newly created file is now opened in the editor. Enter the following code and save the file:
<div class="clearfix"></div>
{{Input|#include <iostream>

void heyWorld() {
    std::cout << "Hello, world!";
} }}

== First compilation ==
There are several ways to compile your program.
; Target context menu
: Right-click on the target you want to build and click on <menuchoice>Build</menuchoice>.
; Projects Toolview button
: Click on the small button with the gear on it &ndash; it has the same functionality as the menu entry in the target context menu.
; Click on <menuchoice>Project -> Build Selection</menuchoice> or press <keycap>F8</keycap>.
: This is still the same functionality as described above.
; Click on <menuchoice>Project -> Build all Projects</menuchoice>.
: This does what you expect &ndash; it builds all your projects.

Now simply press <keycap>F8</keycap>.

On the first pass, '''KDevelop''' calls '''CMake''' and prints its output to the ''Build Toolview'' which pops up at the bottom:
{{Output|1=/home/sto/projects/kdevbook/build> /usr/bin/cmake -DCMAKE_BUILD_TYPE=Debug /home/sto/projects/kdevbook/
-- The C compiler identification is GNU
-- The CXX compiler identification is GNU
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - 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
-- Configuring done
-- Generating done
-- Build files have been written to: /home/sto/projects/kdevbook/build }}

After this step, the Makefiles have been generated, and '''KDevelop''' calls <code>make</code>:
{{Output|1=/home/sto/projects/kdevbook/build> make
Scanning dependencies of target kdevbook
[ 50%] Building CXX object CMakeFiles/kdevbook.dir/helloworld.cpp.o
[100%] Building CXX object CMakeFiles/kdevbook.dir/main.cpp.o
Linking CXX executable kdevbook
[100%] Built target kdevbook
*** Finished ***}}

Congratulations, you built your first application using KDevelop!

== More about targets ==
Now add the header file <code>helloworld.h</code> with the following contents to your project:
{{Input|1=void heyWorld();}}

And replace the <code>#include</code> directive with the following line at the top of <code>main.cpp</code>:
{{Input|1=#include "helloworld.h"}}

Finally, replace the line containing <code>std::cout << ...</code> with a call to <code>heyWorld();</code>. Now build your project again.

Let's take a look at <code>CMakeLists.txt</code> &ndash; open it by double-clicking on the file in the Projects Toolview. The first line in it defines the project's name. You may define the languages used by the project here &ndash; if not defined, they default to C and C++. Take a look at [http://www.cmake.org/cmake/help/cmake-2-8-docs.html#command:project the official documentation for the <code>project</code> command].

Now, let's take a look at the <code>add_executable</code> command: The first argument defines the name of the resulting executable, further arguments define the source files the executable is built from. Again, you may take a look at [http://www.cmake.org/cmake/help/cmake-2-8-docs.html#command:add_executable the official documentation for the <code>add_executable</code> command].

Let's create a separate target for our <code>helloworld.cpp</code> file by defining it as a static library and linking it to our executable. Replace the contents of the <code>CMakeLists.txt</code> with the following text:
{{Input|1=project(kdevbook)

add_library(kdevbook_lib STATIC helloworld.cpp)
add_executable(kdevbook main.cpp)

target_link_libraries(kdevbook kdevbook_lib)}}

So, what have we done? With <code>add_library</code>, we defined a static library which is built from <code>helloworld.cpp</code>. The library may be build from multiple source files, you just have to list them after the <code>STATIC</code> keyword. And with <code>target_link_libraries</code> we tell '''CMake''' to link our kdevbook target against kdevbook_lib &ndash; as the command name suggests, you can link multiple libraries to one target, again by simply listing the targets.

See the official documentation for [http://www.cmake.org/cmake/help/cmake-2-8-docs.html#command:add_library <code>add_library</code>] and [http://www.cmake.org/cmake/help/cmake-2-8-docs.html#command:target_link_libraries <code>target_link_libraries</code>].

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