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software:linux:yocto:getting_started_cpp [2020-03-25 14:44] – angelegt mlammerichsoftware:linux:yocto:getting_started_cpp [2024-04-23 13:08] (aktuell) – Moritz Lammerich
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-======= Getting started with Yocto and C/C++ =======+======= Getting Started with Yocto and C/C++ =======
  
-This guide will go through setting up a build environment and building an x86_64 image, and adding a small "hello world" application to it. First the application will be compiled using the [[ .:sdk | SDK ]], then it will be added to the image directly by creating a [[ .:recipes | recipe ]].+This guide will go through setting up a build environment and building an x86_64 image, and adding a small "hello world" application to it. This page is a summary of the information from [[software:linux:yocto:setup|Setup and Building]], [[software:linux:yocto:recipes|Recipes]] and [[software:linux:yocto:devtool|devtool]].
  
-===== Setting up the build environment =====+===== Setting up the Build Environment =====
  
 Create a directory in a suitable place to store everything related to this build. Create a directory in a suitable place to store everything related to this build.
 This guide will assume everything is in a directory called ''yocto'' in your the home of the user ''ubuntu'': ''/home/ubuntu/yocto''. This folder can by anywhere on the system though. This guide will assume everything is in a directory called ''yocto'' in your the home of the user ''ubuntu'': ''/home/ubuntu/yocto''. This folder can by anywhere on the system though.
  
-Next, clone ''poky'', [[..: | yocto's ]] reference distribution. At the time of writing ''yocto-3.0.2'' is the newest release, feel free to substitute it for a newer/different version.+Next, clone ''poky'', yocto's reference distribution. At the time of writing ''yocto-3.0.2'' is the newest release, feel free to substitute it for a newer/different version.
 <code> <code>
-git clone -b yocto-3.0.2 git://git.yoctoproject.org/poky+git clone -b kirkstone git://git.yoctoproject.org/poky
 </code> </code>
  
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 </code> </code>
  
-Now we can initialize [[..: | yocto ]] using:+Now we can initialize yocto using:
 <code> <code>
 . poky/oe-init-build-env build/ . poky/oe-init-build-env build/
 </code> </code>
-This will populate the build directory with all necessary files and give you access to ''bitbake'', the build system used by [[..: | yocto ]].+This will populate the build directory with all necessary files and give you access to ''bitbake'', the build system used by yocto.
  
-==== Setting the machine ====+==== Setting the Machine ====
  
-Setting the machine tells bitbake what hardware to build for. This build will be a generic x86_64 image, so we can set the machine to ''genericx86-64''.+Setting the machine tells bitbake what hardware to build for. This build will be a 64bit qemu image, so we can set the machine to ''qemu86-64''. This means we can run this image in Qemu.
  
 Open ''local.conf'' Open ''local.conf''
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 </code> </code>
  
-and add this line to set the machhine:+and add this line to set the machine:
 <code> <code>
-MACHINE = "genericx86-64"+MACHINE = "qemux86-64"
 </code> </code>
  
 The build environment is now set up. The build environment is now set up.
  
-===== Building an image =====+===== Building an Image =====
  
 You can now build an image. This command will build a minimal image provided by ''poky'': You can now build an image. This command will build a minimal image provided by ''poky'':
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 bitbake core-image-minimal bitbake core-image-minimal
 </code> </code>
 +
 +Once the image is built, it can be run in qemu using
 +
 +<code>
 +runqemu qemux86-64 nographic
 +</code>
 +
 +''runqemu'' is a script that comes with bitbake, ''qemux86-64'' specifies the machine, and ''nographic'' tells qemu to run in the terminal rather than its own window. This is useful when building on a system with no graphical environment such as a container or when building in the cloud.
 +
 +The default login is ''root'' with no password. You can use ''poweroff'' to shut down the virtual machine and exit qemu.
 +
 +===== Creating a Hello World C++ Application =====
 +
 +This section will show you how to create a hello world application in C++ with Cmake.
 +
 +First, create a directory in your yocto folder. This will contain the application itself.
 +The location is arbitrary, and was chosen merely for convenience. It could be anywhere.
 +Assuming you are still in the ''build'' directory:
 +
 +<code>
 +mkdir ../helloworld
 +</code>
 +
 +Next, create a ''main.cpp'' in the new directory
 +
 +<code>
 +cd ../helloworld
 +nano helloworld.cpp
 +</code>
 +
 +with the following content:
 +
 +<code>
 +#include<iostream>
 +
 +int main()
 +{
 +        std::cout << "Hello World!\n";
 +        return 0;
 +}
 +</code>
 +
 +Now create a ''CMakeLists.txt'' for cmake:
 +
 +<code>
 +nano CMakeLists.txt
 +</code>
 +
 +CMakeLists.txt
 +<code>
 +cmake_minimum_required(VERSION 3.5)
 +
 +project(yocto-test LANGUAGES CXX)
 +
 +add_executable(hello helloworld.cpp)
 +
 +install(TARGETS hello DESTINATION bin)
 +
 +</code>
 +
 +==== Optional: Verifying that the Application Works ====
 +
 +This is an optional step to verify the application itself is built correctly before adding it to the image.
 +Create a ''build'' directory inside the application folder for cmake to store its data in.
 +Then execute ''cmake'' inside that folder to create the build configuration and build the 
 +application by running ''make''.
 +Now there should be a ''hello'' executable that prints "hello world" when executed.
 +After confirming it works, change back to ''yocto/build'' before continuing with the next step.
 +
 +<code>
 +mkdir build
 +cd build
 +cmake ..
 +make
 +./hello
 +cd ../../build
 +</code>
 +
 +===== Creating a Recipe for the application =====
 +
 +We use [[software:linux:yocto:devtool|devtool]] to create a new [[ .:recipes | Recipe ]] for our ''hello'' application.
 +<code>
 +devtool add ../helloworld/
 +</code>
 +
 +This should finish with a message similar to this one:
 +<code>
 +INFO: Recipe /home/ubuntu/yocto/build/workspace/recipes/helloworld/helloworld.bb has been automatically created; further editing may be required to make it fully functional
 +</code>
 +
 +This means devtool ran successfully and created a recipe at the specified location. 
 +
 +To test whether this recipe works, build it by running bitbake:
 +
 +<code>
 +bitbake helloworld
 +</code>
 +
 +This should run without errors and print something like this when it's finished:
 +
 +<code>
 +NOTE: Tasks Summary: Attempted 506 tasks of which 497 didn't need to be rerun and all succeeded.
 +</code>
 +
 +This means the package provided by the recipe was built successfully.
 +
 +===== Adding the Recipe to the Image =====
 +
 +Now that we have a recipe, we need to add it to the image to test it out.
 +Adding packages to recipes is done in ''conf/local.conf'' by appending them to ''CORE_IMAGE_EXTRA_INSTALL'':
 +
 +Edit ''local.conf''
 +<code>
 +nano conf/local.conf
 +</code>
 +
 +and add the following:
 +<code>
 +CORE_IMAGE_EXTRA_INSTALL += "helloworld"
 +</code>
 +
 +Rebuild the image
 +<code>
 +bitbake core-image-minimal
 +</code>
 +
 +And run qemu
 +
 +<code>
 +runqemu qemux86-64 nographic
 +</code>
 +
 +Log in as ''root'' and you can now run our ''hello'' application:
 +<code>
 +root@qemux86-64:~# hello
 +Hello World!
 +</code>
 +
 +Congratulations! You have now developed your own C++ application and added it to a yocto image.

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software/linux/yocto/getting_started_cpp.1585143884.txt.gz · Zuletzt geändert: 2020-03-25 14:44 von mlammerich