Build a demo project

Prequisites

You should have Bob somewhere in your $PATH. As the first step clone the tutorial projects:

$ git clone https://github.com/BobBuildTool/bob-tutorials.git
$ cd bob-tutorials/sandbox

This tutorial will use the sandbox example that should work basically everywhere. The next steps are all executed in the same directory.

Build release

To see the packages that you can build type:

$ bob ls -r
/
└── vexpress
    ├── initramfs
    │   ├── busybox
    │   └── toolchain::arm-linux-gnueabihf-rootfs
    ├── linux-image
    ├── sandbox::debian-x86_64
    └── toolchain::arm-linux-gnueabihf-toolchain

As you can see there is a single top-level package called vexpress. This demo project builds a QEMU image for the ARM Versatile Express machine. To build the project simply do the following:

$ bob build vexpress

This will fetch the toolchains and sources and will build the image locally in the work directory. To speed up the build you can optionally add -j to build packages in parallel. See the bob build manpage for all available options. Grab a coffee and after some time the build should finish:

...
>> vexpress
   BUILD     work/vexpress/build/1/workspace
   PACKAGE   work/vexpress/dist/1/workspace
Build result is in work/vexpress/dist/1/workspace

Now you can run the example if you have QEMU installed:

$ ./work/vexpress/dist/1/workspace/run.sh

Some words about the directory layout. The general layout is work/<package>/{src,build,dist}/#/ where:

  • <package> is the name of the package. In case of namespaces that might be several subdirectories, e.g. toolchain::arm-linux-gnueabihf will be built in work/toolchain/arm-linux-gnueabihf/....

  • {src,build,dist} corresponds to the result of the step, e.g. src is where the checkout step is run.

  • # is a sequential number starting from 1 that is increased for every variant of the package. New variants can emerge as recipes are updated.

Under the directory of a package you can find the following files and directories:

  • workspace/: This is the directory where the step is executed and that holds the result.

  • {checkout,build,package}.sh: A wrapper script that executes this specific step. Running the script will execute this particular step again. If you call the script with shell as first argument a new shell is spawned with exactly the same environment as the step script would find.

  • script: The actual script that was computed from the recipe and the inherited classes. This is not directly executable because it expects the right environment and arguments.

  • log.txt: Logs of all runs.

Development build

When executing bob build you build the requested packages in release mode. This mode is intended for reproducible builds. The example already employs a sandbox so that no host tools or paths are used. Though this is great for binary reproducible builds it is inconvenient to debug and incrementally change parts of the project.

For this purpose you can build the project in development mode via bob dev. This mode basically does the same things but with some important differences:

  • Sandboxes are not used by default. The host should have the required development tools installed, for example make, gcc, perl and so on. You may still build inside a sandbox by adding the --sandbox option.

  • Different directory layout to group sources, build and results of all packages: dev/{src,build,dist}/<package>/#/.

  • Incremental builds.

  • Stable directory tree with incremental updates to the workspace.

In this mode it is possible to build packages, make some changes and rebuild. If your environment has the right tools installed you should get the same result as the release mode. But because sandboxes are not used it is still possible to debug the created binaries. So let’s build the kernel in development mode:

$ bob dev vexpress/linux-image
>> vexpress/toolchain::arm-linux-gnueabihf-toolchain
   CHECKOUT  dev/src/toolchain/arm-linux-gnueabihf/1/workspace
>> vexpress/linux-image
   CHECKOUT  dev/src/linux/1/workspace
>> vexpress/toolchain::arm-linux-gnueabihf-toolchain
   BUILD     dev/build/toolchain/arm-linux-gnueabihf-toolchain/1/workspace
   PACKAGE   dev/dist/toolchain/arm-linux-gnueabihf-toolchain/1/workspace
>> vexpress/linux-image
   BUILD     dev/build/linux-image/1/workspace
   PACKAGE   dev/dist/linux-image/1/workspace
Build result is in dev/dist/linux-image/1/workspace
Duration: 0:04:40.737003, 2 checkouts (0 overrides active), 2 packages built, 0 downloaded.

Notice that the development mode builds in a separate directory: dev. The numbering beneath the package name directory is kept stable. The numbers represent only the currently possible variants of the package from the recipes. If the checkoutSCM in the recipe is changed the old checkout will be moved aside instead of using a new directory like in the release mode.

Suppose we want to make a patch to the kernel. This is as simple as to go to dev/src/linux/1/workspace, edit some files and call Bob again to rebuild, e.g.:

$ vi dev/src/linux/1/workspace/init/main.c
$ bob dev vexpress/linux-image

Bob will detect that there are changes in the sources of the kernel and make an incremental build. For the sake of simplicity we might rebuild the top-level package to test the full build:

$ bob dev vexpress
$ ./dev/dist/vexpress/1/workspace/run.sh

Note

Touching (touch ...) source files will not have any effect. Bob detects changes purely by its content and not by looking on the file meta data.

Now that we have a kernel we might want to change the kernel configuration and rebuild the kernel with the new one. From the output you can see that the kernel was built in dev/build/linux-image/1/workspace. We might edit the .config there directly but using make menuconfig is much more convenient:

$ ./dev/build/linux-image/1/build.sh shell -E
$ make menuconfig

Now make and save your changes. Then rebuild the kernel:

...
  HOSTLD  scripts/kconfig/mconf
scripts/kconfig/mconf  Kconfig
configuration written to .config

*** End of the configuration.
*** Execute 'make' to start the build or try 'make help'.

$ make -j $(nproc) bzImage
$ exit

If you know how grab the kernel image directly out of the build tree and test it. Alternatively you can rebuild the top-level package.

$ bob dev vexpress
...
>> vexpress/linux-image
   BUILD     skipped (unchanged input for dev/build/linux-image/1/workspace)
   PACKAGE   dev/dist/linux-image/1/workspace
>> vexpress
   BUILD     dev/build/vexpress/1/workspace
   PACKAGE   dev/dist/vexpress/1/workspace
Build result is in dev/dist/vexpress/1/workspace
Duration: 0:00:01.643519, 0 checkouts (0 overrides active), 2 packages built, 0 downloaded.

and test the whole QEMU image. The choice is yours.

Warning

Making changes to the build step tree is only detected by Bob in development mode. These changes should be properly saved in the sources or the recipe before moving on. Otherwise you risk that your changes are wiped out if Bob determines that a clean build is needed (e.g. due to recipe changes).

Out of tree builds

The bob-dev and bob-build commands do not need to be executed in the project directory directly. It is also possible to initialize an external build directory with bob-init:

$ bob init . /path/to/build/directory
$ cd /path/to/build/directory
$ bob dev vexpress

Each build directory can have its own User configuration (default.yaml) that overrides the defaults of the project.

Query SCM status

After you have developed a great new feature you may want to know which sources you have touched to commit them to a SCM. Bob offers the bob status command to show a list of SCM which are unclean. SCMs are unclean in case they have modified files, unpushed commits, switched URLs or non matching tags or commit ids.

The output looks like the following line:

STATUS <status code> <scm path>

Status codes:

  • U : Unpushed commits (Git only)

  • u : unpushed commits on local branch (Git only)

  • M : Modified sources.

  • S : Switched. Could be different tag, commitId, branch or URL.

  • O : Overridden. This Scm is overridden (scmOverrides). Depends on --show-overrides.

Using IDEs with Bob

You may want to use an IDE with Bob. At the moment Qt Creator and Eclipse are supported. You can add more IDEs using Generators extension. To generate project files the basic call is:

$ bob project <genericArgs> <generator> <package> <specificArgs>

with genericArgs:

  • -n: Do not build. Usually bob project builds the given package first to be able to collect binaries and add them to the IDEs run/debug targets.

  • -D -c -e -E: These arguments will be passed to bob dev and will also be used when compiling from IDE.

with generator:

  • eclipseCdt: Generate project files for eclipse. Tested with eclipse MARS.

  • qt-creator: Generate project files for QtCreator. Tested with 4.0 and 4.1.

and package which is the name of a package to generate the project for. Usually all dependencies for this package will be visible in the IDE. The specificArgs arguments are used by the generator itself. They differ from generator to generator (see below).

QTCreator

Because we have already built the sandbox tutorial it is very fast to generate a Qt Creator project and open it:

$ bob project qt-creator vexpress
...
>> vexpress
   BUILD     skipped (unchanged input for dev/build/vexpress/1/workspace)
   PACKAGE   skipped (unchanged input for dev/dist/vexpress/1/workspace)
Build result is in dev/dist/vexpress/1/workspace
Duration: 0:00:00.847041, 0 checkouts (0 overrides active), 0 packages built, 0 downloaded.
>> vexpress
   PROJECT   vexpress (qt-creator)
$ qtcreator projects/vexpress/vexpress.creator

After loading the project Qt Creator will need quite some time to scan the sources of the Linux kernel. You could add an --exclude linux-image to hide this big package from Qt Creator if you do not intend to work on it from the IDE.

QtCreator specific Arguments:

  • --destination: destination directory for the project files. Default is <workingDir>/projects/package_stack.

  • --name: name of the project. Default is packageName.

  • -I: additional include directories. They will only be added for indexer and will not change the buildresult.

  • -f: additional files. Normally only c[pp] and h[pp] files will be added. You can add more files using a regex.

  • --kit: kit to use for this project. You may want to use a different sysroot for includes and built-in preprocessor settings from your compiler. To tell QtCreator which toolchain to use you need to specify a kit. There are at least two options to create a kit: using the GUI or the sdkTools.

The following example shows how to create a cross compiling project for the sandbox-tutorial and the included arm-toolchain:

$ sdktool addTC \
    --id "ProjectExplorer.ToolChain.Gcc:arm" \
    --name "ARM-Linux-Gnueabihf" \
    --path "<toolchain-dist>/gcc-linaro-arm-linux-gnueabihf-4.9-2014.09_linux/bin/arm-linux-gnueabihf-g++" \
    --abi arm-linux-generic-elf-32bit
$ sdktool addDebugger \
    --id "gdb:ARM32" \
    --name "ARM-gdb" \
    --binary <toolchain-dist>/gcc-linaro-arm-linux-gnueabihf-4.9-2014.09_linux/bin/arm-linux-gnueabihf-gdb
$ sdktool addKit \
    --id "ARM_Linux" \
    --name "ARM Linux Gnueabi" \
    --devicetype Desktop \
    --toolchain "ProjectExplorer.ToolChain.Gcc:arm" \
    --sysroot <toolchain-dist>/gcc-linaro-arm-linux-gnueabihf-4.9-2014.09_linux/arm-linux-gnueabihf/libc/ \
    --debuggerid "gdb:ARM32"
$ bob project qt-creator vexpress --kit ARM_LINUX

EclipseCdt

Eclipse specificArgs:

  • --destination: destination directory for the project files. Default is <workingDir>/projects/package_stack.

  • --exclude: eclipse indexer sometimes runs OutOfMemory on large sourcetrees. You can specify package names (or use a regular expression) to define packages excluded from build. This will stop indexer from indexing these packages.

  • --name: name of the project. Default is packageName.

  • -I: additional include directories. They will only be added for indexer and will not change the buildresult.

Visualizing dependencies

A dependency graph visualizes your package dependencies. Bob supports two different graph types: ‘dot’ and ‘d3’.

For the sandbox-tutorial the output of

$ bob graph vexpress -t dot
$ dot -Tpng -osandbox_graph.png graph/vexpress.dot

gives you the following image:

../_images/sandbox_graph.png

For more complex projects ‘dot’ graphs don’t scale well. Therefore you can create interactive graphs using the d3 javascript library:

Using bob graph with the basement-project, enable node dragging and highlighting the zlib packages:

$ bob graph sandbox -H zlib.* -o d3.dragNodes=True