|Title:||catkin_make_isolated for non-standard catkin packages|
|Author:||William Woodall, Dirk Thomas, Thibault Kruse|
This REP describes the new command catkin_make_isolated to be delivered with catkin . This command builds each item in a workspace in an isolated environment, providing debugging for workspaces consisting purely of catkin packages and enabling users to build workspaces containing both catkin and non-catkin packages.
The REP introduces a new tag to use in the exports section of the package.xml:
Catkin commands will use the value of this tag to determine how to treat a package. Currently only two values are defined, "catkin" and "cmake", but further build types may be added later (possible examples could be make, autotools, rosbuild, or custom). "catkin" is the default value for this property that will be assumed in the absence of the tag.
Having a package with a build_type other than "catkin" in a catkin workspace will prevent that workspace from being built normally, either by invoking catkin_make or by invoking cmake path/to/workspace on a workspace with a top-level CMakeList.txt. Instead, the user will have to invoke a new command catkin_make_isolated, which builds each package in the workspace individually, calling cmake, make, and possibly make install for each catkin package. This is opposed to how catkin workspaces are normally built, with one invocation of CMake which generates a single Make target for all packages in the workspace. This is necessary as non-standard catkin packages do not act compliantly within the configuration process (they do not generate catkin-compliant configuration files during configuration so that other packages could depend on them after configuration).
catkin_make_isolated by default uses a build and devel space named differently than the default catkin build, devel, and install spaces:
catkin_make_isolated uses the information from catkin package manifests in the workspace to construct a valid build order for the packages. Then for each package, a build and devel subfolder are created in the build and devel spaces. For each package, catkin_make_isolated then invokes cmake and make in an environment which includes all devel spaces of dependencies of a given package. Later invocations just invoke make.
catkin_make_isolated will not create a CMakeLists.txt in the source space, in contrast to catkin_make, as this is only needed for the non-isolated build process. Similarly, there is no option to invoke configuration and build of multiple packages in a workspace with single commands other than by invoking catkin_make_isolated, in contrast to catkin_make which is practically equivalent to invoking cmake and make manually.
Any other build system than catkin to be supported has to satisfy the following constraints:
Additionally, build systems should strive to support the following:
catkin_make_isolated has the same options as catkin_make where those can be applied. catkin_make_isolated also requires extra options:
--devel DEVEL, --devel-space DEVEL Sets the target parent devel space (default "devel_isolated") --merge Build each catkin package into a common devel space. --install-space INSTALL_SPACE Sets the target install space (default "install_isolated") --install Causes each catkin package to be installed.
With catkin_make those options are not provided as they are passed as CMAKE variables / targets instead. In the isolated build, that is not possible because the actual CMake variables have to be set differently for each package, hence these options only need to exist in catkin_make_isolated.
Options that are currently shared with catkin_make:
-j [JOBS], --jobs [JOBS] --force-cmake --no-color --pkg PKGNAME [PKGNAME ...] -q, --quiet --cmake-args [CMAKE_ARGS [CMAKE_ARGS ...]] --make-args [MAKE_ARGS [MAKE_ARGS ...]]
As catkin evolves, such helper options may change, this REP is not an attempt to capture all options for all time.
By default catkin_make_isolated will create a build folder for package foo at:
For packages with a plain cmake build type subfolders are created under that folder called devel and install in order to cleanly separate them.
catkin_make only creates one build space for all packages at:
By default catkin_make_isolated will create a devel folder for package foo at:
whereas catkin_make only creates one devel space for all packages at:
The devel space folder:
will contain setup.* files to use to create a runtime environment.
For both standard as well as non-standard packages, catkin_make_isolated generates environment files (env.sh, setup.*) in the packages devel space. The isolated build space of a package can be used to (re-)build the package using the make command, provided the prerequisite packages are in the CMAKE_PREFIX_PATH. The env.sh file in the isolated devel space of the package can be used to run CMake with a suitable environment.
A --merge option allows to use a single devel space for all packages, while the build spaces remain isolated.
Passing --install will invoke make install for normal catkin packages in each isolated build space, and in non-standard packages, the behavior will be defined by each alternative build system support.
The initial support for non-standard catkin packages using the plain CMake build system is implemented by invoking make in the isolated build space of a package. After that the CMake project is installed to the devel space to comply with the devel space concept.
Catkin defines a catkin package to be a folder containing a package.xml file satisfying the catkin syntax and a CMakeList.txt.
Catkin provides CMake macros and variables, in particular the catkin_package() macro, which performs necessary steps for a catkin package to be build successfully in the catkin build process. This relates to the configure process of a package also generating suitable configuration files for dependent packages, as well as placing suitable build artifacts in the so called devel space.
However it is technically feasible to create a catkin package that does not use the provided catkin CMake macros or variables. The CMakeLists.txt then defines a build process according to e.g. plain CMake rules. Such a project which is not compliant with catkin breaks the default catkin build process (mainly due to the lack of catkin-generated CMake configuration file, and due to the absence of valid devel space files).
Several libraries in the ROS ecosystem have a complex CMakeLists.txt setup, and some maintainers may be reluctant to maintain a catkin-compliant CMakeLists.txt.
This introduces the notion of a non-standard catkin package. Such a package has a package.xml file, but does not follow any convention about the CMakeLists.txt. This REP defines basic support for an alternative build process that can also include such non-standard catkin packages. This measure is a workaround and not currently intended for the majority of catkin users. Current caveats are very low speed, and a folder layout that is different from the layout generated by catkin_make. The devel space may also contain duplicate artifacts from the source space for non-standard catkin packages, whereas for standard catkin packages duplication is avoided. The target audience are users who want to build core ROS packages from source, rather than using pre-packaged distributions.
The first packages to be included as non-standard catkin packages like this are libraries like flann, kdl, opencv, pcl.
The build process catkin establishes bulk-processes all catkin projects within the same workspace folder as if they were part of a single CMake project. This design was chosen to speed up the configuration and build processes, and to allow for a single build space to allow easy cross-compilation. Rules exist for developers to follow to reduce the risk of undesired CMake namespace collisions between catkin packages (Some namespace collisions are desired to detect conflicts early that have to be resolved anyway).
Catkin also defines a devel space which acts like an install space in many respects. By complying to catkin rules for CMakeLists.txt, developers ensure that a catkin package can be deployed to a devel space properly. The devel space artifacts are generated by invoking the "make" command, with the default target (no 'install' necessary).
A non-standard catkin package does not use catkin macros (in particular not catkin_package, which is essential to the catkin workspace), so during it's configuration process it does not generate files for dependent packages to depend on it. This breaks the bulk-processing approach of the default catkin build process.
Instead, non-standard catkin projects can be supported by dropping the bulk processing approach for an isolated build approach. This configures and builds each package before configuring and building dependent packages.
This section reasons about alternative design choices and why they were rejected.
An option would have been to extend catkin_make with an option like --isolated. However the command line syntax between catkin_make and catkin_make_isolated varies somewhat, as well as the build result. However, currently discussed future changes to catkin_make might change this (consider catkin_cmake command).
The initial prototype of catkin_make_isolated invokes cmake and make for projects in sequence. Technically, it would be possible to parallelize this process for better performance when any 2 packages do not depend on each other. That's a technically valid alternative that may be implemented in the future, see:
The initial prototype of catkin_make_isolated provides an env.sh in the package's subfolder in the devel space to generate an environment such that dependencies can be found by CMake. With the prototype, the environment may also contain entries locating packages that were not listed as dependencies for a package, which may cause confusion and mask missing build information. It is thinkable to instead provide a way to set up a build environment that strictly only has entries for dependencies of a package from the workspace.
That's a technically valid alternative that may be implemented in the future, see:
A catkin_make_isolated command has been released with ROS Groovy.
This document has been placed in the public domain.