devo - Developer Overlay

Devo is a system to define custom environments to build and install software using different settings.

The idea is to define separate build and install dirs, in your home dir.

Here is an example of what the dir hierarchy could look like:

$HOME/
    src
        libfoo
        fooserver
        bar
    build
        overlay1
            libfoo
            fooserver
        overlay2
            bar
    install
        overlay1
            bin
            share
            lib
            ...
        overlay2
            bin
            share
            lib
            ...

With such a setup, one could start a shell on using overlay1 like this:

devo_sh overlay1

After this command, assuming overlay1 has been correctly set up, $HOME/install/overlay1/bin would be in $PATH, making it possible to run software installed there.

If libfoo uses the CMake build system, one can then build it with:

cd $HOME/build/overlay1/libfoo
devo_cmake
make
make install

Devo also provides handy commands to switch dirs, devo_cb changes to the build dir, devo_cs changes to the source dir.

cd $HOME/src/libfoo

devo_cb
# $PWD is now $HOME/build/overlay1/libfoo

devo_cs
# $PWD is now $HOME/src/libfoo

devo_cmake is also smart enough to run in the build dir, and Devo comes with a thin wrapper for make: devo_make which brings build dir awareness as well, so one can also build libfoo like this:

cd $HOME/src/libfoo
devo_cmake
devo_make
devo_make install

Variables used by Devo

• $DEVO_NAME: The name of the overlay ("overlay1" or "overlay2")

• $DEVO_SOURCE_BASE_DIR: Where source is stored ($HOME/src). Can be common, or specific to an overlay.

• $DEVO_BUILD_BASE_DIR: Where build dirs for component will be created ($HOME/build/overlay1)

• $DEVO_BUILD_BASE_ROOT_DIR: The dir which contains all $DEVO_BUILD_BASE_DIR ($HOME/build)

• $DEVO_PREFIX: The dir where components will be installed ($HOME/install/overlay1)

Initial setup

First, create the ~/.devo/ dir. This dir will contain all the overlay definitions.

Next create a file named ~/.devo/_base. This file is loaded before activating any overlay. Define the DEVO_BUILD_BASE_ROOT_DIR in it:

export DEVO_BUILD_BASE_ROOT_DIR=/path/to/build/root/dir

Finally, add the following lines to your shell:

. /path/to/devo/lib/devo/devo-setup.source

Creating an overlay

Create an overlay file in ~/.devo/. The file name is used as the overlay name. This file is a shell script which should at least define the following variables:

• $DEVO_PREFIX
• $DEVO_SOURCE_BASE_DIR

It may also define:

• $DEVO_CMAKE_BUILD_TYPE: Build type argument passed by devo_cmake to cmake.

And other variables relevant for your environment:

• $PATH
• $PKG_CONFIG_PATH
• ...

Devo also provides some shell functions which can be used in overlay files:

• _devo_prepend_prefix <arg>: assume $arg is an install prefix and prepend its sub dirs ($arg/bin, $arg/lib...) to $PKG_CONFIG_PATH, $LD_LIBRARY_PATH, $CMAKE_PREFIX_PATH, $PATH and $PYTHONPATH.

• _devo_prepend_path <arg>: shortcut for export PATH=$arg:$PATH.

• _devo_append_path <arg>: shortcut for export PATH=$PATH:$arg.

Tools

devo_sh

Starts a new shell with the specified overlay loaded:

devo_sh work

Starts a new shell with the "work" overlay. Leave the shell with Ctrl+D or exit to unload all the changes.

devo_setup

Loads an overlay in the current shell:

devo_setup work

Loads the "work" overlay.

devo_cmake

Run cmake with the right prefix and build type option. Usage:

devo_cmake /path/to/source/dir

When run without an argument, it tries to figure out the source dir using $DEVO_SOURCE_BASE_DIR and the base name of the current dir.

For example if you run devo_cmake from dir $DEVO_BUILD_BASE_DIR/foo, it will use $DEVO_SOURCE_BASE_DIR/foo as the source dir.

devo_make

Wrapper around make: switch to the build dir and runs make from there.

If there is no Makefile file in the build dir, but there is one file whose name starts with Makefile, uses this file instead.

devo_run

Run a command using a specific overlay:

devo_run work mytool arg1 arg2

Loads the "work" overlay and runs mytool arg1 arg2.

devo_cb

When in a source dir, change to the matching build dir.

If a matching build dir does not exist, try to find an existing parent build dir, for example given this setup:

$DEVO_SOURCE_BASE_DIR
    prj1
        foo

$DEVO_BUILD_BASE_DIR
    prj1

If you are in $DEVO_SOURCE_BASE_DIR/prj1/foo, devo_cb will switch to $DEVO_BUILD_BASE_DIR/prj1.

If no build dir can be found but user is in a source dir, devo_cb offers to create it.

When outside of a source dir, devo_cb prints an error.

devo_cs

When in a build dir, change to the matching source dir if it exists, otherwise stays there.

Interesting variables to set in ~/.devo/_base

Since ~/.devo/_base is sourced before loading a new overlay, you can define a base environment in it, for example you can define a base value for $PATH or for $CC and $CXX.

Shell integration goodies

When an overlay is loaded, the $DEVO_NAME variable contains its name. It can be handy to add this to your prompt.

Zsh users can add the following to their .zshrc:

cd() {
    builtin cd $*
    devo_setup_from_pwd
}

This makes Devo load the matching overlay when cd-ing to an overlay build dir.

TODO: Find the bash equivalent