Niels Thykier: Introducing the debhelper buildlabel prototype for multi-building packages
For most packages, the dh short-hand rules (possibly with a few overrides) work great. It can often auto-detect the buildsystem and handle all the trivial parts.
With one notably exception: What if you need to compile the upstream code twice (or more) with different flags? This is the case for all source packages building both regular debs and udebs.
In that case, you would previously need to override about 5-6 helpers for this to work at all. The five dh_auto_* helpers and usually also dh_install (to call it with different sourcedir for different packages). This gets even more complex if you want to support Build-Profiles such as noudeb and nodoc .
The best way to support nodoc in debhelper is to move documentation out of dh_install s config files and use dh_installman, dh_installdocs, and dh_installexamples instead (NB: wait for compat 11 before doing this). This in turn will mean more overrides with sourcedir and -p/-N.
And then there is noudeb , which currently requires manual handling in debian/rules. Basically, you need to use make or shell if-statements to conditionally skip the udeb part of the builds.
All of this is needlessly complex.
Improving the situation
In an attempt to make things better, I have made a new prototype feature in debhelper called buildlabels in experimental. The current prototype is designed to deal with part (but not all) of the above problems:
Filed under: Debhelper, Debian
- It will remove the need for littering your rules file for supporting noudeb (and in some cases also other noX profiles).
- It will remove the need for overriding the dh_install* tools just to juggle with sourcedir and -p/-N.
- foo
- libfoo1
- libfoo-dev
- foo-udeb
- libfoo1-udeb
[...]
override_dh_auto_configure:
dh_auto_configure -B build-deb -- --with-feature1 --with-feature2
dh_auto_configure -B build-udeb -- --without-feature1 --without-feature2
[...]
What is somewhat obvious to a human is that the first configure line is related to the regular debs and the second configure line is for the udebs. However, debhelper does not know how to infer this and this is where buildlabels come in. With buildlabels, you can let debhelper know which packages and builds that belong together.
How to use buildlabels
To use buildlabels, you have to do three things:
- Pick a reasonable label name for the secondary build. In the example, I will use udeb .
- Add buildlabel=$LABEL to all dh_auto_* calls related to your secondary build.
- Tag all packages related to my-label with X-DH-Buildlabel: $LABEL in debian/control. (For udeb packages, you may want to add Build-Profiles: <!noudeb> while you are at it).
[...]
override_dh_auto_configure:
dh_auto_configure -B build-deb -- --with-feature1 --with-feature2
dh_auto_configure --buildlabel=udeb -B build-udeb -- --without-feature1 --without-feature2
[...]
(Remember to update *all* calls to dh_auto_* helpers; the above only lists dh_auto_configure to keep the example short.) And then add X-DH-Buildlabel: udeb in the stanzas for foo-udeb + libfoo1-udeb.
With those two minor changes:
- debhelper will skip the calls to dh_auto_* with buildlabel=udeb if the udeb packages are skipped.
- dh_auto_install will automatically pick a separate destination directory by default for the udeb build (assuming you do not explicitly override it with destdir).
- dh_install will now automatically pick up files from the destination directory.that dh_auto_install used for the given package (even if you overwrote it with destdir). Note that you have to remove any use of sourcedir first as this disables the auto-detection. This also works for other dh_install* tools supporting sourcedir in compat 11 or later.
- Apply labels to packages and dh_auto_* tools: https://anonscm.debian.org/git/pkg-systemd/systemd.git/commit/?h=wip-dh-prototype-smarter-multi-builds&id=880a80bc392a298bed033c047ccbef65e50acc58
- Clean up most make conditionals: https://anonscm.debian.org/git/pkg-systemd/systemd.git/commit/?h=wip-dh-prototype-smarter-multi-builds&id=96c0ab8b35ce04eab031a4a9ee4c4ef686f76977
- Merge multiple dh_install calls into one: https://anonscm.debian.org/git/pkg-systemd/systemd.git/commit/?h=wip-dh-prototype-smarter-multi-builds&id=67994cb5e5b451ebcebb0dccfdd97e606ac4a172
( fail-missing was never applied to the udeb before; I kept it that way by passing sourcedir to dh_missing because I was to lazy to review the missing files).
- It is experimental feature and may change without notice.
- The current prototype may break existing packages as it is not guarded by a compat bump to ease your testing. I am still very curious to hear about any issues you may experience.
- The default build directory is re-used even with different buildlabels, so you still need to use explicit build dirs for buildsystems that prefer building in a separate directory (e.g. meson).
- udebs are not automatically tagged with an udeb buildlabel. This is partly by design as some source packages only build udebs (and no regular debs). If they were automatically tagged, the existing packages would break.
- Label names are used in path names, so you may want to refrain from using too exciting label names.
- It is experimental feature and may change without notice. (Yes, I thought it deserved repeating)
Filed under: Debhelper, Debian
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