fast enable/distable distcc

mortonP · Tux's lil' helper Joined: 22 Dec 2015 Posts: 89

I use an underpowered laptop, but I got a distcc setup running, and compiling chromium with distcc workers drops compile time massively - yay! :-)

Problem is, with my laptop I'm moving around, so when I'm at home I have to compile locally, when I'm at a specific site I can use the extra, unused PCs there and on them VMs with Gentoo as workers...
Now I'm manually editing /etc/portage/make.conf, FEATURES for +distcc and MAKEOPTS to adjust -jx -l2y, and start distcc service.

Questions: Is there a more convenient way to do enable/disable this? Maybe an "emerge --distcc ...." option or something like that, to prevent always editing config files?

Thank you!

Genone · Posted: Thu Oct 20, 2022 9:42 am Post subject:

Just add a function in your .profile:

mortonP · Tux's lil' helper Joined: 22 Dec 2015 Posts: 89

That's a good idea - put it into /root/.bashrc with my other custom stuff:

Hu · Administrator Joined: 06 Mar 2007 Posts: 22730

Genone specifically wrote FEATURES="$FEATURES features-you-want" so that any preexisting FEATURES environment variable would influence the resulting emerge. Your rewritten version replaces, rather than augments, $FEATURES. Therefore:

Massimo B. · Posted: Thu Nov 17, 2022 7:24 am Post subject:

Hi, I have taken your approach defining an emerge-distcc function into my How to share /etc/portage and world file.
This is not only setting FEATURES for distcc but also different CFLAGS to have explicit -march= instead of native. However I wonder that CXXFLAGS also needs to be set although already defined as CXXFLAGS="${CFLAGS}": https://forums.gentoo.org/viewtopic-p-8759259.html#8759259
Any idea why this is the case?
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Genone · Posted: Thu Nov 17, 2022 8:07 am Post subject:

Simple: The CXXFLAGS=$CFLAGS substitution takes place when the corresponding config file is parsed. If you then later override CFLAGS the content of CXXFLAGS no longer references CFLAGS. And that is how it should be.

Massimo B. · Posted: Thu Nov 17, 2022 8:24 am Post subject:

Genone · Posted: Thu Nov 17, 2022 9:16 am Post subject:

The substitution is done by portage itself when parsing the config, the build environment is not involved there and only ever sees the final result. Basically the same if you run "source make.conf" manually.

I'm not exactly sure which syntax elements are supported by portage these days, so if you really want to you may be able to bypass it using a syntax not supported by portage but only the actual shell, e.g. CXXFLAGS="\$(echo \$CFLAGS)" (again, no idea how portage will actually react to that, may take some trial-and-error to figure out the details).

Note that USE and some other special (so-called incremental) variables are treated a bit different, but those are limited to things affecting portage itself. For normal variables the last definition simply overwrites a previous one.