The other day, I ran was unable to rebuild my NixOS configuration due to a problem with thermald:
$ sudo nixos-rebuild switch
...
Making all in .
make[2]: Entering directory '/build/source'
CXX src/thermald-main.o
CXX src/thermald-thd_dbus_interface.o
CXX src/thermald-thd_engine.o
CXX src/thermald-thd_cdev.o
CXX src/thermald-thd_cdev_therm_sys_fs.o
CXX src/thermald-thd_engine_default.o
CXX src/thermald-thd_engine_adaptive.o
src/thd_engine_adaptive.cpp: In member function 'int cthd_engine_adaptive::evaluate_lid_condition(condition)':
src/thd_engine_adaptive.cpp:1002:61: error: 'gboolean up_client_get_lid_is_closed(UpClient*)' is deprecated [8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wdeprecated-declarations-Werror=deprecated-declarations8;;]
1002 | bool lid_closed = up_client_get_lid_is_closed(upower_client);
| ^
In file included from /nix/store/20mc2h51sw8kgj5igfm74pqcpb5g4zsm-upower-0.99.15-dev/include/libupower-glib/upower.h:38,
from src/thd_engine_adaptive.h:30,
from src/thd_engine_adaptive.cpp:32:
/nix/store/20mc2h51sw8kgj5igfm74pqcpb5g4zsm-upower-0.99.15-dev/include/libupower-glib/up-client.h:98:11: note: declared here
98 | gboolean up_client_get_lid_is_closed (UpClient *client);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
make[2]: *** [Makefile:903: src/thermald-thd_engine_adaptive.o] Error 1
make[2]: Leaving directory '/build/source'
make[1]: *** [Makefile:1463: all-recursive] Error 1
make[1]: Leaving directory '/build/source'
make: *** [Makefile:559: all] Error 2
error: builder for '/nix/store/3qrj9qxpn2fc6hp0qnmksb6zpn5dsvv8-thermald-2.4.8.drv' failed with exit code 2
error: 1 dependencies of derivation '/nix/store/yqskvlpan0ylpckn8h760jlmy0jy5xrj-dbus-1.drv' failed to build
error: 1 dependencies of derivation '/nix/store/948n7w885c6l73rl21vj93pahrz9mml8-unit-thermald.service.drv' failed to build
error: 1 dependencies of derivation '/nix/store/0h9ph1piccc8lij4ykfcb4bd9k27pvv4-etc.drv' failed to build
error: 1 dependencies of derivation '/nix/store/mmzg752mpry5h13x6h8wcm7g31bz4g9p-nixos-system-nixos-22.05pre358459.3e072546ea9.drv' failed to build
This isn't good.
I went to https://github.com/NixOS/nixpkgs/issues and searched for thermald, and sure enough I found this: https://github.com/NixOS/nixpkgs/pull/162568
It looked like someone already had the solution - append --disable-werror to the compilation flags.
But how long until this patch arrived in my channel, nixos-unstable? I had rebuilt multiple times over the past few days and hadn't seen the change.
So, I decided to see if I could apply this patch myself. I knew https://nixos.wiki/wiki/Overlays were a thing but I never used them.
Anyway, long story short, I looked at the Files changed tab, and saw that the patch was targeting thermald/default.nix with this change:
configureFlags = [
"--sysconfdir=${placeholder "out"}/etc"
"--localstatedir=/var"
"--enable-gtk-doc"
"--with-dbus-sys-dir=${placeholder "out"}/share/dbus-1/system.d"
"--with-systemdsystemunitdir=${placeholder "out"}/etc/systemd/system"
"--disable-werror"
];
I discovered that I didn't have to wait for this patch to arrive, I could apply this change myself to my local configuration file, and get the patch early:
In configuration.nix, I added the following:
nixpkgs.overlays = [ (self: super:
{
thermald = super.thermald.overrideAttrs (old: {
configureFlags = old.configureFlags ++ [ "--disable-werror" ];
});
}
)];
And it was successful!
To be honest the overlay mechanism is still a bit opaque to me, I understand that what I'm doing above is appending an extra build flag to the existing thermald derivation, but I'm still not very comfortable with the functional syntax.
Anyway, it worked.