nix-super/doc/manual/rl-next/build-hook-default.md

---
synopsis: |-
  The `build-hook` setting's default is less useful when using `libnixstore` as a library
prs:
- 11178
---

*This is an obscure issue that only affects usage of the `libnixstore` library outside of the Nix executable.*

As part the ongoing [rewrite of the build system](https://github.com/NixOS/nix/issues/2503) to use [Meson](https://mesonbuild.com/), we are also switching to packaging individual Nix components separately (and building them in separate derivations).
This means that when building `libnixstore` we do not know where the Nix binaries will be installed --- `libnixstore` doesn't know about downstream consumers like the Nix binaries at all.

*This is also unrelated to the _`post`_-`build-hook`*, which is often used for pushing to a cache.*

This has a small adverse affect on remote building --- the `build-remote` executable that is specified from the [`build-hook`](@docroot@/command-ref/conf-file.md#conf-build-hook) setting will not be gotten from the (presumed) installation location, but instead looked up on the `PATH`.
This means that other applications linking `libnixstore` that wish to use remote building must arrange for the `nix` command to be on the PATH (or manually overriding `build-hook`) in order for that to work.

Long term we don't envision this being a downside, because we plan to [get rid of `build-remote` and the build hook setting entirely](https://github.com/NixOS/nix/issues/1221).
There is simply no need to add a second layer of remote-procedure-calling when we want to connect to a remote builder.
The build hook protocol did in principle support custom ways of remote building, but that can also be accomplished with a custom service for the ssh or daemon/ssh-ng protocols, or with a custom [store type](@docroot@/store/types/) i.e. `Store` subclass. <!-- we normally don't mention classes, but consider that this release note is about a library use case -->

The Perl bindings no longer expose `getBinDir` either, since they libraries those bindings wrap no longer know the location of installed binaries as described above.
Move `NIX_BIN_DIR` and all logic using it to the Nix executable itself This is because with the split packages of the Meson build, we simply have no idea what directory the binaries will be installed in when we build the library. In the process of doing so, consolidate and make more sophisticated the logic to cope with a few corner cases (e.g. `NIX_BIN_DIR` exists, but no binaries are inside it). Co-authored-by: Robert Hensing <roberth@users.noreply.github.com> 2024-07-25 06:14:36 +03:00			`---`
			`synopsis: \|-`
			The `build-hook` setting's default is less useful when using `libnixstore` as a library
			`prs:`
			`- 11178`
			`---`

			This is an obscure issue that only affects usage of the `libnixstore` library outside of the Nix executable.

			`As part the ongoing [rewrite of the build system](https://github.com/NixOS/nix/issues/2503) to use [Meson](https://mesonbuild.com/), we are also switching to packaging individual Nix components separately (and building them in separate derivations).`
			This means that when building `libnixstore` we do not know where the Nix binaries will be installed --- `libnixstore` doesn't know about downstream consumers like the Nix binaries at all.

			This is also unrelated to the _`post`_-`build-hook`, which is often used for pushing to a cache.*

			This has a small adverse affect on remote building --- the `build-remote` executable that is specified from the [`build-hook`](@docroot@/command-ref/conf-file.md#conf-build-hook) setting will not be gotten from the (presumed) installation location, but instead looked up on the `PATH`.
			This means that other applications linking `libnixstore` that wish to use remote building must arrange for the `nix` command to be on the PATH (or manually overriding `build-hook`) in order for that to work.

			Long term we don't envision this being a downside, because we plan to [get rid of `build-remote` and the build hook setting entirely](https://github.com/NixOS/nix/issues/1221).
			`There is simply no need to add a second layer of remote-procedure-calling when we want to connect to a remote builder.`
			The build hook protocol did in principle support custom ways of remote building, but that can also be accomplished with a custom service for the ssh or daemon/ssh-ng protocols, or with a custom [store type](@docroot@/store/types/) i.e. `Store` subclass. <!-- we normally don't mention classes, but consider that this release note is about a library use case -->

			The Perl bindings no longer expose `getBinDir` either, since they libraries those bindings wrap no longer know the location of installed binaries as described above.