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3rd chunk of `doc/manual/source/development/building.md`
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When cross-compiling Nix with Meson for local development, you need to specify a [cross-file](https://mesonbuild.com/Cross-compilation.html) using the `--cross-file` option. Cross-files define the target architecture and toolchain. When cross-compiling Nix with Nix, Nixpkgs takes care of this for you.

In the nix flake we also have some cross-compilation targets available:

```
nix build .#nix-everything-riscv64-unknown-linux-gnu
nix build .#nix-everything-armv7l-unknown-linux-gnueabihf
nix build .#nix-everything-armv7l-unknown-linux-gnueabihf
nix build .#nix-everything-x86_64-unknown-freebsd
nix build .#nix-everything-x86_64-w64-mingw32
```

For historic reasons and backward-compatibility, some CPU and OS identifiers are translated as follows:

| `config.guess`             | Nix                 |
|----------------------------|---------------------|
| `amd64`                    | `x86_64`            |
| `i*86`                     | `i686`              |
| `arm6`                     | `arm6l`             |
| `arm7`                     | `arm7l`             |
| `linux-gnu*`               | `linux`             |
| `linux-musl*`              | `linux`             |

## Compilation environments

Nix can be compiled using multiple environments:

- `stdenv`: default;
- `gccStdenv`: force the use of `gcc` compiler;
- `clangStdenv`: force the use of `clang` compiler;
- `ccacheStdenv`: enable [ccache], a compiler cache to speed up compilation.

To build with one of those environments, you can use

```console
$ nix build .#nix-cli-ccacheStdenv
```

for flake-enabled Nix, or

```console
$ nix-build --attr nix-cli-ccacheStdenv
```

for classic Nix.

You can use any of the other supported environments in place of `nix-cli-ccacheStdenv`.

## Editor integration

The `clangd` LSP server is installed by default on the `clang`-based `devShell`s.
See [supported compilation environments](#compilation-environments) and instructions how to set up a shell [with flakes](#nix-with-flakes) or in [classic Nix](#classic-nix).

To use the LSP with your editor, you will want a `compile_commands.json` file telling `clangd` how we are compiling the code.
Title: Compilation Environments and Editor Integration in Nix
Summary
This section describes different compilation environments available for building Nix, including `stdenv`, `gccStdenv`, `clangStdenv`, and `ccacheStdenv`. It explains how to use these environments with both flake-enabled and classic Nix. Furthermore, it discusses editor integration, specifically the inclusion of the `clangd` LSP server in `clang`-based development shells and the need for a `compile_commands.json` file.