pkgs/top-level/stage.nix: add crossStdenv by RossComputerGuy · Pull Request #410056 · NixOS/nixpkgs

RossComputerGuy · 2025-05-23T06:52:54Z

Things done

Adds the new crossStdenv mechanism to be used inside nixpkgs instead of variants. Tested several armTrustedFirmware derivations as they appear on search and they compile fine.

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Aleksanaa · 2025-05-24T14:16:23Z

So

What's the final goal(s) of crossStdenv refactor?
How should we change our use cases of pkgsCross?

RossComputerGuy · 2025-05-24T14:28:39Z

Final goal is to provide cross compilation stdenv's which align with the pattern as described in #400351 (comment). These are purely the stdenv so eval will be smaller than bootstrapping another nixpkgs instance. As for pkgsCross, after this PR merges we will move everything off it it and move it to variants.

RossComputerGuy · 2025-05-25T01:57:33Z

Did a little benchmarking for musl on aarch64-linux.

`crossStdenv.configs.aarch64-unknown-linux-musl`

{
  "cpuTime": 0.43762001395225525,
  "envs": {
    "bytes": 5428488,
    "elements": 369695,
    "number": 308866
  },
  "gc": {
    "cycles": 1,
    "heapSize": 402915328,
    "totalBytes": 79396896
  },
  "list": {
    "bytes": 717400,
    "concats": 4609,
    "elements": 89675
  },
  "nrAvoided": 294217,
  "nrExprs": 135112,
  "nrFunctionCalls": 295668,
  "nrLookups": 152167,
  "nrOpUpdateValuesCopied": 2227726,
  "nrOpUpdates": 12343,
  "nrPrimOpCalls": 114176,
  "nrThunks": 263414,
  "sets": {
    "bytes": 42449136,
    "elements": 2626304,
    "number": 26767
  },
  "sizes": {
    "Attr": 16,
    "Bindings": 16,
    "Env": 8,
    "Value": 24
  },
  "symbols": {
    "bytes": 321885,
    "number": 32150
  },
  "time": {
    "cpu": 0.43762001395225525,
    "gc": 0.043000000000000003,
    "gcFraction": 0.09825876017793679
  },
  "values": {
    "bytes": 20363664,
    "number": 848486
  }
}

`pkgsMusl.stdenv`

{
  "cpuTime": 0.5026220083236694,
  "envs": {
    "bytes": 4656672,
    "elements": 324861,
    "number": 257223
  },
  "gc": {
    "cycles": 1,
    "heapSize": 402915328,
    "totalBytes": 125050816
  },
  "list": {
    "bytes": 601264,
    "concats": 4389,
    "elements": 75158
  },
  "nrAvoided": 262676,
  "nrExprs": 131023,
  "nrFunctionCalls": 242926,
  "nrLookups": 125858,
  "nrOpUpdateValuesCopied": 3930750,
  "nrOpUpdates": 13551,
  "nrPrimOpCalls": 104327,
  "nrThunks": 322854,
  "sets": {
    "bytes": 73163712,
    "elements": 4542912,
    "number": 29820
  },
  "sizes": {
    "Attr": 16,
    "Bindings": 16,
    "Env": 8,
    "Value": 24
  },
  "symbols": {
    "bytes": 320546,
    "number": 32025
  },
  "time": {
    "cpu": 0.5026220083236694,
    "gc": 0.07200000000000001,
    "gcFraction": 0.14324880090335151
  },
  "values": {
    "bytes": 32448624,
    "number": 1352026
  }
}

…ossChooser

…sChooser

Ericson2314 · 2025-05-25T05:30:22Z

I just want to reiterate that things being called "cross" today is entirely tech debt and should be gotten rid of. I would really like @NixOS/stdenv to help out @cloudripper who has taken on my GCC repackaging, so we can get rid of that entirely. I would feel more comfortable doing this sort of change after that, because we'd be working atop a better foundation.

RossComputerGuy · 2025-05-25T05:34:28Z

I don't really see how nixpkgs could function without being able to perform cross. I do agree that refactoring GCC would definitely help. I also think #365057 and #409851 (& similar) would definitely help out since we could make things more a part of the CC wrapper.

wolfgangwalther · 2025-07-20T11:12:17Z

Did a little benchmarking for musl on aarch64-linux.
crossStdenv.configs.aarch64-unknown-linux-musl
[..]
pkgsMusl.stdenv

Note that pkgsMusl is not a cross-setup. You probably need to compare against pkgsCross.aarch64-multiplatform-musl.

wolfgangwalther · 2025-07-20T11:12:58Z

Is crossStdenv also going to help to get rid of pkgsi686Linux?

wolfgangwalther

Why call this crossStdenv and not provide these nice attributes on stdenv directly?

stdenv.for.config.wasi32-unknown-wasi

Avoids the term "cross".

wolfgangwalther · 2025-07-20T11:19:01Z

doc/release-notes/rl-2511.section.md

+- A new cross compilation mechanism called `crossStdenv` has been added. It is recommended to use `crossStdenv` as
+  variants such as `pkgsCross`, `pkgsLLVM`, and `pkgsStatic` usage will no longer be permitted to be used in nixpkgs.


Although not used everywhere, yet, and unfortunately very hard to enforce via CI, we have a "one sentence per line" rule for docs:

https://github.com/NixOS/nixpkgs/blob/master/doc/README.md#one-sentence-per-line

Thus:

Suggested change

- A new cross compilation mechanism called `crossStdenv` has been added. It is recommended to use `crossStdenv` as

variants such as `pkgsCross`, `pkgsLLVM`, and `pkgsStatic` usage will no longer be permitted to be used in nixpkgs.

- A new cross compilation mechanism called `crossStdenv` has been added.

It is recommended to use `crossStdenv` as variants such as `pkgsCross`, `pkgsLLVM`, and `pkgsStatic` usage will no longer be permitted to be used in nixpkgs.

wolfgangwalther · 2025-07-20T11:23:33Z

doc/stdenv/cross-compilation.chapter.md

+#### How do I cross compile in nixpkgs? {#cross-qa-cross-compile-in-nixpkgs}
+Since NixOS 25.05, package sets such as `pkgsLLVM`, `pkgsMusl`, and `pkgsCross` have been moved into being labeled as variants. Future NixOS releases will disable the use of variants in nixpkgs. This is due to the increased evaluation since variants create a new nixpkgs instance atop the existing one. NixOS 24.11 introduces a feature called `crossStdenv`, this is a set of stdenv's for cross compiling without instantiating a new nixpkgs instance. `crossStdenv` contains a recursive attribute set called `predicated` and provides boolean options to a platform attribute set. It also contains `libcs` which is an attribute set of libc's that can be utilized. Finally, the recursive attribute set contains `configs` and `native`. `configs` is a set of attribute sets which contains stdenv's for each platform target that is supported for cross compiling. An example of the new pattern for something like `pkgsCross.wasi32.hello` would be:


Please use one sentence per line here, too, otherwise it's really hard to comment nicely on each sentence.

Suggested change

#### How do I cross compile in nixpkgs? {#cross-qa-cross-compile-in-nixpkgs}

Since NixOS 25.05, package sets such as `pkgsLLVM`, `pkgsMusl`, and `pkgsCross` have been moved into being labeled as variants. Future NixOS releases will disable the use of variants in nixpkgs. This is due to the increased evaluation since variants create a new nixpkgs instance atop the existing one. NixOS 24.11 introduces a feature called `crossStdenv`, this is a set of stdenv's for cross compiling without instantiating a new nixpkgs instance. `crossStdenv` contains a recursive attribute set called `predicated` and provides boolean options to a platform attribute set. It also contains `libcs` which is an attribute set of libc's that can be utilized. Finally, the recursive attribute set contains `configs` and `native`. `configs` is a set of attribute sets which contains stdenv's for each platform target that is supported for cross compiling. An example of the new pattern for something like `pkgsCross.wasi32.hello` would be:

#### How do I cross compile in nixpkgs? {#cross-qa-cross-compile-in-nixpkgs}

Since NixOS 25.05, package sets such as `pkgsLLVM`, `pkgsMusl`, and `pkgsCross` have been labeled as variants. Future NixOS releases will disallow the use of variants in nixpkgs. This is due to the increased evaluation time since each variant creates a new nixpkgs instance. NixOS 25.11 introduces `crossStdenv`, which is a set of stdenvs for cross compiling without instantiating a new nixpkgs instance. It contains a recursive attribute set `predicated` and provides boolean options to a platform attribute set. It also contains `libc` which is an attribute set of libcs that can be utilized. Finally, it contains `configs` and `native`. `configs` is a set of attribute sets which contains stdenvs for each platform target that is supported for cross compiling. An example of the new pattern for something like `pkgsCross.wasi32.hello` would be:

(I put a few smaller changes in this, but it won't be highlighted due to everything being on one line here ... :/)

It mentions native but doesn't explain it.

wolfgangwalther · 2025-07-20T11:24:45Z

doc/stdenv/cross-compilation.chapter.md

+}
+```
+
+Note that the `stdenv` is overridden to provide the `wasi32-unknown-wasi` stdenv with the `useLLVM` predicate enabled. It is important to override all runtime dependencies to ensure the package properly cross compiles.


Suggested change

Note that the `stdenv` is overridden to provide the `wasi32-unknown-wasi` stdenv with the `useLLVM` predicate enabled. It is important to override all runtime dependencies to ensure the package properly cross compiles.

Note that `stdenv` is overridden to provide the `wasi32-unknown-wasi` stdenv with the `useLLVM` predicate enabled.

It is important to override all runtime dependencies to ensure the package properly compiles.

wolfgangwalther · 2025-07-20T11:30:48Z

pkgs/top-level/cross-stdenv.nix

+    "musl"
+    "glibc"
+    "newlib"
+    "newlib-nano"
+    "msvcrt"
+    "ucrt"


People will add stuff over time and it always confuses me. Where do I add this?

Might as well sort alphabetically instead of randomly:

Suggested change

"musl"

"glibc"

"newlib"

"newlib-nano"

"msvcrt"

"ucrt"

"glibc"

"msvcrt"

"musl"

"newlib"

"newlib-nano"

"ucrt"

wolfgangwalther · 2025-07-20T11:30:56Z

pkgs/top-level/cross-stdenv.nix

+  predicates = [
+    "useLLVM"
+    "isStatic"
+  ];


Suggested change

predicates = [

"useLLVM"

"isStatic"

];

predicates = [

"isStatic"

"useLLVM"

];

wolfgangwalther · 2025-07-20T11:32:18Z

pkgs/top-level/cross-stdenv.nix

+  configs = [
+    "avr"
+    "aarch64-unknown-linux-gnu"
+    "aarch64-unknown-linux-musl"
+    "armv7l-unknown-linux-gnueabihf"
+    "arm-none-eabi"
+    "i686-unknown-linux-gnu"
+    "i686-w64-mingw32"
+    "s390-unknown-linux-gnu"
+    "s390x-unknown-linux-gnu"
+    "riscv32-unknown-linux-gnu"
+    "riscv32-unknown-linux-musl"
+    "riscv64-unknown-linux-gnu"
+    "riscv64-unknown-linux-musl"
+    "wasm32-unknown-none"
+    "wasm32-unknown-wasi"
+    "x86_64-unknown-linux-gnu"
+    "x86_64-unknown-linux-musl"
+    "x86_64-w64-mingw32"
+  ];


Suggested change

configs = [

"avr"

"aarch64-unknown-linux-gnu"

"aarch64-unknown-linux-musl"

"armv7l-unknown-linux-gnueabihf"

"arm-none-eabi"

"i686-unknown-linux-gnu"

"i686-w64-mingw32"

"s390-unknown-linux-gnu"

"s390x-unknown-linux-gnu"

"riscv32-unknown-linux-gnu"

"riscv32-unknown-linux-musl"

"riscv64-unknown-linux-gnu"

"riscv64-unknown-linux-musl"

"wasm32-unknown-none"

"wasm32-unknown-wasi"

"x86_64-unknown-linux-gnu"

"x86_64-unknown-linux-musl"

"x86_64-w64-mingw32"

];

configs = [

"aarch64-unknown-linux-gnu"

"aarch64-unknown-linux-musl"

"arm-none-eabi"

"armv7l-unknown-linux-gnueabihf"

"avr"

"i686-unknown-linux-gnu"

"i686-w64-mingw32"

"riscv32-unknown-linux-gnu"

"riscv32-unknown-linux-musl"

"riscv64-unknown-linux-gnu"

"riscv64-unknown-linux-musl"

"s390-unknown-linux-gnu"

"s390x-unknown-linux-gnu"

"wasm32-unknown-none"

"wasm32-unknown-wasi"

"x86_64-unknown-linux-gnu"

"x86_64-unknown-linux-musl"

"x86_64-w64-mingw32"

];

wolfgangwalther · 2025-07-20T11:33:22Z

pkgs/top-level/cross-stdenv.nix

+    configs = mkConfigSet platform;
+    predicated = mkPredicatedSet platform;
+    libc = mkLibcSet platform;
+    native = overrideStdenv (


libc is singular (although the docs currently say libcs) and configs is plural.

We only select a single one at any given point, so I think both should be singular.

Suggested change

configs = mkConfigSet platform;

predicated = mkPredicatedSet platform;

libc = mkLibcSet platform;

native = overrideStdenv (

config = mkConfigSet platform;

predicated = mkPredicatedSet platform;

libc = mkLibcSet platform;

native = overrideStdenv (

philiptaron · 2025-09-12T00:48:41Z

Tristan, this PR looks blocked on your response to feedback. I'm marking it as draft until you've got the cycles to unblock it.

github-actions bot added the 6.topic: stdenv Standard environment label May 23, 2025

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RossComputerGuy force-pushed the feat/cross-stdenv branch 3 times, most recently from 33c476e to 2039bbf Compare May 23, 2025 07:10

github-actions bot added 10.rebuild-darwin: 1 This PR causes 1 package to rebuild on Darwin. 10.rebuild-darwin: 1-10 This PR causes between 1 and 10 packages to rebuild on Darwin. 10.rebuild-linux: 11-100 This PR causes between 11 and 100 packages to rebuild on Linux. labels May 23, 2025

RossComputerGuy force-pushed the feat/cross-stdenv branch 2 times, most recently from 97a57cc to 8f22062 Compare May 24, 2025 02:28

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pkgs/top-level/all-packages.nix: add cxxlibCross & cxxlibCrossChooser

f35606d

pkgs/top-level/all-packages.nix: add unwinderlibCross & unwinderlibCr…

53e6116

…ossChooser

pkgs/top-level/all-packages.nix: add rtlibCross & rtlibCrossChooser

8aa9ba7

pkgs/top-level/all-packages.nix: add ccCross & ccCrossChooser

016bb55

pkgs/top-level/all-packages.nix: make bintools-unwrapped into bintool…

52f7c7e

…sChooser

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glibc: allow override of linuxHeaders

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RossComputerGuy added 6 commits May 24, 2025 23:09

pkgs/top-level/stage.nix: add crossStdenv

8969728

doc/stdenv/cross-compilation: Add section for crossStdenv

cb8e53e

doc/rl2511: mention crossStdenv in favor over pkgsCross

0be7afc

armTrustedFirmware: use crossStdenv instead of pkgsCross

f561a26

klipper: use crossStdenv instead of pkgsCross

11e5030

box64: make hello-x86_64 use crossStdenv

bb0d35d

RossComputerGuy force-pushed the feat/cross-stdenv branch from 1a513fc to bb0d35d Compare May 25, 2025 06:09

RossComputerGuy mentioned this pull request Jun 5, 2025

libcCross: Remove! #414321

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RossComputerGuy mentioned this pull request Jul 6, 2025

mlibc: init at 6.2.0-unstable-2025-10-08 #371092

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RossComputerGuy mentioned this pull request Jul 18, 2025

pkgs/top-level/stage.nix: move most nixpkgs sets to variants #400351

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wolfgangwalther reviewed Jul 20, 2025

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wolfgangwalther mentioned this pull request Jul 20, 2025

ci/eval: fail on asserts when generating attrpaths #426629

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philiptaron marked this pull request as draft September 12, 2025 00:48

		- A new cross compilation mechanism called `crossStdenv` has been added. It is recommended to use `crossStdenv` as
		variants such as `pkgsCross`, `pkgsLLVM`, and `pkgsStatic` usage will no longer be permitted to be used in nixpkgs.

		#### How do I cross compile in nixpkgs? {#cross-qa-cross-compile-in-nixpkgs}
		Since NixOS 25.05, package sets such as `pkgsLLVM`, `pkgsMusl`, and `pkgsCross` have been moved into being labeled as variants. Future NixOS releases will disable the use of variants in nixpkgs. This is due to the increased evaluation since variants create a new nixpkgs instance atop the existing one. NixOS 24.11 introduces a feature called `crossStdenv`, this is a set of stdenv's for cross compiling without instantiating a new nixpkgs instance. `crossStdenv` contains a recursive attribute set called `predicated` and provides boolean options to a platform attribute set. It also contains `libcs` which is an attribute set of libc's that can be utilized. Finally, the recursive attribute set contains `configs` and `native`. `configs` is a set of attribute sets which contains stdenv's for each platform target that is supported for cross compiling. An example of the new pattern for something like `pkgsCross.wasi32.hello` would be:

	Note that the `stdenv` is overridden to provide the `wasi32-unknown-wasi` stdenv with the `useLLVM` predicate enabled. It is important to override all runtime dependencies to ensure the package properly cross compiles.
	Note that `stdenv` is overridden to provide the `wasi32-unknown-wasi` stdenv with the `useLLVM` predicate enabled.
	It is important to override all runtime dependencies to ensure the package properly compiles.

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RossComputerGuy commented May 23, 2025

Things done

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Aleksanaa commented May 24, 2025

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RossComputerGuy commented May 24, 2025

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RossComputerGuy commented May 25, 2025

crossStdenv.configs.aarch64-unknown-linux-musl

pkgsMusl.stdenv

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`crossStdenv.configs.aarch64-unknown-linux-musl`

`pkgsMusl.stdenv`

wolfgangwalther commented Jul 20, 2025 •

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