cmake: setup-hooks: take structural `cmakeEntries` by ShamrockLee · Pull Request #442017 · NixOS/nixpkgs

ShamrockLee · 2025-09-11T11:25:56Z

This PR provides structural access to the CMake flags specifying CMake variable cache entries.

If applied, we'll be able to do

{
  stdenv,
  cmake,
}:
stdenv.mkDerivation {
  __structuredAttrs = true;
  nativeBuildInputs = [ cmake ];
  cmakeEntries = {
    CMAKE_BUILD_TYPE = "RelWithDebInfo";
    WITH_PYTHON_BINDINGS = false;
  };
}

Aside from

{
  lib,
  stdenv,
  cmake,
}:
stdenv.mkDerivation {
  nativeBuildInputs = [ cmake ];
  cmakeFlags = [
    (lib.cmakeFeature "CMAKE_BUILD_TYPE" "RelWithDebInfo")
    (lib.cmakeBool "WITH_PYTHON_BINDINGS" false)
  ];
}

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LunNova · 2025-09-11T12:28:19Z

How important is being able to set :BOOL automatically?

ShamrockLee · 2025-09-11T12:46:21Z

How important is being able to set :BOOL automatically?

The flag would be more human-readable. If cmakeDefinitionTypes[WITH_FOO]=BOOL is set, the resulting flag would be -DWITH_FOO:BOOL=ON instead of -DWITH_FOO=1 (or -DWITH_FOO:BOOL=OFF instead of -DWITH_FOO=)

In the mean time, I'm also considering if we should auto-convert

{
  # WITH_FOO takes, e.g., "auto", true-like, and false-like
  cmakeDefinitions.WIITH_FOO = true;
  cmakeDefinitionTypes.WITH_FOO = "STRING";
}

to cmakeDefinitions[WITH_FOO]=ON (instead of cmakeDefinitions[WITH_FOO]="").

Update: Just implemented the above feature.

ShamrockLee · 2025-09-11T18:29:07Z

-GNinja
@ofborg build aws-lc
@ofborg build bencode

nixos-discourse · 2025-09-11T19:45:56Z

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/structured-cmakeflags-attrs/6261/5

RossSmyth

Love the idea, I'd love to see this in-tree. Unsure about the two disconnected attrset API, but it works well enough.

pkgs/by-name/cm/cmake/setup-hook.sh

ShamrockLee · 2025-11-03T11:24:18Z

Sorry for the wrong rebase. Fell free to unsubscribe.

All good now, thank you!

ShamrockLee · 2025-11-03T11:35:09Z

I simplified the implementation and dropped cmakeEntryTypes.

Now, CMake boolean values are expected to be either cmakeEntries[enableFoo] == ON or cmakEntries[enableFoo] == OFF. Values from { cmakeEntries.enableFoo = true; } will be canonicalized at the setup-hook source time. Other supported values supported by CMake are also acceptable. Helper Bash functions canonicalizeCMakeBool, cmakeBoolToBash, and testCMakeBool helps users handle them.

ShamrockLee · 2025-11-03T17:05:15Z

`nixpkgs-review` result

Generated using nixpkgs-review-gha

Command: nixpkgs-review pr 442017 -p cmakeMinimal -p cmake -p bcc
Commit: 182e3ab18e0da37cd575c8dd823a8dc968b8128d (subsequent changes)
Merge: 5ccef07aff19527b94145ca080d073effd244e03

Logs: https://github.com/ShamrockLee/nixpkgs-review-gha/actions/runs/19035963338

`x86_64-linux`

❌ 2 packages failed to build:

bcc
bcc.man (bcc.man.man)

✅ 4 packages built:

cmake
cmake.debug (cmake.debug.debug)
cmakeMinimal
cmakeMinimal.debug (cmakeMinimal.debug.debug)

`aarch64-linux`

❌ 2 packages failed to build:

bcc
bcc.man (bcc.man.man)

✅ 4 packages built:

cmake
cmake.debug (cmake.debug.debug)
cmakeMinimal
cmakeMinimal.debug (cmakeMinimal.debug.debug)

`x86_64-darwin` (sandbox = relaxed)

❌ 2 packages failed to build:

cmake
cmakeMinimal

`aarch64-darwin` (sandbox = relaxed)

❌ 2 packages failed to build:

cmake
cmakeMinimal

ttuegel · 2025-11-03T23:59:31Z

doc/hooks/cmake.section.md

@@ -16,9 +16,35 @@ You can disable this hook’s behavior by setting `configurePhase` to a custom v

 ### CMake Exclusive Variables {#cmake-exclusive-variables}

+#### `cmakeEntries` {#cmake-entries}


Is there prior art in Nixpkgs that we can refer to here, such as for another build system?

AFAICT, this PR is the first one that implements structured flags attributes for a build system. The previous pattern is cmakeFlags and cmakeFlagsArray.

ttuegel · 2025-11-04T00:00:16Z

doc/hooks/cmake.section.md

+If `cmakeEntries[WITH_FOO]` is defined and `[[ cmakeEntryTypes[WITH_FOO] == BOOL ]]`,
+one can determine the condition with `[[ -n "${cmakeEntries[WITH_FOO]}" ]]`.
+When prepending to the flags, however, the value will become converted to either `ON` or `OFF`.


Do we have a motivating example in mind where we would use this in Bash?

Ah! This paragraph is for the previous attempt of this PR (where we have cmakeEntryTypes) and is no longer relevant.

In that design, Bash function can construct a conditional expression from a boolean cmakeEntries element using test -n or test -z, which is what we expect when passing a Nix derivation argument to the Bash builder:

if [[ -n "${cmakeEntries[ENABLE_FOO]}" ]]; then # Do something when using -DENBLE_FOO=ON else # Do something when using -DENBLE_FOO=OFF fi

In the current design, one simply assigns ON or OFF to "${cmakeEntries[ENABLE_FOO]}". { cmakeEntries.ENABLE_FOO = true; } is translated to cmakeEntries[ENABLE_FOO] when jq is available. However, we don't strongly enforce this policy, but provide tooling to accommodate other CMake-supported boolean values. For example. one can use testCMakeBool to construct a Bash conditional expression:

if testCmakeBool "${cmakeEntries[ENABLE_FOO]}"; then # Do something when using -DENBLE_FOO=ON else # Do something when using -DENBLE_FOO=OFF fi

testCMakeBool will fail with non-zero exit status.

I removed this paragraph.

ShamrockLee force-pushed the cmake-definitions branch 2 times, most recently from b124393 to 1717365 Compare September 11, 2025 15:54

ShamrockLee changed the title ~~cmake: setup-hooks: take structural cmakeDefinitions and cmakeDefinitionTypes~~ cmake: setup-hooks: take structural cmakeEntries and cmakeEntryTypes Sep 11, 2025

ShamrockLee force-pushed the cmake-definitions branch 4 times, most recently from aab158f to 183cc44 Compare September 11, 2025 18:05

ShamrockLee marked this pull request as ready for review September 11, 2025 18:05

nix-owners bot requested review from GetPsyched, LnL7, fricklerhandwerk, hsjobeki and ttuegel September 11, 2025 18:06

ShamrockLee force-pushed the cmake-definitions branch from 183cc44 to 5a8ce02 Compare September 11, 2025 18:25

nix-owners bot requested review from Mic92, martinetd, ragnard, ryan4yin and thoughtpolice September 11, 2025 19:41

nixpkgs-ci bot added the 2.status: merge conflict This PR has merge conflicts with the target branch label Sep 21, 2025

RossSmyth approved these changes Sep 28, 2025

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nixpkgs-ci bot added the 12.approvals: 1 This PR was reviewed and approved by one person. label Sep 28, 2025

LunNova mentioned this pull request Sep 29, 2025

llvmPackages: clean up rebuild avoidance #447071

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ShamrockLee force-pushed the cmake-definitions branch from ba34940 to ed8fbdf Compare November 3, 2025 11:13

ShamrockLee changed the title ~~cmake: setup-hooks: take structural cmakeEntries and cmakeEntryTypes~~ cmake: setup-hooks: take structural cmakeEntries Nov 3, 2025

ShamrockLee force-pushed the cmake-definitions branch 2 times, most recently from 4e6138f to c058a5b Compare November 3, 2025 11:19

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ShamrockLee added 2 commits November 3, 2025 19:21

cmake: setup-hook.sh: split parseShareDocName

7d8ee72

cmake: setup-hook.sh: preserve default assignment return status

618a9c6

ShamrockLee force-pushed the cmake-definitions branch from c058a5b to 9f57d2d Compare November 3, 2025 11:23

ShamrockLee force-pushed the cmake-definitions branch from 9f57d2d to 754b044 Compare November 3, 2025 11:27

nixpkgs-ci bot removed the 2.status: merge conflict This PR has merge conflicts with the target branch label Nov 3, 2025

ShamrockLee force-pushed the cmake-definitions branch from 754b044 to 182e3ab Compare November 3, 2025 11:38

ShamrockLee force-pushed the cmake-definitions branch from 182e3ab to dbd56f6 Compare November 3, 2025 20:14

ttuegel reviewed Nov 4, 2025

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cmake: setup-hooks: take cmakeEntries

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ShamrockLee force-pushed the cmake-definitions branch from dbd56f6 to f649401 Compare November 4, 2025 08:11

ShamrockLee added 3 commits November 4, 2025 16:49

cmake: throw when cmakeEntries contains null values

4b4b71a

cmake: propagate jq for non-minimal-build

d1586dc

libsolv: use structured attributes

aaa206d

ShamrockLee force-pushed the cmake-definitions branch from f649401 to 725c9c8 Compare November 4, 2025 08:50

libsolv: use cmakeEntries

7844ff4

ShamrockLee force-pushed the cmake-definitions branch from 725c9c8 to 7844ff4 Compare November 4, 2025 09:30

nixpkgs-ci bot added the 2.status: merge conflict This PR has merge conflicts with the target branch label Feb 1, 2026

		@@ -16,9 +16,35 @@ You can disable this hook’s behavior by setting `configurePhase` to a custom v

		### CMake Exclusive Variables {#cmake-exclusive-variables}

		#### `cmakeEntries` {#cmake-entries}

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