Allow platform-specific startup bazelrc flags by keith · Pull Request #26882 · bazelbuild/bazel

keith · 2025-09-03T01:17:19Z

This enables the use of startup:linux, startup:macos, etc. This is
always enabled.

RELNOTES[inc]: Add support for startup:linux, startup:macos, etc
bazelrc options.

gregestren

Idea LGTM. I'd update the docs to acknowledge startup support too (maybe just acknowledge on the https://bazel.build/run/bazelrc#enable_platform_specific_config).

And this one isn't triggered by the flag?

gregestren · 2025-09-18T16:54:42Z

          && !command.equals(ALWAYS_PSEUDO_COMMAND)
-          && !command.equals(COMMON_PSEUDO_COMMAND)) {
+          && !command.equals(COMMON_PSEUDO_COMMAND)
+          && !command.equals(STARTUP_PSEUDO_COMMAND)) {


What makes this necessary now if startup was already a known key?

Naively, couldn't the C++ code remove the arch-specific suffix so at this point Bazel sees the same generic startup setting it would see for any other it already processes?

validCommands here is the literal subcommands like build, test etc, so it doesn't include startup. Without this addition this logic prints:

WARNING: while reading option defaults file '/private/tmp/foo/.bazelrc': invalid command name 'startup:linux'.

Naively, couldn't the C++ code remove the arch-specific suffix so at this point Bazel sees the same generic startup setting it would see for any other it already processes?

I think that would work, but I don't know of any downsides with this change either. I could imagine that version being worse for --announce_rc output but currently that doesn't show any difference AFAICT

validCommands here is the literal subcommands like build, test etc, so it doesn't include startup

That makes sense. But why wasn't this an issue before with existing startup: --foo settings? I think somehow those are stripped out before they get to this point, but startup:linux isn't?

I think that would work, but I don't know of any downsides with this change either.

If that works, IMO it's a bit nicer in that it's a more isolated change. Just change a single function in the .cc file and no changes needed for this file?

I could imagine that version being worse for --announce_rc output but currently that doesn't show any difference AFAICT

If that's less accurate, that's a fair critique. What specifically might it say inaccurately? You didn't actually notice that happening?

To be clear, I'm not super-familiar with the C++ options parsing. These questions are mostly me trying to clarify my basic understanding of the surrounding code.

ok my understanding of this has changed reading more.

before this change this logic would warn if you have something like startup:foo in your .bazelrc, since that was always invalid, with this change, that warning never appears (although we could keep it as long as we manually filtered out the known valid platform based ones)

but the C++ logic and this java parsing logic are entirely separate. they both parse the bazelrc separately, so I think we have to have changes in both places. the C++ logic doesn't forward it post-parse, it just applies the settings and drops its knowledge of things AFAICT.

keith · 2025-09-20T04:16:55Z

docs updated!

And this one isn't triggered by the flag?

correct. my thought was it wasn't worth gating since this couldn't have had previously functioning configs to conflict with (I think startup:foo --bar might have been accepted but never would have done anything).

I'm also hoping that in the future we can remove --enable_platform_specific_config, like an incompatible flag, if no major issues come up from having flipped the default so I didn't want to put more functionality behind it.

This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes #22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options.

meisterT · 2025-10-16T14:04:58Z

@gregestren is this good to be merged?

keith · 2026-03-13T19:51:26Z

@gregestren friendly ping

fmeum · 2026-04-04T07:12:06Z

@bazel-io fork 9.1.0

This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes bazelbuild#22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options. Closes bazelbuild#26882. PiperOrigin-RevId: 896083689 Change-Id: Id4da6e6689e337951664317755596cfd4ab52703

….com/baz… (#29251) …elbuild/bazel/pull/26882) This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes #22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options. Closes #26882. PiperOrigin-RevId: 896083689 Change-Id: Id4da6e6689e337951664317755596cfd4ab52703  ### Description  ### Motivation  ### Build API Changes  No ### Checklist - [ ] I have added tests for the new use cases (if any). - [ ] I have updated the documentation (if applicable). ### Release Notes  RELNOTES: None Commit ea7b4ba Co-authored-by: Keith Smiley <[email protected]>

….com/baz… (bazelbuild#29251) …elbuild/bazel/pull/26882) This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes bazelbuild#22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options. Closes bazelbuild#26882. PiperOrigin-RevId: 896083689 Change-Id: Id4da6e6689e337951664317755596cfd4ab52703  ### Description  ### Motivation  ### Build API Changes  No ### Checklist - [ ] I have added tests for the new use cases (if any). - [ ] I have updated the documentation (if applicable). ### Release Notes  RELNOTES: None Commit bazelbuild@ea7b4ba Co-authored-by: Keith Smiley <[email protected]>

This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes #22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options. Closes #26882. PiperOrigin-RevId: 896083689 Change-Id: Id4da6e6689e337951664317755596cfd4ab52703  ### Description  ### Motivation  ### Build API Changes  No ### Checklist - [ ] I have added tests for the new use cases (if any). - [ ] I have updated the documentation (if applicable). ### Release Notes  RELNOTES: None Commit ea7b4ba Co-authored-by: Keith Smiley <[email protected]>

keith mentioned this pull request Sep 3, 2025

Allow platform-specific startup options #22763

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keith marked this pull request as ready for review September 3, 2025 15:51

github-actions Bot added team-Rules-CPP Issues for C++ rules awaiting-review PR is awaiting review from an assigned reviewer labels Sep 3, 2025

meisterT requested a review from gregestren September 11, 2025 10:16

meisterT added team-Configurability platforms, toolchains, cquery, select(), config transitions and removed team-Rules-CPP Issues for C++ rules labels Sep 11, 2025

gregestren reviewed Sep 18, 2025

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keith force-pushed the ks/allow-platform-specific-startup-bazelrc-flags branch from d962ff2 to 35d5d85 Compare September 20, 2025 04:15

keith requested a review from fweikert as a code owner September 20, 2025 04:15

Allow platform-specific startup bazelrc flags

d5945de

This enables the use of `startup:linux`, `startup:macos`, etc. This is always enabled. Fixes #22763 RELNOTES[inc]: Add support for `startup:linux`, `startup:macos`, etc bazelrc options.

keith force-pushed the ks/allow-platform-specific-startup-bazelrc-flags branch from 35d5d85 to d5945de Compare September 22, 2025 18:14

gregestren approved these changes Apr 3, 2026

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gregestren added awaiting-PR-merge PR has been approved by a reviewer and is ready to be merge internally and removed awaiting-review PR is awaiting review from an assigned reviewer labels Apr 3, 2026

bazel-io mentioned this pull request Apr 4, 2026

[9.0.2] Allow platform-specific startup bazelrc flags #29228

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copybara-service Bot closed this in ea7b4ba Apr 7, 2026

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iancha1992 mentioned this pull request Apr 8, 2026

[9.0.2] Allow platform-specific startup bazelrc flags (https://github.com/baz… #29251

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iancha1992 mentioned this pull request Apr 9, 2026

[9.1.0] Allow platform-specific startup bazelrc flags #29262

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