protocolbuffers/protobuf

Protobuf library requires bash.exe / WSL, seemingly unnecessarily

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#27307 opened on May 9, 2026

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bughelp wanted

Description

What version of protobuf and what language are you using?

Version: 35.0-rc2 (from BCR)

Language: C++

What supported operating system version are you using (e.g. Linux, Windows) ? Windows 11

What supported runtime / compiler version are you using (e.g. python version, gcc version) MSVC

What did you do? Attempt to build a protobuf target dependency on Windows 11.

Steps to reproduce the behavior:

  1. On a Windows 11 fresh install, no WSL, no bash.exe
  2. Use Bazel and write a Protobuf target. In my specific case I installed opentelemetry-proto and tried to build a target which has dependency on metrics_proto here: https://github.com/bazelbuild/bazel-central-registry/blob/main/modules/opentelemetry-proto/1.8.0/overlay/BUILD.bazel
  3. Observe build failure

What did you expect to see Successful build of a cc_proto_library() target

What did you see instead?

ERROR: C:/users/stepa/_bazel_stepa/hr2rqvqb/external/protobuf+/bazel/private/oss/toolchains/prebuilt/BUILD.bazel:25:20: ProtocAuthenticityCheck external/protobuf+/bazel/private/oss/toolchains/prebuilt/validation_output.txt failed: (Exit 1): bash.exe failed: error executing ProtocAuthenticityCheck command (from protoc_authenticity rule target @@protobuf+//bazel/private/oss/toolchains/prebuilt:authenticity_validation) C:\Users\stepa\AppData\Local\Microsoft\WindowsApps\bash.exe -c ... (remaining 1 argument skipped)
Windows Subsystem for Linux has no installed distributions.
You can resolve this by installing a distribution with the instructions below:

Use 'wsl.exe --list --online' to list available distributions
and 'wsl.exe --install <Distro>' to install.

I believe this is a repeat of https://github.com/protocolbuffers/protobuf/issues/19408. The problem seems to stem from https://github.com/protocolbuffers/protobuf/blob/main/bazel/private/oss/toolchains/prebuilt/protoc_authenticity.bzl#L18

It looks like this was attempted to be resolved in https://github.com/protocolbuffers/protobuf/pull/19409 but there's a regression.

Contributor guide

Tech stack
cpp
Domain
build systemdevops
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
knowledge of Bazel build systemWindows environment
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Investigate the bazel/private/oss/toolchains/prebuilt/protoc authenticity.bzl file, specifically the line that invokes bash.exe. Examine the previous PR #19409 that attempted to fix this issue and see if the regression was introduced there. Check if there is a way to make the authenticity check work without requiring bash.exe, possibly by using a native Windows tool or a cross platform approach. The build error occurs during the ProtocAuthenticityCheck rule, so understanding that rule and its dependencies is key.