fix(frankenphp): strip Go's -mthreads so the Windows build survives Clang >= 20

[m-this]

Retargeted onto fable-v3-windows and cut down to the one thing that branch is missing: the -mthreads fix. The linking fixes I originally had here are already on your branch (and more complete), so I dropped them.

Go passes the MinGW-only -mthreads flag to the C compiler for cgo builds (golang/go#16932), and the Clang on current windows-latest (VS 18 / LLVM 20+) rejects it for the MSVC target. So the final frankenphp go build fails there.

This wraps Clang with a generated .bat that drops the -mthreads token and forwards the rest (substring replace, so quoted paths survive). It only kicks in when the detected Clang refuses the flag, so older toolchains are untouched.

Verified on windows-latest: fable-v3-windows as-is fails at go build with unsupported option '-mthreads'; with this, frankenphp.exe builds and passes version and php-server.

Workflow used to build and smoke-test the binary

name: Check FrankenPHP Windows build

on:
  workflow_dispatch:
    inputs:
      version:
        description: php version
        default: '8.5'
        type: string
      extensions:
        description: extensions to compile (comma separated)
        default: 'bcmath,ctype,curl,dom,filter,fileinfo,iconv,mbstring,opcache,openssl,pdo,pdo_sqlite,phar,session,simplexml,sockets,sqlite3,tokenizer,xml,xmlreader,xmlwriter,zip,zlib'
        type: string
  push:
    paths:
      - src/Package/Target/php/frankenphp.php
      - .github/workflows/frankenphp-windows-check.yml

env:
  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  PHP_VER: ${{ inputs.version || '8.5' }}
  EXTS: ${{ inputs.extensions || 'bcmath,ctype,curl,dom,filter,fileinfo,iconv,mbstring,opcache,openssl,pdo,pdo_sqlite,phar,session,simplexml,sockets,sqlite3,tokenizer,xml,xmlreader,xmlwriter,zip,zlib' }}

jobs:
  build:
    name: frankenphp ${{ inputs.version || '8.5' }} on Windows x86_64
    runs-on: windows-latest
    timeout-minutes: 180
    steps:
      - uses: actions/checkout@v4
      - uses: shivammathur/setup-php@v2
        with:
          php-version: '8.4'
      - run: composer update --no-dev --classmap-authoritative
      # FrankenPHP requires Go >= 1.26; make sure the runner's older Go cannot shadow it
      - uses: actions/setup-go@v6
        with:
          go-version: stable
          cache: false
      - run: go version
      - run: ./bin/spc doctor --auto-fix
      - run: ./bin/spc download --with-php="$env:PHP_VER" --for-extensions="$env:EXTS" --for-libs=nghttp2 --ignore-cache-sources=php-src --retry 5
      - name: Build php-embed
        run: ./bin/spc build:php-embed --enable-zts "--with-libs=nghttp2,pthreads4w" "$env:EXTS"
      - name: Inspect php8embed.lib for zend_atomic_bool_store
        run: |
          $lib = Get-ChildItem -Recurse -Filter php8embed.lib | Select-Object -First 1
          Write-Host "lib: $($lib.FullName)"
          $dumpbin = (Get-ChildItem "C:/Program Files/Microsoft Visual Studio/*/*/VC/Tools/MSVC/*/bin/HostX64/x64/dumpbin.exe" | Select-Object -First 1).FullName
          & $dumpbin /SYMBOLS $lib.FullName | Select-String "zend_atomic_bool_store|InitSecurityInterface|PathCchCanonicalize" | Select-Object -First 20
      - name: Build frankenphp
        run: ./bin/spc build:frankenphp --enable-zts --with-libs=nghttp2 "$env:EXTS"
      - name: Smoke test binary
        run: |
          $bin = Get-ChildItem -Recurse -Filter frankenphp.exe | Select-Object -First 1
          & $bin.FullName version
          & $bin.FullName build-info
      - uses: actions/upload-artifact@v7
        if: always()
        with:
          name: frankenphp-windows-x86_64
          path: buildroot/bin/frankenphp.exe
          if-no-files-found: ignore
      - uses: actions/upload-artifact@v7
        if: failure()
        with:
          name: spc-logs
          path: log/

[henderkes]

This is most definitely not the right approach. I have a branch somewhere on v3 that successfully builds frankenphp on windows. If we have to create a wrapper around clang-cl it should be a simple inline bash script and not a program we need to compile.

https://github.com/crazywhalecc/static-php-cli/tree/fable-v3-windows

[m-this]

OK ! Thanks for your input, I will check on this branch

[m-this]

@henderkes I just changed the base branch to your fable-v3-windowsbranch, its much better, and I updated the PR description accordingly 😊

The .bat seems to be a good solution, for just stripping the -mthreads

[henderkes]

I still don't understand where exactly -mthreads is coming from and why it needs to be stripped. I was able to compile the linked branch without changes with VS26.

Is this a new go version? Or what's the cause here? If it's really go this almost certainly has to be raised with the Go team.

[m-this]

It's not a new Go version. Go has always added -mthreads when it calls the C compiler for cgo builds on Windows (see golang/go#16932, from 2016). What changed is clang: older versions just ignored the flag with a warning, but recent ones refuse it when targeting MSVC. Your local clang still accepts it, the one on windows-latest doesn't, which is why the build works for you but fails in CI.

Here it is on fable-v3-windows unmodified, failing at the go build step: https://github.com/m-this/static-php-cli/actions/runs/28867441688
Note it's runtime/cgo itself failing, Go's own package, before any FrankenPHP code compiles. Same workflow passing with this PR: https://github.com/m-this/static-php-cli/actions/runs/28867581250

Build log excerpt

github.com/caddyserver/caddy/v2/modules/standard
# runtime/cgo
clang: error: unsupported option '-mthreads' for target 'x86_64-pc-windows-msvc'
# runtime/cgo
clang: error: unsupported option '-mthreads' for target 'x86_64-pc-windows-msvc'
# runtime/cgo
clang: error: unsupported option '-mthreads' for target 'x86_64-pc-windows-msvc'

I agree this belongs upstream with Go, I can open an issue there. In the meantime the .bat wrapper only kicks in when clang rejects the flag, so your setup stays untouched 🙂

[m-this]

Opened the upstream issue with a standalone repro: golang/go#80290

[henderkes]

Ah clang 22, yeah, Go is the right place for this then. In the meantime we should merge it.

[henderkes]

We should add a comment linking to the Go issue so we can remove it later.

[m-this]

I just added a link and reference to it, good call !

[crazywhalecc]

Oh wait, this PR is merged into fable-v3-windows branch...

[henderkes]

Yes, that contains a bunch of other fixes necessary to make (franken)php build on windows