Skip the make jobserver on Windows#9630
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The POSIX make jobserver passes tokens through an inherited pipe identified by file descriptor numbers, which Windows cannot inherit, and nmake aborts every native extension build with `fatal error U1065: invalid option '-'` when it finds the GNU make `--jobserver-auth` left in MAKEFLAGS. Skip the jobserver entirely on Windows so bundle install keeps working with nmake. https://github.com/ruby/rbs/actions/runs/27736519019/job/82054372031 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The example exercises the genuine Windows code path, so tag it `windows_only` and exclude it elsewhere instead of stubbing `Gem.win_platform?`. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The first version skipped the jobserver on every Windows platform, but mingw uses GNU make and consumes the jobserver tokens through the inherited pipe without trouble. Only nmake on mswin reads MAKEFLAGS as bare option letters and rejects the GNU make `--jobserver-auth`. Detect nmake the way the extension builder does and skip the jobserver only then, so mingw keeps building in parallel. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This was referenced Jun 23, 2026
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Since the make jobserver was introduced, bundle install fails on mswin for every gem with native extensions. The parallel installer adds a GNU make
--jobserver-authto MAKEFLAGS, which nmake inherits and reads as bare option letters. nmake then aborts each build withfatal error U1065: invalid option '-'. This broke ruby/rbs CI while installing bigdecimal, prism, digest, ffi and others.https://github.com/ruby/rbs/actions/runs/27736519019/job/82054372031
mingw and other Windows toolchains use GNU make and consume the jobserver tokens through the inherited pipe without trouble, so the skip is limited to nmake. The make program is detected the same way the extension builder picks it, honoring the MAKE environment variable and the mswin default.
The added spec forces nmake through the MAKE environment variable and checks that MAKEFLAGS is left untouched.