Issue #21286 has been updated by MSP-Greg (Greg L). I just updated the code in https://github.com/ruby/setup-msys2-gcc (the repo that assembles Windows build tool archive files), it is now downgrading to gcc 14. I think this should fix the issue. I checked with Puma (extension gem), as it was affected. At some point, I assume we'll be able to re-enable gcc-15 for a limited set of Ruby versions. Lastly, I added `-std=gnu17` to `CFLAGS` (as per the above 'Porting to GCC 15'), and Ruby master built locally. ---------------------------------------- Bug #21286: Windows - MSYS2 just updated to GCC 15.1.0, builds failing https://bugs.ruby-lang.org/issues/21286#change-112814 * Author: MSP-Greg (Greg L) * Status: Open * ruby -v: master * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- MSYS2 just updated to GCC 15.1.0, and the ruby-loco builds failed to compile. See [MinGW](https://github.com/MSP-Greg/ruby-loco/actions/runs/14693708990/job/412325097...) & [UCRT](https://github.com/MSP-Greg/ruby-loco/actions/runs/14693775816/job/412326620...) Also, I compiled mswin locally with the recent VS 'preview' release, and the bug has been fixed. -- https://bugs.ruby-lang.org/