[ruby-core:112453] [Ruby master Bug#19442] Remove USE_RINCGC flag

Issue #19442 has been updated by peterzhu2118 (Peter Zhu). I'm for removing many of the untested code paths in gc.c since they may be buggy and are probably not used (like this one, which doesn't even compile so clearly nobody is using it). ---------------------------------------- Bug #19442: Remove USE_RINCGC flag https://bugs.ruby-lang.org/issues/19442#change-101897 * Author: eightbitraptor (Matthew Valentine-House) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- [GitHub PR #7317](https://github.com/ruby/ruby/pull/7313) Ruby doesn't compile when USE_RINCGC is disabled. It's also not being tested in CI. As @nobu has pointed out in comments on the PR, fixing it is simple. I think there are 2 approaches we could take: 1. Remove `USE_RINCGC` entirely and always run with incremental GC enabled. We have a precedent for this: `USE_RGENGC=0` was removed [in this commit](https://github.com/ruby/ruby/commit/62c2b8c74e47652fc5bbaf6150f4acd… almost 3 years ago. `USE_RINCGC=0` is in a similar state. It has been broken for almost a year (since [this commit](https://github.com/ruby/ruby/commit/dde164e968e382d50b07ad455946888…), and [disabled in CI for more than 2 years](https://github.com/ruby/ruby/commit/46d3ea2c2569e2e5a9ee3e7e206f07f0…. 2. We could fix `USE_RINCGC`. If we do this we should re-enable the CI task so that we continue to keep it working in the future. I am very much in favour of option 1, because I don't think this flag is being actively used, and removing it will simplify the code and reduce the cognitive overhead of working with the GC. However I am happy to defer to the team here. -- https://bugs.ruby-lang.org/