Reduce backref usage in split#6644
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headius merged 2 commits intojruby:jruby-9.2from Mar 31, 2021
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String#split appears to do nothing with the context backref slot except using it to receive the MatchData from a regexp match and eventually clearing it to nil. This patch sets up a thread-local IRubyObject[] holder to use for that out value and avoids using the context backref at all except for clearing it at the end. This fixes jruby#6160 by avoiding all reads of the context backref. It may still cause problems for other backref-reading functions that run concurrently and see the clearing to nil unexpectedly.
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There are likely other methods that claim to read or write backref but actually only use it as an extra return value from Regexp functions. |
See jruby#6640 for a failure that occurred in JRuby due to using the context backref slot as an "out" variable during regexp-based splitting.
This was referenced Mar 31, 2021
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String#split appears to do nothing with the context backref slot
except using it to receive the MatchData from a regexp match and
eventually clearing it to nil. This patch sets up a thread-local
IRubyObject[] holder to use for that out value and avoids using
the context backref at all except for clearing it at the end.
This fixes #6640 by avoiding all reads of the context backref. It
may still cause problems for other backref-reading functions that
run concurrently and see the clearing to nil unexpectedly.