Bug #22381: MatchData assigned to $~ is incorrectly reused

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.3: DONTNEED, 3.4: DONTNEED, 4.0: REQUIRED

[jhawthorn (John Hawthorn)]

m = /a/.match("a").dup # dup a MatchData (has no "busy" flag set)
$~ = m # assign to $~
/b/ =~ "b" # perform a match that sets $~
p m
# "b" on Ruby 4.0 (and 1.8-2.7, incorrect)
# "a" on Ruby 3.0-3.4 (correct)

This is because the MATCH_BUSY flag isn't set correct and so the implicit match reuse (removed in #17507, re-added in #20652) mutates this escaped value

[jhawthorn (John Hawthorn)]

• Description updated (diff)

[jhawthorn (John Hawthorn)]

• Backport changed from 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN to 3.3: DONTNEED, 3.4: DONTNEED, 4.0: REQUIRED