Bug #21291: possible bug with /m regexp and $ based on input

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: 3.4.2
• Backport: 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED

[zenspider (Ryan Davis)]

reported in discord by the.unnamed user:

#!/usr/bin/env -S ruby -vw
# => ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [arm64-darwin24]

p "a\n" =~ /$./m
# => 1
p "a\n" =~ /$.*/m
# => 1
p "aa\n" =~ /$./m
# => 2
p "aa\n" =~ /$.*/m       # !!!
# => nil
p "aa\n" =~ /$[\S\s]*/m
# => 2

goes back to at least 3.2.8

[nobu (Nobuyoshi Nakada)]

1.8 prints 2 but 1.9 and later print nil.

[nobu (Nobuyoshi Nakada)]

• Backport changed from 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN to 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED

[dodecadaniel (Daniel Colson)]

Possible fix: https://github.com/ruby/ruby/pull/13200