[Bug 1864364] Re: Possible Regession: PCRE2 fails to match regex

[Stuart Auchterlonie]

This is affecting the Beta of Impish Indri (21.10)

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Title:
  Possible Regession: PCRE2 fails to match regex

Status in pcre2 package in Ubuntu:
  Confirmed

Bug description:
  I am reporting this bug in response to a discussion in [gnome-
  terminal][1]. It looks like there has possibly been a regression from
  EOAN to FOCAL in pcre2.

  Given the following regex:

      <code>(?<APOS_START>(?<='))?" "(?(DEFINE)(?<S4>(?x: (?: [0-9] |
  [1-9][0-9] | 1[0-9]{2} | 2[0-4][0-9] | 25[0-5] ) (?! [0-9] ) )))"
  "(?(DEFINE)(?<IPV4>(?x: (?: (?&S4) \\. ){3} (?&S4) )))"
  "(?(DEFINE)(?<S6>[[:xdigit:]]{1,4})(?<CS6>:(?&S6))(?<S6C>(?&S6):))"
  "(?(DEFINE)(?<IPV6>(?x: (?: " "(?x: :: )" " | " "(?x: : (?&CS6){1,7}
  )" " | " "(?x: (?! (?: [[:xdigit:]]*: ){8} ) (?&S6C){1,6} (?&CS6){1,6}
  )" " | " "(?x: (?&S6C){1,7} : )" " | " "(?x: (?&S6C){7} (?&S6) )" " |
  (?: " "(?x: (?&S6C){6} )" " | " "(?x: :: (?&S6C){0,5} )" " | " "(?x:
  (?! (?: [[:xdigit:]]*: ){7} ) (?&S6C){1,4} (?&CS6){1,4} ) :" " | "
  "(?x: (?&S6C){1,5} : )" " ) (?&IPV4) ) (?! [.:[:xdigit:]] ) )))"
  "(?(DEFINE)(?<PATH_INNER>(?x: (?: "
  "[-[:alnum:]\\Q_$.+!*,:;@&=?/~#|%'\\E]" "* (?: \\( (?&PATH_INNER) \\)
  | \\[ (?&PATH_INNER) \\] ) )* "
  "[-[:alnum:]\\Q_$.+!*,:;@&=?/~#|%'\\E]" "* )))"
  "(?(DEFINE)(?<PATH>(?x: (?: " "[-[:alnum:]\\Q_$.+!*,:;@&=?/~#|%'\\E]"
  "* (?: \\( (?&PATH_INNER) \\) | \\[ (?&PATH_INNER) \\] ) )* (?: "
  "[-[:alnum:]\\Q_$.+!*,:;@&=?/~#|%'\\E]" "* (?(<APOS_START>)"
  "[-[:alnum:]\\Q_$+*:@&=/~#|%\\E]" "|"
  "[-[:alnum:]\\Q_$+*:@&=/~#|%'\\E]" ") )? )))" "(?<!(?:" "(?x:
  [-[:alnum:]] | (?! [[:ascii:]] ) [[:graph:]] )"
  "|[.]))(?=(?i:www|ftp))" "(?x: (?: " "(?x: [-[:alnum:]] | (?!
  [[:ascii:]] ) [[:graph:]] )" "+ \\. )* " "(?x: [-[:alnum:]] | (?!
  [[:ascii:]] ) [[:graph:]] )" "* (?! [0-9] ) " "(?x: [-[:alnum:]] | (?!
  [[:ascii:]] ) [[:graph:]] )" "+ )" "(?x: \\:" "(?x: (?:
  [1-9][0-9]{0,3} | [1-5][0-9]{4} | 6[0-4][0-9]{3} | 65[0-4][0-9]{2} |
  655[0-2][0-9] | 6553[0-5] ) (?! [0-9] ) )" " )?" "(?x: /(?&PATH)
  )?</code>

  And the following input:

      www.foo.bar/baz
      WWW3.foo.bar/baz
      FTP.FOO.BAR/BAZ
      ftpxy.foo.bar/baz

  The regex should match but does actually not match.

  In EOAN this still worked as I have just confirmed in a virtual
  machine.

  [1]: https://gitlab.gnome.org/GNOME/gnome-terminal/issues/221

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: libpcre2-8-0 10.34-7
  ProcVersionSignature: Ubuntu 5.4.0-14.17-generic 5.4.18
  Uname: Linux 5.4.0-14-generic x86_64
  ApportVersion: 2.20.11-0ubuntu17
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Sun Feb 23 15:49:32 2020
  InstallationDate: Installed on 2020-02-04 (18 days ago)
  InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
  SourcePackage: pcre2
  UpgradeStatus: Upgraded to focal on 2020-02-22 (0 days ago)

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