regcomp.c: validate \g{...} contents past first number #23051
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This code used to silently accept \g{123trailing garbage} as long as it
started with a valid number.
Fixes Perl#23050.
khwilliamson
approved these changes
Mar 2, 2025
| @@ -220,6 +220,8 @@ my @death = | |||
| '/\g/' => 'Unterminated \g... pattern {#} m/\g{#}/', | |||
| '/\g{1/' => 'Unterminated \g{...} pattern {#} m/\g{1{#}/', | |||
| '/\g{-abc}/' => 'Group name must start with a non-digit word character {#} m/\g{-{#}abc}/', | |||
| '/\g{1-1}/' => 'Sequence \g{... not terminated {#} m/\g{1{#}-1}/', | |||
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To a human, it is obvious that this is terminated; just syntactically invalid. The parser can be forgiven for not being able to detect that. But it is unfortunate that the existing diagnostic doesn't give that as a possibility. You have to go to perldiag to find that a syntax error is a possibility, We likely can't change existing diagnostics, but this is a new error, and so a clearer error message could be devised.
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I was following the example of named backreferences:
$ perl -e '/\g{foo-bar}/'
Sequence \g{... not terminated in regex; marked by <-- HERE in m/\g{foo <-- HERE -bar}/ at -e line 1.
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That's understandable, and maybe it isn't for this PR, but I believe new warning instances shouldn't be bound by inadequacies in previous instances.
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This code used to silently accept
\g{123trailing garbage}as long as it started with a valid number.Fixes #23050.