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Re: Backporting ac3afc4b35 (regcomp.c: make \K+ and \K* illegal.)

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Ricardo Signes
February 8, 2020 21:38
Re: Backporting ac3afc4b35 (regcomp.c: make \K+ and \K* illegal.)
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On Fri, Feb 7, 2020, at 1:08 PM, Steve Hay via perl5-porters wrote:
> Unless there is some overriding (security-based) need to have it then I think we should not, at least in its current form.
> If it really is an essential fix to include then is there some way to rework it that retains the fix itself but without introducing the new error?


 The following types of change are NOT acceptable:
 * Patches that add new warnings or errors or deprecate features.

I think it would be a mistake to introduce a new error unless there is a grave, pressing reason. A large part of the purpose of the strictness of maintenance releases is to make upgrading within one version of perl5 as close to guaranteed safe as possible. Security and crashing fixes are eliminated, no other behavior is changed. Introducing a new fatal error is a loaded gun.

This will not affect only programs that would already be broken.

$ perl5.30.1 -E 'if (0) { /\K+/ } say "ok 1"'
ok 1

~/code/perl5$ ./perl -I lib -E 'if (0) { /\K+/ }'
\K+ is forbidden - matches null string many times in regex; marked by <-- HERE in m/\K+ <-- HERE / at -e line 1.

-1 on applying this to maint.

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