[jira] [Commented] (DAFFODIL-412) asserts and discriminators with testKind pattern should have warning on too-long match

["Larry Barber (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DAFFODIL-412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17237752#comment-17237752 ] 

Larry Barber commented on DAFFODIL-412:
---------------------------------------

Would it even make sense for something with this type of variable length pattern search to be part of a parent element with a specified length? 

> asserts and discriminators with testKind pattern should have warning on too-long match
> --------------------------------------------------------------------------------------
>
>                 Key: DAFFODIL-412
>                 URL: https://issues.apache.org/jira/browse/DAFFODIL-412
>             Project: Daffodil
>          Issue Type: Improvement
>          Components: Back End, Diagnostics, Front End, Usability
>    Affects Versions: s5
>            Reporter: Mike Beckerle
>            Priority: Major
>
> When an assert/discriminator is of testKind pattern the pattern test passes if the regex matches a prefix of the data stream at the start of the element 
> This match attempt is not bounded by the length of the element.
> It's entirely possible for a very bad regex pattern to cause massive scanning of the data stream before returning a match or a failure.
> Our runtime should emit warnings if this is happening i.e., an attempt to match a regex that consumes more than N characters should emit a warning, then every N more characters, etc.
> A tunable limit should be created for this regex lookahead/match so that we can force a failure here. The Daffodil API should provide a way to set this tunable limit.



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