`_const_cast` is de facto undefined behavior

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
c, r
Domain
data

Research direction

Start by reviewing src/fread.c at lines 126-133 and the surrounding fread implementation. Confirm whether _const_cast invokes undefined behavior as described, then investigate a defined alternative for the copy-on-write behavior; done means a technically agreed solution is identified.

Written by the indexing model from the issue text.

Description

internals

https://github.com/Rdatatable/data.table/blob/9c54bd073decac61dbd284c7a22d65d0f719aa19/src/fread.c#L126-L133

I am aware that the usage of sidestepping constness is used to invoke copy on write behavior.

This is still undefined behavior.

I'm going to investigate to see if I can find a decent solution to this problem, and I also want to hear back if anyone disagrees with my assessment.

Dominant language
R
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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