join: be less magical and handle magic with less undefined behaviour #21502
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This code had a few problems: - changes to the content of delim from set or overload magic could result in the separator between elements changing during the process of the join. - changes to the content of delim which allocated a new PVX resulted in access to freed memory - changes to the flags of delim, the UTF-8 flag in particular, could result in an invalid joined string, either mojibake or an invalidly encoded upgraded string To avoid that, we copy the separator, either into a local buffer if it's large enough, or an allocated buffer, and save the flag we use, to prevent changes to the delim SV from changing or invalidating the delimpv value. Fixes Perl#21458 and some similar problems.
No tests since I don't have the memory.
leonerd
reviewed
Sep 25, 2023
leonerd
reviewed
Sep 25, 2023
I changed $n to 2 in each case as a defence against a reasonable possible optimisation of $x x 1 sharing the PV with $x.
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Fixes #21458
Also fixed a couple of other minor problems.