Fix leak, broken collation of UTF-8 string in non-UTF8 locale #22963
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We no longer need to have declarations first thing in a block. This allows removing a block and outdenting. And it outdents further in preparation for a later commit Also adds/clarifies some comments
The minimal space potentially freed up by this isn't worth the extra libc call needed to accomplish it.
This function has a successful return branch and an unsuccessful return branch, and a macro common to both, named CLEANUP_STRXFRM. There is another code clause repeated in both branches. This reorders some of the statements in each branch so that that clause is positioned to just after the calls to CLEANUP_STRXFRM. The next commit will add it to the macro, so as to remove the redundant code clause.
This refactors a few clauses so that the case of having a UTF-8 string in a UTF-8 locale can potentially be handled as a distinct situation. This prepares for a potential future change to deal with above-Unicode code points, which strxfrm() vary well may not deal with properly.
This uses the new function forms for doing this translation that can avoid unnecessary mallocs
This commit creates a new variable, sans_highs, to store newly allocated memory that only happens sometimes. Just before returning, that is freed. This is the final step in solving the leak spotted by Tony Cook in https://github.com/Perl/perl5/pulls?q=sort:updated-desc%20is:pr%20is:closed#discussion_r1868633416 The problem was that there were potentially 0 to 3 mallocs in this function, and it was only freeing up to two of them. The solution is to have a separate variable for each malloc, and to free them all before returning. If the corresponding malloc did not happen, the variable will be NULL, and no free will occur. This makes a loop rather more complicated. The next commit will simplify it.
This loop has gotten rather complicated. This refactors it to simplify it. It uses the typical paradigm used elsewhere in the code of having a while loop with a source pointer, and a dest pointer, and copying and incrementing them independently as needed as we go along.
We were creating a string but failed to set its length; hence the one from the old string was used.
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This supercedes #22811
It started out just trying to convert to using the new forms for converting between bytes and UTF-8, but more problems were found.