Re: (require 'cus-load) clobbers match-data

[Davis Herring]

> In general, there should be no expectation that any operation in Emacs
> will preserve the match-data (unless it explicitly says so).
>
>> Maybe require should save and restore the match data itself?
>
> This would be completely unnecessary in the vast majority of cases.
> Since a require can run arbitrary code, there should be no expectation
> that it preserves match-data.

This may not have been the original point, but loading a library can be
the result of calling an autoloaded function, even one that advertises
that it preserves the match data.  In that case it makes sense for `load'
(or something else in that sequence) to save it; loading a file is
(typically) already expensive compared to `save-match-data'.

Davis

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