bug#67696: 30.0.50; Help deal with multiple versions in load-path

[Stefan Kangas]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Another option is to tweak `require` directly: the new function works
> basically "identically" to `require` expect for the added checks.
[...]
> But yes, we could change `require` to behave more like
> `require-with-check`.  The downside is that it's more risky, and it may
> come with a performance cost (it means that calling `require` repeatedly
> isn't as cheap as `(memq F features)`).

Right.  On the other hand, perhaps hitting the file system is to some
extent expected once you start asking for libraries to be loaded.  You
only get the best case `(memq F features)' if that evaluates to `t'.

Personally, I don't have a good view of how common these problems are.
Perhaps they are relatively uncommon, and it's too much to ask all users
of `require' to pay a cost for added correctness in unusual cases.