[ruby-core:103357] Re: [Ruby master Feature#17790] Have a way to clear a String without resetting its capacity

[e-mail] wrote:
> > so providing a capacity method gives more control over how to expand memory 
> 
> Agreed. Without also exposing the capacity, my proposed change would be a big footgun. 

Yes, rb_str_resize(str, 0) is common to workaround the lack of
escape analysis inside the core VM and some C exts.  I think
it's reasonable for Rubyists to use String#clear for the same
purpose.

> Maybe `String#capacity` and `String#capacity=` would make sense? But then there's the question of the behavior if you set the capacity to lower than the `size`. Should it truncate? (this could corrupt UTF-8 for instance) or should it raise?

Yes, but I don't know what it should do for corruption.  It
would also be useful for IO#read-like methods if/when that
supports destination buffer offsets.

> Additionally I think `Array` and `Hash` should expose similar ways of querying and reserving capacity.

Probably, yes.  It seems a bit low-level, but I've been favoring
"semi-automatic" memory management since we probably can't have
escape analysis due to the C API.

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