Add try_reserve/_exact methods for Vec?

fitzgen / bumpalo

A fast bump allocation arena for Rust

https://docs.rs/bumpalo

Apache License 2.0

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Add try_reserve/_exact methods for Vec? #66

Closed TheDan64 closed 4 years ago

TheDan64 commented 4 years ago

I tried to add these try_* methods (since I need fallible allocation) to Vec by wrapping the RawVec methods of the same names. However, they still seem to be infallible due to the alloc impl always returning Ok? https://github.com/fitzgen/bumpalo/blob/master/src/lib.rs#L1076

Would it be possible to make them fallible?

fitzgen commented 4 years ago

Thanks for opening an issue. I'm open to the idea, but I still have some design questions I'm unsure about:

Would you expect these methods to return an Err if the current chunk that we're bumping out of is full or only if the global allocator returns an error for getting a new chunk to bump out of?
A variant for each? I.e. try_alloc_in_current_chunk and try_alloc_in_new_chunk_if_necessary?

Finally, are you interested in doing the implementation work?

TheDan64 commented 4 years ago

Yeah, I'd be interested in implementation.

Personally, I'm only concerned about when the global allocator fails. However, if you think there's value in adding the other variant then we could do that too. Or at the very least keep the code open to adding that variant when someone does require it.

fitzgen commented 4 years ago

Ok, let's start with just the conservative approach of only when the global allocator fails :+1: