1232327 - Figure out a way to make JS vector usage require explicitly-selected AllocPolicy for heap-allocated vectors

Status: NEW

(Core :: JavaScript Engine, enhancement, P5)

Description

[Jeff Walden [:Waldo]]

It's quite often a mistake to have js::Vector<T> or js::Vector<T, N> in heap-allocated classes -- in fact it's almost always (always?) an error.  We should forbid this somehow.

I don't know if clang exposes enough rope for this on template aliases.  But if we could tag template aliases MOZ_STACK_CLASS or MOZ_HEAP_CLASS, we could tag js::Vector as MOZ_STACK_CLASS and fork out js::HeapVector (with the AllocPolicy argument mandatory) for use on the heap and be good.  If we can't do that immediately, perhaps we could add sufficient clang-plugin support to do it.

Comment 1

[Nicolas B. Pierron [:nbp]]

I am not sure to understand why this is a mistake, if <N represents the most frequent use cases, while still having support for >>>N cases.