948538 - Add STL iterator support to XPCOM datatypes

Status: NEW

(Core :: XPCOM, defect)

Description

[Joshua Cranmer [:jcranmer]]

For better or worse, the STL and C++ libraries are built around iterator concepts. Adding iterators to our ADTs would allow us to use <algorithm> helpers if we so chose (there might be codesize concerns with std::sort, but the std::lower_bound/std::push_heap, etc.-equivalent functions in nsTArray all appear to be templated anyways, so we'd probably lose no codesize there). Also, iterators would allow us to use range-based for when our min requirements are >MSVC 2013 and >gcc 4.6.

One concern bsmedberg brought up over IRC is whether or not iterators should be mutation-safe. C++11's rules for iterator safety on std::vector basically boil down to "if the pointer in the iterator would no longer point to the correct thing, it's invalid." We can make iteration be mutation-safe by an extra level of indirection, but given that STL generally isn't mutation-safe, it may be more advantageous just to have debug-only assertions if you try to use an invalidated iterator.

Thoughts?

Comment 1

[(no longer active)]

I think debug only assertions are fine.  We should not try to provide a strong guarantee than the STL provides for the sake of compatibility with its API.

Comment 2

[Nathan Froyd [:froydnj]]

Debug only assertions sound fine to me.