On 12/10/2013 3:28 AM, Chris Pearce wrote:
Hi All,
Can we start using C++ STL containers like std::set, std::map,
std::queue in Mozilla code please? Many of the STL containers are more
convenient to use than our equivalents, and more familiar to new
contributors.
I understand that we used to have a policy of not using STL in mozilla
code since some older compilers we wanted to support didn't have very
good support, but I'd assume that that argument no longer holds since
already build and ship a bunch of third party code that uses std
containers (angle, webrtc, chromium IPC, crashreporter), and the sky
hasn't fallen.
The sizeOfExcludingThis/sizeOfIncludingThis methods on our containers
are one feature not found in STL. There are some codesize concerns in
using STL, as it is much more template-heavy than our own
implementations (particularly in regards to
std::unordered_map/nsTHashtable). The final issue is that performance
characteristics may be very different: C++11 disallows copy-on-write
semantics for std::string, for example; in another edge case, most STL
containers' move constructors require noexcept semantics to become
enabled (and autodegrades move to copy in most cases), and I'm not
certain that compiling without exception support would grant us those
semantics.
Also, std::set and std::map are the wrong containers to use 95% of the
time. If people don't want to use nsTHashtable because the API sucks,
it's better to change the API for nsTHashtable rather than use the wrong
datatype.
I think the right answer is to make the myriad of datatypes we have more
STL-ish--as a first step at least, can we at least add iterator support
for them and get rid of the abominable
EnumerateForwards/EnumerateBackewards methods? This would allow us to
use range-based for once our minimum compiler support gets there.
--
Joshua Cranmer
Thunderbird and DXR developer
Source code archæologist
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