On Thu, Jul 03, 2014 at 07:52:59PM +0200, Tobias Grosser wrote: > On 03/07/2014 19:23, Roman Gareev wrote: > >Dear gcc contributors, > > > >could you please answer a few questions about std::map? Does gcc have > >a policy that forbids using of map in the source code of gcc? Can this > >using create a new installation dependency, which requires libstdc++? > >I would be very grateful for your comments. > > https://gcc.gnu.org/codingconventions.html#Standard_Library > > This suggests that using std::map is allowed. Running "grep 'std::' *" > on gcc, we only find a couple of std::make_pair, std::min and std::max > calls, but I don't see why we should not use std::map. I would say go for it > if there are no vetos. It seems to be the right tool for what you are aiming > for and certainly makes the code a lot more readable.
I'm certainly not opposed to using the stl when it makes sense, and reinventing our own stl has a fairly high cost. However I think the question of if you should use std::map is a complicated one. First remember std::map is a tree, not a hash table, and consider which performance characteristic you want. Also remember the stl in some cases trades off possible optimizations to be more generic, if you implement your own version of something you can say ban arrays larger than 2^32 and thereby save a bit of space. When you use the stl you also need to make sure you don't call things that can throw exceptions since gcc is built with -fno-exceptions and generally isn't exception safe. I think there are some stl things you should basically always prefer e.g. std::swap, there are some things you should think about before using, and some things that are best avoided. Personally I think you should favor hash tables to std::map most of the time because of there generally better performance. btw if you have specific gripes about the stlish bits gcc already has I'd like to hear them. Trev > > Cheers, > Tobias
