On 5/25/12, Paweł Sikora <pl...@agmk.net> wrote: > On Friday 25 of May 2012 10:15:54 Diego Novillo wrote: > > Lawrence, Ian and Gaby have been working on the proposed coding > > guidelines for C++ (http://gcc.gnu.org/wiki/CppConventions). > > on this page we can read: > > "The following features of the C++ language should in general > be avoided in GCC code. (...) Defining new templates (use of > existing templates, e.g., from the standard library, is fine)."
That rule came from Ian's approach with gold. It works well for a new project. It does not work well in gcc. > so, why you just don't use the hash table implementation from > libstdc++? Diego and I looked long and hard at this issue. It all came down to a sequence of problems. First, libstdc++ isn't rigged for GTY, so we would have to instrument the library. Second, the GTY parser doesn't handle C++, so we would have to redo the GTY parser. Third, PCH requires gc, which requires GTY, so we cannot easily get rid of gc. Fourth, any use of libstdc++ will make different tradeoffs in size and performance, so any switch would require both a change in form and a change in substance. We would simultaneously have to show benefit on two axes, which is a predictor of trouble. So, instead we chose to take a more incremental approach, exploiting C++ with the existing algorithms and requiring mostly mechanical changes in client code. Both the hash table and vector patches take that approach. -- Lawrence Crowl
