Am Wed, 11 Nov 2015 13:08:06 +0000 schrieb David Nadlinger <[email protected]>:
> Hi all, > > Kenji and Walter have been working on improving the template > emission strategy during the last couple of releases, i.e. > whether a template instance is emitted to a given object file or > not. Nevertheless, I've been continually hearing complaints from > various people with large D code bases (our commercial users and > some of the more complex open source projects) that they have > problems compiling their code doing anything else than an > all-at-once build. > > This of course detracts from what we like to cite as one of D's > key advantages, compilation speed, because you cannot exploit the > many cores of your build machine anymore, and the > edit-compile-debug cycle is slowed down because you have to build > the full application every time. But this turns into a severe > problem as soon as your compilation does not fit into RAM > anymore, which happens quite quickly when using D's advanced > features – see for example Liran Zvibel's DConf talk, where he > describes that they needed machines with more than 100 GB of RAM > in order to build the Weka code base. > > In any case, I hope you agree that fixing these kinds of issues > that prevent D code from being compiled all is strategically > important for us, since they are a deciding factor in driving > widespread adoption. Sadly, the template problems didn't seem to > receive a lot of attention beyond quick fixes recently, possibly > because they don't occur as readily for smaller projects and if > so, are easier to work around. > > With all that out of my system, I'd like to point your attention > to a particular template instantiation issue I managed to reduce > recently when working with the folks at Weka. It seems like there > is a fundamental oversight in the way the code tries to elide > repeat code generation of instances – or, of course, I'm just > missing something: > > https://issues.dlang.org/show_bug.cgi?id=15318 > > This is one particular issue that makes writing "idiomatic D" > (which is rather template-heavy) in large code bases hard, but > likely not the only one. In fact, I already know about another > issue where function-local imports cause semantic analysis not to > be properly run on template instances, but I'm still struggling > to find a minimal example for the problem. My hope would be that > we can clean up this mess soon and replace the current ad-hoc > patchwork with a more principled approach. In the process, we > should also make sure that all of our assumptions [1] about the > compilation process are clearly stated in the documentation, as > that frequently leads to confusion among newcomers. > > Best, > David > > > > [1] That is: All imported modules must also be compiled into the > executable; incremental compilation is only guaranteed to work if > precisely the same subsets of modules are compiled every time. http://forum.dlang.org/thread/[email protected]
