Re: [Monotone-devel] Copy-on-write not mandated! (Was: Typesafe VA_ARGS replacement for database::execute/fetch)

[Nathaniel Smith]

On Sun, Jan 22, 2006 at 08:53:45AM +0100, Clemens Hintze wrote:
> Sorry for bothering, but - while it is true, that the C++ standard was 
> written in a manner that allow copy-on-write technics for implementation 
> of basic_string, it does not mandate to do so!
> 
> Further it seems, that there are situations, where copy-on-write will 
> behave worser than a simple plain implementation - thread safety comes 
> to mind. See for example
> 
>    http://www.gotw.ca/publications/optimizations.htm
> 
> In this light it could not being impossible, that STL vendors could 
> leave the copy-on-write path.

Yes.  But it happens that
  1) monotone currently only builds on g++ (or if not, then certainly
     by far the vast majority of its use is with g++, on all major
     platforms)
  2) we know that in fact g++'s std::string is CoW, so can optimize
     with that in mind

-- Nathaniel

-- 
Details are all that matters; God dwells there, and you never get to
see Him if you don't struggle to get them right. -- Stephen Jay Gould