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

[Clemens Hintze]

Nathaniel Smith wrote:
> On Sat, Jan 21, 2006 at 03:11:51AM -0600, Timothy Brownawell wrote:

(...)

> > Aren't strings copy-on-write anyway, so this shouldn't be a problem?
>
>
> Oh, hrm.  That's a clever point.

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.


Best regards,
Clemens.