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From: Gregory Dai (gregory.dai_at_[hidden])
Date: 2006-09-01 18:26:11

On 9/1/06, John Maddock <john_at_[hidden]> wrote:
> Gregory Dai wrote:
> >> Have I got that right?
> >
> >
> > Well, not completely perhaps. E.g., at least if the target is a
> > std::string of size=0, the resultant std::string may well be
> > reference-counted and shared by multiple threads.
> Can you explain some more? Are you saying that if two unrelated threads
> each default construct a string (or maybe construct a zero length string?)
> then they will be entangled by reference counting?

Well, I don't have definitive proof, but that's possible from my experience.

E.g., we have many classes with ctors like this: ctor(..., std::string
const& s = std::string());
More than a few developers had such experience that a crash could well be
made disappear by changing the type of "s" to char const* (and, of course,
passing whatever the string as string.c_str() to the ctor).

We just had too many of it (and for a few other reasons) our solution was
eventually replacing std::string with one that does not use the
copy-on-write technique.

Thanks, John.
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