On Feb 14, 2014, at 4:31 PM, David Blaikie <[email protected]> wrote:
> On Fri, Feb 14, 2014 at 4:21 PM, Marshall Clow <[email protected]> wrote:
> Users can write
> for(sregex_iterator i(s.begin(), s.end(), regex("meow")), end; i !=
> end; ++i)
>
> binding a temporary regex to const regex& and storing a pointer to it.
> This will compile silently, triggering undefined behavior at runtime.
>
> Fixing this involves defining constructors for the various regex iterator
> types from rvalue regexes, and then marking them as “deleted”.
> And tests.
>
> Would this break (what I assume is) correct code doing things like:
>
> std::find(sregex_iterator(s.begin(), s.end(), regex("meow")), end, "foo”); ?
(Recapping a discussion on IRC)
Yes, it would.
And though that code is "technically correct” it (a) is dangerous, and (b)
doesn’t do anything useful.
The return result from std::find is an interator into a destroyed object, so
you can’t really do anything with that.
The “fix” for this code is simple:
regex re{“meow”}
std::find(sregex_iterator(s.begin(), s.end(), re), end, "foo”);
and now the return value of std::find is valid (until the end of the lifetime
of “re”).
See
http://cplusplus.github.io/LWG/lwg-active.html#2329
and http://cplusplus.github.io/LWG/lwg-active.html#2332
for the changes to the (C++14) standard.
— Marshall
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