id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
1990	xpressive: passing temporary regex to sregex_token_iterator causes runtime assertion	jesse@…	Eric Niebler	"This program suprises me by causing a runtime assertion:

{{{
#include <string>
#include <boost/xpressive/xpressive.hpp>

using namespace boost::xpressive;

int main()
{
 std::string x(""a\tb\tc"");

 sregex_token_iterator   cur(x.begin(), x.end(), as_xpr(""\t""), -1),
                         end;
 for(; cur != end; ++cur)
  ;
}
}}}

...the assertion:

{{{
suprise: /usr/local/include/boost-1_35/boost/xpressive/detail/utility/tracking_ptr.hpp:196: void
boost::xpressive::detail::enable_reference_tracking<Derived>::release() [with Derived = boost::xpressive::detail::regex_impl<__gnu_cxx::__normal_iterator<const char*,
std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]: Assertion `0 < this->cnt_' failed.
Aborted
}}}

Changing the declarations like this causes it to work as I expect:

{{{
 sregex tab_delim(as_xpr(""\t""));
 sregex_token_iterator   cur(x.begin(), x.end(), tab_delim, -1),
                         end;
}}}

...maybe there's some ""temporary"" magic happening, or that I was just plain doing something I shouldn't have been doing (silly me!), or both? 

[Note: Boost 1.35, OpenSuSE 10.3, g++ 4.1.2]

Eric Niebler's reply of 4/6/2008:
{{{
Interesting. Currently the regex iterators hold a (bare) pointer to the
regex to be used. If you pass in a temporary regex, it'll obviously not
live long enough. It wouldn't be hard to make the regex iterators hold a
reference count to the regex impl, which would make your code work. The
down-side would be that copying regex iterators (a common operation?)
would be more expensive.
}}}

"	Bugs	closed	Boost 1.36.0	xpressive	Boost 1.35.0	Problem	fixed