There seems to be a bug in the string algorithm library that results in a valid container iterator being compared to a "singular" default constructed iterator: this operation is not supported by the iterator requirements and results in an assertion being thrown when testing with VC7.1+STLPort (or any other compiler with STLPort for that matter). The call stack is: stlport_vc71_stldebug46.dll!_STL::__stl_debug_engine<bool>::_Terminate() Line 324 C++ stlport_vc71_stldebug46.dll!_STL::__stl_debug_engine<bool>::_Assert(const char * __expr=0x0057420c, const char * __f=0x00574180, int __l=0x0000012d) Line 308 C++ regex_test.exe!_STL::operator==<_STL::_Nondebug_string<char,_STL::char_trait s<char>,_STL::allocator<char> > >(const _STL::_DBG_iter_base<_STL::_Nondebug_string<char,_STL::char_traits<char>,_ST L::allocator<char> > > & __x={...}, const _STL::_DBG_iter_base<_STL::_Nondebug_string<char,_STL::char_traits<char>,_ST L::allocator<char> > > & __y={...}) Line 301 + 0x2e C++ regex_test.exe!boost::algorithm::iterator_range<_STL::_DBG_iter<_STL::_Nonde bug_string<char,_STL::char_traits<char>,_STL::allocator<char>
,_STL::_Const_traits<char> > ::operator==<_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits< char>,_STL::allocator<char> >,_STL::_Const_traits<char> > >() Line 119 + 0x47 C++
regex_test.exe!boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondeb ug_string<char,_STL::char_traits<char>,_STL::allocator<char>
,_STL::_Const_traits<char> > >::equal(const boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<char, _STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char> > & Other={...}) Line 147 + 0x12 C++
regex_test.exe!boost::iterator_core_access::equal<boost::algorithm::find_ite rator<_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_S TL::allocator<char> >,_STL::_Const_traits<char> >
,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
() Line 518 C++
regex_test.exe!boost::operator==<boost::algorithm::find_iterator<_STL::_DBG_ iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<cha r> >,_STL::_Const_traits<char> >
,boost::algorithm::iterator_range<_STL::_DBG_iter<_STL::_Nondebug_string<ch ar,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
const ,boost::forward_traversal_tag,boost::algorithm::iterator_range<_STL::_DBG_it er<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > > const &,int,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string <char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > ,boost::algorithm::iterator_range<_STL::_DBG_iter<_STL::_Nondebug_string<ch ar,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char> const ,boost::forward_traversal_tag,boost::algorithm::iterator_range<_STL::_DBG_it er<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > > const &,int>(const boost::iterator_facade<boost::algorithm::find_iterator<_STL::_DBG_iter<_STL: :_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > ,boost::algorithm::iterator_range<_STL::_DBG_iter<_STL::_Nondebug_string<ch ar,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char> const ,boost::forward_traversal_tag,boost::algorithm::iterator_range<_STL::_DBG_it er<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > > const &,int> & lhs={...}, const boost::iterator_facade<boost::algorithm::find_iterator<_STL::_DBG_iter<_STL: :_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > ,boost::algorithm::iterator_range<_STL::_DBG_iter<_STL::_Nondebug_string<ch ar,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char> const ,boost::forward_traversal_tag,boost::algorithm::iterator_range<_STL::_DBG_it er<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_Const_traits<char> > > const &,int> & rhs={...}) Line 819 + 0x32 C++
regex_test.exe!boost::iterator_adaptor<boost::transform_iterator<boost::algo rithm::detail::copy_iterator_rangeF<_STL::basic_string<char,_STL::char_trait s<char>,_STL::allocator<char>
,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,boost::algorithm::find_iterator<_ST L::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::alloc ator<char> >,_STL::_Const_traits<char> > ,_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,boost::use_default,_STL::basic_string<char,_STL::char_traits<char>,_STL::a llocator<char> ,boost::use_default>::equal<boost::transform_iterator<boost::algorithm::det ail::copy_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char>,_S TL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,boost::algorithm::find_iterator<_ST L::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL::alloc ator<char> >,_STL::_Const_traits<char> > ,_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,boost::use_default,_STL::basic_string<char,_STL::char_traits<char>,_STL::a llocator<char> >,boost::use_default>() Line 297 + 0x12 C++
regex_test.exe!boost::iterator_core_access::equal<boost::transform_iterator< boost::algorithm::detail::copy_iterator_rangeF<_STL::basic_string<char,_STL: :char_traits<char>,_STL::allocator<char>
,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,boost::transform_iterator<boost::al gorithm::detail::copy_iterator_rangeF<_STL::basic_string<char,_STL::char_tra its<char>,_STL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default> >() Line 518 C++
,_STL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,_STL::basic_string<char,_STL::char_
,boost::forward_traversal_tag,_STL::basic_string<char,_STL::char_traits<cha r>,_STL::allocator<char> ,int,boost::transform_iterator<boost::algorithm::detail::copy_iterator_rang eF<_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,_STL::basic_string<char,_STL::char_
,boost::forward_traversal_tag,_STL::basic_string<char,_STL::char_traits<cha r>,_STL::allocator<char> >,int>(const boost::iterator_facade<boost::transform_iterator<boost::algorithm::detail::c opy_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char>,_STL::al locator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,_STL::basic_string<char,_STL::char_
,boost::forward_traversal_tag,_STL::basic_string<char,_STL::char_traits<cha r>,_STL::allocator<char> >,int> & lhs={...}, const boost::iterator_facade<boost::transform_iterator<boost::algorithm::detail::c opy_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char>,_STL::al locator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default>,_STL::basic_string<char,_STL::char_
regex_test.exe!boost::operator!=<boost::transform_iterator<boost::algorithm: :detail::copy_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char traits<char>,_STL::allocator<char> traits<char>,_STL::allocator<char> traits<char>,_STL::allocator<char> traits<char>,_STL::allocator<char>
,boost::forward_traversal_tag,_STL::basic_string<char,_STL::char_traits<cha r>,_STL::allocator<char> >,int> & rhs={...}) Line 820 + 0x32 C++
regex_test.exe!_STL::__vector<_STL::basic_string<char,_STL::char_traits<char
,_STL::allocator<char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ::_M_range_initialize<boost::transform_iterator<boost::algorithm::detail::c opy_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char>,_STL::al locator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default> >() Line 535 + 0x17 C++
regex_test.exe!_STL::__vector<_STL::basic_string<char,_STL::char_traits<char
,_STL::allocator<char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ::_M_initialize_aux<boost::transform_iterator<boost::algorithm::detail::cop y_iterator_rangeF<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default> >() Line 231 C++
regex_test.exe!_STL::__vector<_STL::basic_string<char,_STL::char_traits<char
,_STL::allocator<char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ::__vector<_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator< char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > <boost::transform_iterator<boost::algorithm::detail::copy_iterator_rangeF<_ STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default> >() Line 248 C++
regex_test.exe!_STL::vector<_STL::basic_string<char,_STL::char_traits<char>, _STL::allocator<char>
,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ::vector<_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<ch ar> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > <boost::transform_iterator<boost::algorithm::detail::copy_iterator_rangeF<_ STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,_STL::_DBG_iter<_STL::_Nondebug_string<char,_STL::char_traits<char>,_STL:: allocator<char> >,_STL::_Const_traits<char> > ,boost::algorithm::find_iterator<_STL::_DBG_iter<_STL::_Nondebug_string<cha r,_STL::char_traits<char>,_STL::allocator<char> >,_STL::_Const_traits<char>
,boost::use_default,boost::use_default> >() Line 164 + 0x93 C++
regex_test.exe!boost::algorithm::iter_find<_STL::vector<_STL::basic_string<c har,_STL::char_traits<char>,_STL::allocator<char>
,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ,_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> > const ,boost::algorithm::detail::find_regexF<boost::reg_expression<char,boost::reg ex_traits<char>,_STL::allocator<char> > > (_STL::vector<_STL::basic_string<char,_STL::char_traits<char>,_STL::allocat or<char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > > & Result={...}, const _STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> > & Input={...}, boost::algorithm::detail::find_regexF<boost::reg_expression<char,boost::rege x_traits<char>,_STL::allocator<char> > > Finder={...}) Line 97 + 0x7e C++
regex_test.exe!boost::algorithm::find_all_regex<_STL::vector<_STL::basic_str ing<char,_STL::char_traits<char>,_STL::allocator<char>
,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > ,_STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> ,char,boost::regex_traits<char>,_STL::allocator<char> (_STL::vector<_STL::basic_string<char,_STL::char_traits<char>,_STL::allocat or<char> ,_STL::allocator<_STL::basic_string<char,_STL::char_traits<char>,_STL::allo cator<char> > > > & Result={...}, const _STL::basic_string<char,_STL::char_traits<char>,_STL::allocator<char> > & Input={...}, const boost::reg_expression<char,boost::regex_traits<char>,_STL::allocator<char> > & Rx={...}, boost::regex_constants::_match_flags Flags=match_default) Line 429 + 0x2b C++ regex_test.exe!find_test() Line 68 + 0x16 C++ regex_test.exe!test_main(int __formal=0x00000001, int __formal=0x00000001) Line 134 C++ regex_test.exe!`anonymous namespace'::call_test_main() Line 37 + 0x12 C++ regex_test.exe!boost::unit_test::function_test_case::do_run() Line 138 + 0x2b C++ regex_test.exe!boost::unit_test::ut_detail::unit_test_monitor::function() Line 77 + 0x14 C++ regex_test.exe!boost::execution_monitor::run_function() Line 188 + 0x54 C++ regex_test.exe!boost::detail::catch_signals(boost::execution_monitor & exmon={...}, bool __formal=true, bool __formal=true) Line 472 C++ regex_test.exe!boost::execution_monitor::execute(bool catch_system_errors=true, int timeout=0x00000000) Line 211 + 0x11 C++
regex_test.exe!boost::unit_test::ut_detail::unit_test_monitor::execute_and_t ranslate(boost::unit_test::test_case * target_test_case=0x009c9990, void (void)* f=0x0047d339, int timeout=0x00000000) Line 43 + 0x13 C++ regex_test.exe!boost::unit_test::test_case::run() Line 145 + 0x6c C++ regex_test.exe!main(int argc=0x00000001, char * * argv=0x009c6bb8) Line 83 C++ And the actual problem I think is caused by (iter_find.hpp#98): transform_iter_type itBegin= make_transform_iterator( find_iterator_type( begin(Input), InputEnd, Finder ), copy_range_type()); transform_iter_type itEnd= make_transform_iterator( find_iterator_type(), // end iterator is default constructed here!! copy_range_type()); SequenceSequenceT Tmp(itBegin, itEnd); // assertion here There may be other occurances of course, this is just the first assertion to be triggered... John.