Re: [boost] [xpressive] Problem accessing repeating embedded pattern.

From: Bjørn Roald (bjorn_at_[hidden])
Date: 2006-01-03 17:05:21

On Tuesday 03 January 2006 22:00, Eric Niebler wrote:
> Bjørn Roald wrote:
> > On Tuesday 03 January 2006 10:43, Eric Niebler wrote:
> >>>You'll notice that I eliminated your name_value_pair_ regex. That's
> >>>because it exposed a bug in xpressive. :-P
> >>
> >>Fixed. Please get the latest version of xpressive from the Vault.
> >
> > I tried to use the xpressive library from the Boost CVS and I ran into
> > some problems.  Do I understand the above to mean that the Vault version
> > is a better choice?
>
> No, the Vault is pretty much the same as what is in CVS at the moment.
> What is the problem you're seeing?

Using static regexp to create simple grammars I encountered two problems.

1. 
The example code for nested grammar in the documentation produced only 
printout of part of the results compared to the documentation.  

2.
Creating a more complex grammar with static regexp I encountered core dumps 
attempting to print nested matches.  Call stack is listed below.  I suspect it 
is related to my lack of understanding the static regexp 
features/rules/limitations.  I am atempting to use nested regexp in the 
grammar that match stuff like C++ comments and literal strings, when I remove 
them it all works better.  I have read that regexp in general break if you 
nest unlimited lenght specifiers like + or *.  Can that be what causes the 
core dump?  If this is the case, is this a limitation we have to live with?  
Any workaround?

If you like me to post the code I can reduce it as much as I can first.

---
Bjørn
Call Stack:
 (gdb) bt
#0  0x0805648b in std::ostream_iterator<char, char, 
std::char_traits<char>>::operator= (this=0xbfe80af0, __value=@0x0) at 
stream_iterator.h:196
#1  0x0805be0d in std::__copy<char const*, std::ostream_iterator<char, char, 
std::char_traits<char> > > (__first=0x0, __last=0x8c3bd13 "}..\" .. {dfgdg()
{aa} fddd \"dffdfd\\\"dfdfgg\"}{bb}ddd // ", 'g' <repeats 12 times>, 
"\nddd // ostekake\nddd // pannekake\n/*\n", 'd' <repeats 12 times>, 
"\n*/\n/*", 'e' <repeats 15 times>, "*/\n}\n\n", 
__result={<std::iterator<std::output_iterator_tag,void,void,void,void>> = 
{<No data fields>}, _M_stream = 0x1c7280, _M_string = 0x0}) at 
stl_algobase.h:247
#2  0x08059bf3 in std::__copy_aux2<char const*, std::ostream_iterator<char, 
char, std::char_traits<char> > > (__first=0x0, __last=0x8c3bd13 "}..\" .. 
{dfgdg(){aa} fddd \"dffdfd\\\"dfdfgg\"}{bb}ddd // ", 'g' <repeats 12 times>, 
"\nddd // ostekake\nddd // pannekake\n/*\n", 'd' <repeats 12 times>, 
"\n*/\n/*", 'e' <repeats 15 times>, "*/\n}\n\n", 
__result={<std::iterator<std::output_iterator_tag,void,void,void,void>> = 
{<No data fields>}, _M_stream = 0x1c7280, _M_string = 0x0}) at 
stl_algobase.h:273
#3  0x08056453 in std::__copy_ni2<char const*, std::ostream_iterator<char, 
char, std::char_traits<char> > > (__first=0x0, __last=0x8c3bd13 "}..\" .. 
{dfgdg(){aa} fddd \"dffdfd\\\"dfdfgg\"}{bb}ddd // ", 'g' <repeats 12 times>, 
"\nddd // ostekake\nddd // pannekake\n/*\n", 'd' <repeats 12 times>, 
"\n*/\n/*", 'e' <repeats 15 times>, "*/\n}\n\n", __result=Cannot access 
memory at address 0x0
) at stl_algobase.h:308
#4  0x08054719 in std::__copy_ni1<__gnu_cxx::__normal_iterator<char const*, 
std::string>, std::ostream_iterator<char, char, std::char_traits<char> > > 
(__first={_M_current = 0x0}, __last={_M_current = 0x8c3bd13 "}..\" .. 
{dfgdg(){aa} fddd \"dffdfd\\\"dfdfgg\"}{bb}ddd // ", 'g' <repeats 12 times>, 
"\nddd // ostekake\nddd // pannekake\n/*\n", 'd' <repeats 12 times>, 
"\n*/\n/*", 'e' <repeats 15 times>, "*/\n}\n\n"}, __result=Cannot access 
memory at address 0x0
) at stl_algobase.h:317
#5  0x080523bb in std::copy<__gnu_cxx::__normal_iterator<char const*, 
std::string>, std::ostream_iterator<char, char, std::char_traits<char> > > 
(__first={_M_current = 0x0}, __last={_M_current = 0x8c3bd13 "}..\" .. 
{dfgdg(){aa} fddd \"dffdfd\\\"dfdfgg\"}{bb}ddd // ", 'g' <repeats 12 times>, 
"\nddd // ostekake\nddd // pannekake\n/*\n", 'd' <repeats 12 times>, 
"\n*/\n/*", 'e' <repeats 15 times>, "*/\n}\n\n"}, __result=Cannot access 
memory at address 0x0
) at stl_algobase.h:358
#6  0x08050be8 in boost::xpressive::operator<< 
<__gnu_cxx::__normal_iterator<char const*, std::string>, char, 
std::char_traits<char> > (sout=@0x1c7280, sub=@0x8c3be70) at 
sub_match.hpp:139
#7  0x080524d3 in 
output_nested_results::operator()<__gnu_cxx::__normal_iterator<char const*, 
std::string> > (this=0xbfe80d3c, what=@0x8c3bc20) at test1.cpp:28
#8  0x08050ca6 in 
std::for_each<std::_List_const_iterator<boost::xpressive::match_results<__gnu_cxx::__normal_iterator<char 
const*, std::string> > >, output_nested_results> (__first={_M_node = 
0x8c3bc18}, __last={_M_node = 0xbfe80e38}, __f={tabs_ = 0}) at stl_algo.h:158
#9  0x0804ec89 in main () at test1.cpp:94