- Boost-users - lists.preview.boost.org

Iterators
by Colin Fox 21 Feb '02

21 Feb '02

This isn't a boost specific message per se, I guess, but I thought someone here may know the answer. I have a list<> of smart_ptrs. Some of the elements in the list are ready for processing under various circumstances. What I'd like would be a custom iterator that when I say "++i" it checks the element to see if it's ready, and if not, advance to the next, and so on until it finds a ready element. If it doesn't find one, then i == list.end(). This would simulate having a list that contained only ready elements, without having to have multiple lists. I have a number of books on C++, but I can't figure out from them how to create a custom iterator. Can anyone help? -- Colin Fox CF Consulting Inc. cfox(a)crystalcherry.com

2 1

[BGL] BGL Book Erratum
by Eric Eide 21 Feb '02

21 Feb '02

Page 12, Figure 1.2: the edge (a,d) should be black, and (b,d) should be gray. ...unless `breadth_first_search' is using the `delay_map' in some way that is not obvious to me. Eric. -- ------------------------------------------------------------------------------- Eric Eide <eeide(a)cs.utah.edu> . University of Utah School of Computing http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

2 1

const smart pointers
by nckgl 21 Feb '02

21 Feb '02

how do I define const smart pointer? for example for "int" type 1. scoped_ptr<const int> 2. const scoped_ptr<int> If the latter then it may be better to re-define get() as follows T* get(){ return px; } // never throws const T* get()const { return px; } // never throws Now scoped_ptr::get() is defined as follows T* get() const { return px; } // never throws The same apply to other accessors (operator-> and so on)

2 1

Problem linking with regex on Win32
by Dale Peakall 21 Feb '02

21 Feb '02

I'll try and add some content before sending a message this time ;) Platform: 2K Compiler: VC6 SP5 Library: stlport-4.0 Boost: 1.27.0 Build Tool for Boost: Jam Run-time Library: Multithreaded DLL/Debug Multithreaded DLL I've got a couple of problems trying to get my app to link against regex. I've tried linking to the debug and release versions of both the DLL and non-DLL versions of the regex library and in each case I get errors about unresolved external symbols for w32_regex_traits. w32_regex_traits.obj has been produced by Jam. In addition the static version winges about lots of locally defined symbols. I've specified BOOST_REGEX_NO_LIB as the generated filenames are not what Jam produces. Here's the full details: --------------------Configuration: request_line_test - Win32 Debug-------------------- Linking... http_request_line.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: static void __cdecl boost::w32_regex_traits<char>::transform_primary(class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<c har> > &,class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<char> > const &)" (__imp_?transform_primary@?$w32_regex_traits@D@boost@@SAXAAV?$basic_string@D U?$char_traits@D@std@@V?$allocator@D@_STL@@@_STL@@ABV34@@Z) http_request_line.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: static bool __cdecl boost::w32_regex_traits<char>::lookup_collatename(class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator< char> > &,char const *,char const *)" (__imp_?lookup_collatename@?$w32_regex_traits@D@boost@@SA_NAAV?$basic_string @DU?$char_traits@D@std@@V?$allocator@D@_STL@@@_STL@@PBD1@Z) http_request_line.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: __thiscall boost::bad_expression::bad_expression(class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<char> > const &)" (__ imp_??0bad_expression@boost@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V? $allocator@D@_STL@@@_STL@@@Z) http_request_line.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: static class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<char> > __cdecl boost::re_detail::w32_traits_base::error_strin g(unsigned int)" (__imp_?error_string@w32_traits_base@re_detail@boost@@SA?AV?$basic_string@DU ?$char_traits@D@std@@V?$allocator@D@_STL@@@_STL@@I@Z) http_request_line.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: static void __cdecl boost::w32_regex_traits<char>::transform(class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<char> > & ,class _STL::basic_string<char,struct std::char_traits<char>,class _STL::allocator<char> > const &)" (__imp_?transform@?$w32_regex_traits@D@boost@@SAXAAV?$basic_string@DU?$char_ traits@D@std@@V?$allocator@D@_STL@@@_STL@@ABV34@@Z) Debug/request_line_test.exe : fatal error LNK1120: 5 unresolved externals Error executing link.exe. request_line_test.exe - 6 error(s), 0 warning(s) Thanks, - Dale.

1 0

scoped_try_lock
by schalk_cronje＠nai.com 20 Feb '02

20 Feb '02

I was wondering about this line in boost::detail::thread::scoped_try_lock: if(m_locked) throw lock_error(); Since it is known that the lock attempt might fail and we do not want to block until the lock becomes available, is it not better to simply return false in the above case instead of throwing lock_error? ----------------------------------[ .signature ]--- Schalk W. Cronjé, Codernaut, Webshield Engineering, Network Associates. ++C or C++ ?

2 1

Permutation Iterator Adaptor Problem
by Jeff Flinn - wwnet 20 Feb '02

20 Feb '02

I'm trying to use the Permutation Iterator adaptor on MSV++ w/SP5 with boost_1_27_0. Below is a simplification of the example on the web site, which results in the compiler error found below function main: Any ideas? #include <list> #include <vector> #include <boost/permutation_iterator.hpp> int main(int argc, char* argv[]) { typedef std::vector < int > tElements; typedef tElements::iterator tEItr; typedef std::list < int > tIdxs; typedef tIdxs::iterator tIItr; typedef std::ostream_iterator< int > tOItr; tElements elements( 1, 1 ); tIdxs indices ( 1, 1 ); typedef boost::permutation_iterator_generator< tEItr, tIItr >::type tPItr; tPItr begin = boost::make_permutation_iterator( elements.begin(), indices.begin() ); int val = *begin; return 0; } error C2440: 'initializing' : cannot convert from 'struct boost::detail::iterator_traits_::undefined<void>' to 'int' Source or target has incomplete type

5 8

boost::regex compilation errors on RedHat 7.1/gcc 2.96
by John Maddock 19 Feb '02

19 Feb '02

>I'm new to boost and I'm primarily interested in the regex library but I get >some scary looking errors when trying to compile on RedHat. I imagine that >someone must have tried this already. >Thanks for any help you can offer. Unfortunately it's a known problem with gcc 2.96 (which was never officially released remember), gcc 2.95.x or gcc 3.x are both fine however. If anyone has a fix for redhat 2.96 gcc then I'd be happy to apply any patches - but it's not a gcc version I have access to. - John Maddock http://ourworld.compuserve.com/homepages/john_maddock/

1 0

boost.function as parameter of class template
by richielee616 19 Feb '02

19 Feb '02

I want to use boost.function object as a parameter of class template: template< function1<void,int> F > class foo { // ... }; but VC6 tells me "F : template parameter can never be initialized" why?

3 2

boost::regex compilation errors on RedHat 7.1/gcc 2.96
by Gerry Woods 18 Feb '02

18 Feb '02

Hi, I'm new to boost and I'm primarily interested in the regex library but I get some scary looking errors when trying to compile on RedHat. I imagine that someone must have tried this already. Thanks for any help you can offer. Gerry >uname -a Linux gloria.we.mediaone.net 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2001 i686 unknown >gcc -v Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs gcc version 2.96 20000731 (Red Hat Linux 7.1 2.96-81) >make -f gcc.mak g++ -o gcc/boost_regex/cregex.o -c -O2 -I../../../ ../src/cregex.cpp ../../../boost/regex.hpp: In function `iterator boost::re_detail::re_is_set_member (iterator, iterator, const boost::re_detail::re_set_long *, const boost::reg_expression<charT, traits_type, Allocator> &) [with iterator = boost::re_detail::mapfile_iterator, charT = char, traits_type = boost::regex_traits<char>, Allocator = allocator<char>]': ../../../boost/regex/detail/regex_match.hpp:600: instantiated from `boost::re_detail::query_match_aux (iterator, iterator, boost::match_results<iterator, Allocator> &, const boost::reg_expression<charT, traits, Allocator2> &, unsigned int, boost::re_detail::_priv_match_data<iterator, Allocator> &, iterator *) [with iterator = boost::re_detail::mapfile_iterator, Allocator = allocator<char>, charT = char, traits = boost::regex_traits<char>, Allocator2 = allocator<char>]' ../../../boost/regex/detail/regex_match.hpp:1177: instantiated from `boost::re_detail::reg_grep2 (Predicate, I, I, const boost::reg_expression<charT, traits, Allocator2> &, unsigned int, A2) [with Predicate = boost::re_detail::pred4, I = boost::re_detail::mapfile_iterator, charT = char, traits = boost::regex_traits<char>, A = allocator<char>, A2 = allocator<char>]' ../../../boost/regex/detail/regex_match.hpp:1836: instantiated from `boost::regex_grep (Predicate, iterator, iterator, const boost::reg_expression<charT, traits, Allocator2> &, unsigned int) [with Predicate = boost::re_detail::pred4, iterator = boost::re_detail::mapfile_iterator, charT = char, traits = boost::regex_traits<char>, Allocator = allocator<char>]' ../src/cregex.cpp:387: instantiated from here ../../../boost/regex.hpp:244: Internal compiler error in scan_region, at except.c:2809 Please submit a full bug report. See <URL:http://bugzilla.redhat.com/bugzilla/> for instructions. make: *** [gcc/boost_regex/cregex.o] Error 1

1 0

Threads and Smart Ptrs
by Colin Fox 16 Feb '02

16 Feb '02

Greetings, everyone. I'm currently having some trouble with a heavily multithreaded app which uses objects shared between threads via smart pointers. It's a multi-user application, where each user has a thread, and when one user sends a message to another (or broadcasts to all), a message object is created, and a smart pointer to that message is put into a queue for each thread. I'm using pthread_mutex for locking the queues for each thread. This program will sometimes work flawlessly for hours, and other times it will die within moments of starting. Pretty much every time it dies, it's because the message object has been freed while there are still smart pointers pointing to it. I know that the recent version of the smart pointer library was supposed to have added thread-safety to it, but I'm wondering if anyone else is having similar troubles. I'm using gcc 3.0.3 on Linux, and boost 1.27. I also discovered some things in the gcc documentation having to do with threads, (eg: when you compile the compiler, you have to tell it to build multi-threaded programs). And there are various threading flags that can be used during a compile, and I'm not sure which to use (or all of them?): -D_PTHREADS -D_REENTRANT -pthread : I'm using all those right now. Is that wrong? Any help would be greatly appreciated. It's driving me mad! :) Regards, Colin -- Colin Fox CF Consulting Inc. cfox(a)telus.net

3 8