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strange linker error with boost::function
by Noah Roberts 28 Jul '09

28 Jul '09

Can anyone think why I would get an unresolved symbol on this monstrosity from the liker: public: __thiscall boost::function< class std::auto_ptr<struct esi::command::command> __cdecl(class std::vector< struct esi::draw::primitives::point_impl<double> ,class std::allocator<struct esi::draw::primitives::point_impl<double> > > const & ) > ::function < class std::auto_ptr<struct esi::command::command> __cdecl(class std::vector< struct esi::draw::primitives::point_impl<double> ,class std::allocator<struct esi::draw::primitives::point_impl<double> > > const & ) > < class std::auto_ptr<struct esi::command::command> (__cdecl*)(class std::vector< struct esi::draw::primitives::point_impl<double> ,class std::allocator<struct esi::draw::primitives::point_impl<double> > > const & ) > (class std::auto_ptr<struct esi::command::command> (__cdecl*)(class std::vector< struct esi::draw::primitives::point_impl<double> ,class std::allocator<struct esi::draw::primitives::point_impl<double> > > const & ) ,int ) I tried to clean it up a bit. Looks to me like there's no instantiation of the appropriate constructor to the function template. I tried to recreate the problem in a simple sample but can't seem to do it. Hoping that I'm falling foul of a common issue that someone might be able to just give me pointers toward fixing.

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null instruction ptr bugcheck in regexp
by Heidi Zhou 28 Jul '09

28 Jul '09

Hello! I am using boost regexp to do string/expression match. I got several dump files that have the same call stack when the crash happends. What my code does is copying user buffer (containing string to be mached) to an internal allocated buffer and then call boost regexp functions. From the following result of windbg's "analyze", can you tell what cause the null intrstrucation ptr? I check the memory that contains the string to macht and didn't find any wrong. Also, btw, where can I find boost pdb? Thank you. ==================================================== FAULTING_IP: +0 00000000 ?? ??? EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 00000000 ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 00000000 Attempt to read from address 00000000 PROCESS_NAME: nlca_service.exe ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at "0x%08lx" referenced memory at "0x%08lx". The memory could not be "%s". EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at "0x%08lx" referenced memory at "0x%08lx". The memory could not be "%s". EXCEPTION_PARAMETER1: 00000000 EXCEPTION_PARAMETER2: 00000000 READ_ADDRESS: 00000000 FOLLOWUP_IP: nlca_framework+4578a 1004578a 84c0 test al,al FAILED_INSTRUCTION_ADDRESS: +0 00000000 ?? ??? NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 00000574 BUGCHECK_STR: APPLICATION_FAULT_NULL_INSTRUCTION_PTR_INJECTED_CRASH PRIMARY_PROBLEM_CLASS: NULL_INSTRUCTION_PTR DEFAULT_BUCKET_ID: NULL_INSTRUCTION_PTR LAST_CONTROL_TRANSFER: from 1004578a to 00000000 STACK_TEXT: WARNING: Frame IP not in any known module. Following frames may be wrong. 0134fd08 1004578a 0134fde8 00000001 10036e74 0x0 0134fd14 10036e74 00000008 0134fde8 00000002 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>> ,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_all_states+0x9a 0134fd4c 1004578a 0134fde8 0114229c 10046239 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_startmark+0x194 0134fd58 10046239 0134fde8 10046370 0112fea4 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_all_states+0x9a 0134fd60 10046370 0112fea4 006ba6e0 0134fda8 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_prefix+0x39 0134fd78 10049e71 eaa88d5d 0112fea4 006ba6e0 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::find_restart_any+0xe0 0134fda8 10036cc8 eaa88d41 100606e8 0134fde8 nlca_framework!boost::re_detail::abstract_protected_call::execute+0x41 0134fdc8 10046f4a 10046b40 10010cbc eaa88d29 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::protected_call+0x48 0134fdd0 10010cbc eaa88d29 0112fea4 006ba6e0 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::find+0xa 0134fe78 100112bb 0112fea4 0114e3c8 0112fea4 nlca_framework!boost::regex_search<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>> ,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,wchar_t,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >+0xac 0134ff24 1001166d 0112fea4 006ba6e0 00000000 nlca_framework!NLCA::ContentAnalysisRPCTask::`scalar deleting destructor'+0x12b 0134ff48 72881657 00000007 0112fea4 0113ff00 nlca_framework!NLCA::ContentAnalysisRPCTask::CloneTask+0x1cd 0134ff98 7288880f 0016b8f0 00000001 00000000 vcomp!_vcomp::ParallelRegion::HandlerThreadFunc+0xd7 0134ffb4 7c80b729 0016b880 00000000 00000000 vcomp!_vcomp::NullAPCFunc+0x7f 0134ffec 00000000 728887d0 0016b880 00000000 kernel32!BaseThreadStart+0x37 SYMBOL_STACK_INDEX: 1 SYMBOL_NAME: nlca_framework+4578a FOLLOWUP_NAME: MachineOwner MODULE_NAME: nlca_framework IMAGE_NAME: nlca_framework.dll DEBUG_FLR_IMAGE_TIMESTAMP: 49950ed6 STACK_COMMAND: ~11s; .ecxr ; kb FAILURE_BUCKET_ID: NULL_INSTRUCTION_PTR_c0000005_nlca_framework.dll!Unknown BUCKET_ID: APPLICATION_FAULT_NULL_INSTRUCTION_PTR_INJECTED_CRASH_NULL_IP_nlca_framework+4578a Followup: MachineOwner --------- Heidi

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Boost::Function - Preferred Form Detection
by ryull＠kaladorstudios.com 28 Jul '09

28 Jul '09

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[function_traits] How to detect function arity for functors with member template?
by jesseperla 28 Jul '09

28 Jul '09

I am interested in tag dispatching in a generic function depending on whether the passed in argument is arity 1 or 2. My problem is that I want to have a generic expectation operator that is passed in a function to take the expectation over, and a distribution for the integration. The expectation needs to support both real and mixed-integer measures and functions. Consider the following functions it should work with: struct my_real_functor { template<std::size_t N> double operator()(ublas::bounded_vector<double,N>& x) {...} }; template<std::size_t N> double my_real_function(ublas::bounded_vector<double,N>& x) {...} struct my_mixed_functor { template<std::size_t RealN, std::size_t IntN> double operator()(ublas::bounded_vector<double,RealN>& real_x, ublas::bounded_vector<int,RealN>& int_x) {...} }; .... naturally, part of the problem is that the functor could have both specializations, so I recognize this might be tricky. If both are on a functor, then I can default to one of the implementations(probably the unary) for the matching. --------------------------------------------------- For the operator itself, the signature would be something like. <class F, class Distribution> double expectation(F f, const Distribution& dist) { .....// tag dispatch depending on F arity, or something similar. } ..... or even better: <class F, class Distribution> double expectation(mpl::enable_if<has_unary,F>::type f, const Distribution& dist) { .....//unary implementation } <class F, class Distribution> double expectation(mpl::enable_if<has_binary,F>::type f, const Distribution& dist) { .....// binary implementation. } .... or even better if I could fully match the signatures of the passed in F for conformance. ------------------------------------------------------ I looked at boost function_traits but it doesn't work with member functors.... http://www.boost.org/doc/libs/1_39_0/libs/type_traits/doc/html/boost_typetr… Any ideas on how best to implement this? Thanks as always, Jesse

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Re: [Boost-users] null instruction ptr bugcheck in regexp
by Heidi Zhou 28 Jul '09

28 Jul '09

I havn't received replies on this, and wonder where is the correct place that I should post this kind question. I got full stack using VS 2005. It tells that register EBP is corrupted in the function boost::re_detail::abstract_protected_call::execute. Before this function, the value of EBP value is correct. Is there any similar problem that has been known already? Thank you. Heidi On Fri, Jul 24, 2009 at 3:52 PM, Heidi Zhou <heidi_zhou(a)yahoo.com> wrote: >Hello! > >I am using boost regexp to do string/expression match. I got several dump files that have the same call stack when the crash happends. What my code does is copying user buffer (containing string to be mached) to an internal allocated buffer and then call boost regexp functions. > >>From the following result of windbg's "analyze", can you tell what cause the null intrstrucation ptr? I check the memory that contains the string to macht and didn't find any wrong. > >Also, btw, where can I find boost pdb? > >Thank you. > >==================================================== >FAULTING_IP: >+0 >00000000 ?? ??? > >EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) >ExceptionAddress: 00000000 > ExceptionCode: c0000005 (Access violation) > ExceptionFlags: 00000000 >NumberParameters: 2 > Parameter[0]: 00000000 > Parameter[1]: 00000000 >Attempt to read from address 00000000 > >PROCESS_NAME: nlca_service.exe > >ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at "0x%08lx" referenced memory at "0x%08lx". The memory could not be "%s". > >EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at "0x%08lx" referenced memory at "0x%08lx". The memory could not be "%s". > >EXCEPTION_PARAMETER1: 00000000 > >EXCEPTION_PARAMETER2: 00000000 > >READ_ADDRESS: 00000000 > >FOLLOWUP_IP: >nlca_framework+4578a >1004578a 84c0 test al,al > >FAILED_INSTRUCTION_ADDRESS: >+0 >00000000 ?? ??? > >NTGLOBALFLAG: 0 > >APPLICATION_VERIFIER_FLAGS: 0 > >FAULTING_THREAD: 00000574 > >BUGCHECK_STR: APPLICATION_FAULT_NULL_INSTRUCTION_PTR_INJECTED_CRASH > >PRIMARY_PROBLEM_CLASS: NULL_INSTRUCTION_PTR > >DEFAULT_BUCKET_ID: NULL_INSTRUCTION_PTR > >LAST_CONTROL_TRANSFER: from 1004578a to 00000000 > >STACK_TEXT: >WARNING: Frame IP not in any known module. Following frames may be wrong. >0134fd08 1004578a 0134fde8 00000001 10036e74 0x0 >0134fd14 10036e74 00000008 0134fde8 00000002 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>> ,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_all_states+0x9a >0134fd4c 1004578a 0134fde8 0114229c 10046239 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_startmark+0x194 >0134fd58 10046239 0134fde8 10046370 0112fea4 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_all_states+0x9a >0134fd60 10046370 0112fea4 006ba6e0 0134fda8 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::match_prefix+0x39 >0134fd78 10049e71 eaa88d5d 0112fea4 006ba6e0 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::find_restart_any+0xe0 >0134fda8 10036cc8 eaa88d41 100606e8 0134fde8 nlca_framework!boost::re_detail::abstract_protected_call::execute+0x41 >0134fdc8 10046f4a 10046b40 10010cbc eaa88d29 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::protected_call+0x48 >0134fdd0 10010cbc eaa88d29 0112fea4 006ba6e0 nlca_framework!boost::re_detail::perl_matcher<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >::find+0xa >0134fe78 100112bb 0112fea4 0114e3c8 0112fea4 nlca_framework!boost::regex_search<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>> ,std::allocator<boost::sub_match<std::_String_const_iterator<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > > >,wchar_t,boost::regex_traits<wchar_t,boost::w32_regex_traits<wchar_t> > >+0xac >0134ff24 1001166d 0112fea4 006ba6e0 00000000 nlca_framework!NLCA::ContentAnalysisRPCTask::`scalar deleting destructor'+0x12b >0134ff48 72881657 00000007 0112fea4 0113ff00 nlca_framework!NLCA::ContentAnalysisRPCTask::CloneTask+0x1cd >0134ff98 7288880f 0016b8f0 00000001 00000000 vcomp!_vcomp::ParallelRegion::HandlerThreadFunc+0xd7 >0134ffb4 7c80b729 0016b880 00000000 00000000 vcomp!_vcomp::NullAPCFunc+0x7f >0134ffec 00000000 728887d0 0016b880 00000000 kernel32!BaseThreadStart+0x37 > > >SYMBOL_STACK_INDEX: 1 > >SYMBOL_NAME: nlca_framework+4578a > >FOLLOWUP_NAME: MachineOwner > >MODULE_NAME: nlca_framework > >IMAGE_NAME: nlca_framework.dll > >DEBUG_FLR_IMAGE_TIMESTAMP: 49950ed6 > >STACK_COMMAND: ~11s; .ecxr ; kb > >FAILURE_BUCKET_ID: NULL_INSTRUCTION_PTR_c0000005_nlca_framework.dll!Unknown > >BUCKET_ID: APPLICATION_FAULT_NULL_INSTRUCTION_PTR_INJECTED_CRASH_NULL_IP_nlca_framework+4578a > >Followup: MachineOwner >--------- > > Heidi > > > > >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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General: <unresolved overloaded function type>
by Etienne Philip Pretorius 28 Jul '09

28 Jul '09

Hello List, Just a general question: I am trying to use boost::asio::async_read_until with a these templated functions: template<typename D> struct entity { template<typename T> std::pair<T,bool> operator()( T begin, T end ) { if(begin == end) { return std::make_pair<end,false>; } return static_cast<D*>(this)->impl(begin,end); }; }; /* http://www.w3.org/TR/REC-xml/#NT-S */ struct white_space : entity<white_space> { template<typename T> std::pair<T,bool> impl( T begin, T end ) { for(; begin != end; begin++) { if(*begin == 0x09u || *begin == 0x0Au || *begin == 0x0Du || *begin == 0x20u) { continue; }else{ return std::make_pair<begin,false>; } } return std::make_pair<end,true>; }; }; I get the following error: xml.hpp:146: error: conversion from ‘<unresolved overloaded function type>’ to non-scalar type ‘std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, bool>’ requested At every line that I have a return defined... Could someone please explain to me what I have done wrong here.... Thank you, Etienne

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[program_options] detecting if "arguments" are passed
by Christoph Duelli 28 Jul '09

28 Jul '09

I am using Boost.ProgramOptions to parse my command line options. By default, I an exception is thrown when an unknown option is passed. So far, so good. Suppose I have a program p that takes only the option --help - and nothing else, esp. not a "positional option" or "arguments". I.e. I would like to croak a message to the user if she call something like p /tmp/x ProgramOptions does croak when I call "p -v", but not when I call "p /tmp/x". Question: What is the recommended way to catch unwanted (or forbidden) arguments (not options!)? (I know I can define a positional like --input-file and then check if any of those are present. But that seems quite awkward for such a "simple" thing.) Best regards Christoph

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[newbie] Boost 1.39 in Mac XCode get "error: attempt to copy-construct an iterator from a singular iterator."
by Victor Tsang 28 Jul '09

28 Jul '09

Hi, I'm new to boost. It seems that the coding of boost library is not very clean as it makes the debug code aborted by generating a runtime error like this: "error: attempt to copy-construct an iterator from a singular iterator.". Here are the steps to reproduce the fault: I downloaded the source and install the things to /usr/local/include as well as /usr/local/lib. I test the code by creating a "C++ Tool" project in XCode. 1. Create a new C++ Tool project. 2. Add the header search path /usr/local/include/boost-1_39 and library search path /usr/local/lib into the project. 3. Add "Other Linker Flags" "-lboost_system-xgcc40-mt" in the project setting. 4. Edit the main.cpp as below: #include <iostream> #include<boost/asio.hpp> int main (int argc, char * const argv[]) { boost::asio::io_service io_service; boost::asio::ip::tcp::acceptor acceptor(io_service); std::cout<<"acceptor instantiated."<<std::endl; return 0; } 5. Build and run. Check out the result from the Console window as captured below: [Session started at 2009-07-28 16:00:10 +0800.] * /Developer/SDKs/MacOSX10.5.sdk/usr/include/c++/4.0.0/debug/safe_iterator.h:127: * * error: attempt to copy-construct an iterator from a singular iterator.* ** *Objects involved in the operation:* *iterator "this" @ 0x0x100480 {* *type = N11__gnu_debug14_Safe_iteratorIN10__gnu_norm14_List_iteratorISt4pairIiPN5boost4asio6detail16reactor_op_queueIiE7op_baseEEEEN15__gnu_debug_def4listISB_SaISB_EEEEE (mutable iterator);* * state = singular;* *}* *iterator "other" @ 0x0xbffff364 {* *type = N11__gnu_debug14_Safe_iteratorIN10__gnu_norm14_List_iteratorISt4pairIiPN5boost4asio6detail16reactor_op_queueIiE7op_baseEEEEN15__gnu_debug_def4listISB_SaISB_EEEEE (mutable iterator);* * state = singular;* *}* [Session started at 2009-07-28 16:00:10 +0800.] GNU gdb 6.3.50-20050815 (Apple version gdb-966) (Tue Mar 10 02:43:13 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 3497. The Debugger Debugger is attaching to process It generates a runtime error "error: attempt to copy-construct an iterator from a singular iterator.". However, if I compile the code in terminal: g++ -o test -g -Wall main.cpp -lboost_system-xgcc40-mt It runs okay without any runtime error. Regards, Victor Tsang

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Re: [Boost-users] [Boost.CircularBuffer] begin()/end() arithmetic not working out quite right
by David Baird 27 Jul '09

27 Jul '09

Hi Jan, Thanks for your reply and sorry for taking so long to respond. I am a bit confused by your response. I never did expect begin() to move forward after push_back(). In my original post, what I said is that I expect begin() will remain constant and that **end() will move forward** each time push_back() is called. My main question is this: why does end() remain constant when push_back() is called on a circular_buffer? In other words, why does this assertion fail?: circular_buffer<int> buf(8); circular_buffer<int>::iterator a; circular_buffer<int>::iterator b; a = buf.end(); buf.push_back(1); b = buf.end(); assert(a != b); // fails If I use an STL vector instead of circular_buffer, I get exactly the results I expect (as along as I call .reserve() on it prior, so that iterators are not invalidated by a realloc). -David On Thu, Jun 11, 2009 at 1:58 AM, Jan Gaspar<jano_gaspar(a)yahoo.com> wrote: > > Hi David, > > you just cannot rely on this. I don't think standard says anything about begin() moving forward after push_back(). Correct me if I'm wrong. > > The way how it is implemented is that if the circular_buffer is empty begin() returns the same iterator as end(). > > There is also a note about iterator invalidation for push_back(): > "Does not invalidate any iterators with the exception of iterators pointing to the overwritten element." > > It means iterator 'a' in your first example will point to the same element as it was before calling push_back() - which is end(). This explains the behaviour you are describing. > > Regards, > > Jan > > > > > ----- Original Message ---- > From: David Baird <dhbaird(a)gmail.com> > To: Jan Gaspar <jano_gaspar(a)yahoo.com>; boost-users(a)lists.boost.org > Sent: Thursday, 11 June, 2009 1:01:54 > Subject: [Boost.CircularBuffer] begin()/end() arithmetic not working out quite right > > Hi, > > Firstly, thanks for the work on a circular buffer. This is very > useful since many of my applications require it. I am having a > problem though... > > I am using Boost 1.38.0. When I call push_back(), the iterator math > makes it appear that begin() moves backwards and end() remains > constant. (Based on other STL libraries, I expect that begin() will > remain constant and end() will keep advancing as I call push_back()). > > In other words, this assertion fails (but I expect it to succeed): > > circular_buffer<int> buf(8); > circular_buffer<int>::iterator a; > circular_buffer<int>::iterator b; > a = buf.begin(); > buf.push_back(1); > b = buf.begin(); > assert(a == b); // Fails!! > > Also, this code fails too (but I expect it to succeed): > > circular_buffer<int> buf(8); > circular_buffer<int>::iterator a; > circular_buffer<int>::iterator b; > a = buf.end(); > buf.push_back(1); > b = buf.end(); > assert(a != b); // Also fails! > > Below is a full example that you can compile and try out: > > #include <boost/circular_buffer.hpp> > #include <stdio.h> > > int > main () > { > typedef boost::circular_buffer<int> buf_type; > // Instead of "end" moving ahead, "begin" is moving backwards when // > // using "push_back". > { > buf_type buf1(1024); > buf_type::iterator a; > buf_type::iterator b; > a = buf1.end(); > buf1.push_back(1); > buf1.push_back(2); > b = buf1.end(); > printf ("%d\n", a == b); > // >>> > // got: 1 > // expected: 0 > printf ("%d, %d\n", a-buf1.begin(), b-buf1.begin()); > // >>> > // got: 2, 2 > // expected: 0, 2 > } > { > buf_type buf2(1024); > buf_type::iterator c; > buf_type::iterator d; > c = buf2.begin(); > buf2.push_back(1); > buf2.push_back(2); > d = buf2.begin(); > printf ("%d\n", c == d); > // >>> > // got: 0 > // expected: 1 > // (i.e. "begin()" is not still pointing to first item!! > // This is incorrect, isn't it?) > printf ("%d, %d\n", buf2.end()-c, buf2.end()-d); > // >>> > // got: 0, 2 > // expected: 2, 2 > } > return 0; > } > > > Thanks, > David > > > > >

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determining the number of collumns in a .csv file
by Sean Farrow 27 Jul '09

27 Jul '09

Hi: I am currently using the boost.spirit example to process a csv file. Rather than stuffing all values in to a vector as the example does what I'dx like to do is to determine how many columns exist and stuff all values in to a multi-dimensional array. What is the best way of doing this? Cheers Sean.

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