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size_type doubts / integer library..
by Zeljko Vrba 19 Aug '08

19 Aug '08

Integer types in C and C++ are a mess. For example, I have made a library where a task is identified by a unique unsigned integer. The extra information about the tasks is stored in a std::vector. When a new task is created, I use the size() method to get the next id, I assign it to the task and then push_back the (pointer to) task structure into the vector. Now, the task structure has also an "unsigned int id" field. In 64-bit mode, sizeof(unsigned) == 4, sizeof(std::vector::size_type) == 8 I get a warnings about type truncation, and obviously, I don't like them. But I like explicit casts and turning off warnings even less. No, I don't want to tie together size_type and task id type (unsigned int). One reason is "aesthetic", another reason is that I don't want the task id type to be larger than necessary (heck, even a 16-bit type would have been enough), because the task IDs will be copied verbatim into another std::vector<unsigned> for further processing (edge lists of a graph). Doubling the size of an integer type shall have bad effects on CPU caches, and I don't want to do it. What to do? Encapsulate into "get_next_id()" function? Have a custom size() function/macro that just casts the result of vector::size and returns it? == Another example: an external library defines its interfaces with signed integer types, I work with unsigned types (why? to avoid even more warnings when comparing task IDs with vector::size() result, as in assert(task->id < tasks.size()), which are abundant in my code). Again, some warnings are unavoidable. What to do to have "clean" code? == Does anyone know about an integer class that lets the user define the number of bits used for storage, lower allowed bound and upper allowed bound for the range? Like: template<int BITS, long low, long high> class Integer; BITS would be allowed to assume a value only equal to the one of the existing integer types (e.g. 8 for char, 16 for short, etc.), and the class would be constrained to hold values in range [low, high] (inclusive). All operations (+-*/<<>><>) would be compile-time checked to make sense. For example, it would be valid to add Integer<32, 0, 8> with Integer<8, 0, 8> and store into Integer<8, 0, 16> (or Integer<8, 0, 17>) result, but NOT into Integer<8, 0, 8> result. The operations would also be checked at run-time to not overflow. Address-of operator would convert to signed or unsigned underlying integer type, depending on the lower bound. Mixing operations with native integer types would be allowed, provided ranges are respected[*]. And, of course, the library should have a "production mode" where the class would turn off all checks. Does anybody know about such a library? Is a unified numeric tower too much to ask for, at least in the form of a library? How do you deal with these issues? [*] If there's no such library in existence, I might be willing to think about a set of "sane" axioms and checks for automatic conversions. And I have "Hacker's Delight" at home, so I can peek into it and get formulas for deriving bounds of arithmetic operations. And yes, is this even easily implementable within C++ template framework; one has to deal with integer overflow.. What happens in template<long A, long B> class blah { const long T = A+B; }; when A+B overflows? Compiler error? Undefined result? Did C++0x do anything to clean up the integer types mess? This is a proposal for extension to the C language: http://www.cert.org/archive/pdf/07tn027.pdf Anything similar available for C++? </rant> Or should I just listen to the devil on my shoulder and turn off the appropriate warnings?

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[Intrusive] compile error with codewarrior
by David Klein 19 Aug '08

19 Aug '08

hi all, i'm trying to use the intrusive library but can't compile anything. i also tried member_hook's and the slist instead of list but it fails with the same error. any ideas on how to fix this? #include <boost/intrusive/list.hpp> struct foo : public list_base_hook<> { }; void dummy( void ) { list<foo> l; } 1>..\..\include\boost\intrusive\list.hpp(1435): illegal non-type template argument 1>..\..\include\boost\intrusive\list.hpp(1435): (point of instantiation: 'dummy()') 1>..\..\include\boost\intrusive\list.hpp(1435): (instantiating: 'boost::intrusive::list<foo, boost::intrusive::none, boost::intrusive::none, boost::intrusive::none>') 1>..\..\include\boost\intrusive\list.hpp(1435): (instantiating: 'boost::intrusive::list_impl<boost::intrusive::listopt<boost::intrusive::detail::base_hook_traits<foo, boost::intrusive::list_node_traits<void *>, 1, boost::intrusive::default_tag, 1>, unsigned long, true>>') 1>..\..\include\boost\intrusive\list.hpp(1435): note: (corresponding point of instantiation for 'boost::intrusive::list_impl<boost::intrusive::listopt<boost::intrusive::detail::base_hook_traits<foo, boost::intrusive::list_node_traits<void *>, 1, boost::intrusive::default_tag, 1>, unsigned long, true>>') 1>..\src\main.cpp(15): note: (corresponding point of instantiation for 'boost::intrusive::list<foo, boost::intrusive::none, boost::intrusive::none, boost::intrusive::none>') compiler: metrowerks c/c++ for embedded arm version 3.0 build 138 (it's the compiler for the nintendo ds platform) boost version: 1.35 + 1.36 -- regards, dave

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Boost.Filesystem 1.36.0: Define BOOST_FILESYSTEM_NO_DEPRECATED no longer works
by Peter Klotz 19 Aug '08

19 Aug '08

#include <boost/filesystem/convenience.hpp> int main(void) { return 0; } When compiling the above code with gcc 4.1 and define BOOST_FILESYSTEM_NO_DEPRECATED I obtain these error messages: boost/filesystem/convenience.hpp: In function 'std::string boost::filesystem::extension(const boost::filesystem::path&)': boost/filesystem/convenience.hpp:98: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp: In function 'std::wstring boost::filesystem::extension(const boost::filesystem::wpath&)': boost/filesystem/convenience.hpp:100: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp: In function 'std::string boost::filesystem::basename(const boost::filesystem::path&)': boost/filesystem/convenience.hpp:103: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp: In function 'std::wstring boost::filesystem::basename(const boost::filesystem::wpath&)': boost/filesystem/convenience.hpp:105: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp: In function 'boost::filesystem::path boost::filesystem::change_extension(const boost::filesystem::path&, const std::string&)': boost/filesystem/convenience.hpp:108: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp:108: warning: left-hand operand of comma has no effect boost/filesystem/convenience.hpp: In function 'boost::filesystem::wpath boost::filesystem::change_extension(const boost::filesystem::wpath&, const std::wstring&)': boost/filesystem/convenience.hpp:110: error: expected primary-expression before '>' token boost/filesystem/convenience.hpp:110: warning: left-hand operand of comma has no effect boost/system/error_code.hpp: At global scope: It works, when compiled without BOOST_FILESYSTEM_NO_DEPRECATED. The problem seems to be a new #ifndef in convenience.hpp that did not exist in 1.35.0. Regards, Peter. Peter Klotz Software Engineer Phone: +43 (0) 50 8648-4100 Fax: +43 (0) 50 8648-4111 E-Mail: peter.klotz(a)ith-icoserve.com ---------------------------------------------------------------- ITH icoserve technology for healthcare GmbH A-6020 Innsbruck, Innrain 98 www.ith-icoserve.com Rechtsform: Gesellschaft mit beschränkter Haftung Firmensitz: 6020 Innsbruck, Innrain 98 Firmenbuchnummer: FN 174117f Firmenbuchgericht: Innsbruck DVR: 0983039

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Re: [Boost-users] size_type doubts / integer library..
by Lang Stefan 19 Aug '08

19 Aug '08

-----Ursprüngliche Nachricht----- On Mon, Aug 18, 2008 at 12:06:08PM +0200, Lang Stefan wrote: > > > A) you intend to use your ID to later reference some address or offset > > (which is the same) in memory. If that is your intention, then you > > should stick to the size type (i. e. std:size_t). Problem solved. > > > Yes, it is used as an index into a vector. And that's what I did (typedef vector<..>::size_type pin_id). Well, then why don't you simply use std::size_t ? Yes, it's unsigned, and I agree with you it's not perfect (see below). But it will immediately rid you of all those nasty conversion warnings! > Hm, do they? Correct me if I'm wrong, but I don't think that C++ mandates flat address space -- it just > requires that each individual object has a contiguous memory representation. And there can be discrepancy > between the two, e.g. 80286 protected mode: largest segment size is 64k, yet the largest amount of > addressable memory is 16MB (or even in the range of TB if one allocates all LDTs and plays with swapping). Bugger, you're right, didn't think of that. > So, size_type should be able to represent the size of a *single* largest representable object. Why use it > for e.g. number of elements in a vector? That is something I did give some thought about in the past, to the point where I considered implementing my own set of container classes! However, I realized that in a sense, 'size_type' is indeed the correct type for an index. The reason behind it is this: an index type needs to be able to address a range of values that spans the minimum (0) and maximum (?) possible index for a container of some arbitrary type. For the STL, the smallest entity you can put inside a container is a single byte (disregarding bit-arrays). And the maximum number of such entities a container could legally contain would be limited by the amount of memory available divided by the size of the contained elements. While, as you pointed out, there doesn't need to be a direct relation from index to memory address, the range an index type needs to cover is equal to the range a 'size_type' needs to cover. Moreover, at least on a small scope, every architecture I am aware of groups values of container elements into one or more chunks of memory, which in turn store adjacent values into adjacent memory slots. So at least on a local scale, index values do correspond to memory addresses or memory offsets. > The "problem" could be solved by using largest _signed_ type both for size_type and difference_type. [snip] > So I'd advocate signed representation for size_type and difference_type. I agree. Stefan

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program_options does not compile
by dejfson 19 Aug '08

19 Aug '08

Dear All, if I try this piece of code: ---------------------------------------------- --------------------------------------------- extern "C" { #include <vmeapi.h> } #include <iostream> #include <signal.h> #include <string> #include <boost/program_options.hpp> // FANCY THINGY HERE: IF YOU INCLUDE CURSES BEFORE STRING, IT WILL BREAK COMPILATION #include <curses.h> //using namespace std; //namespace po = boost::program_options; static void sig_catch(int sig) { VME_Release(); /* Exception handler */ switch(sig) { case SIGINT : case SIGTERM : // nl(); // echo(); cout << "\nVME safe exit." << endl; VME_Release(); if (VME_IsErr()) { cout << "Errors at VME_Release():" << endl; VME_DispErr(); } exit(0); break; default : break; } } int main (int argc, char **argv) { /* Init VME access */ VME_Init(); if (VME_IsErr()) { VME_DispErr(); cout << "^C to quit." << endl;; } /* Turn off auto error reporting */ VME_ErrQuiet(); /* Install signal handler */ if (signal(SIGINT, &sig_catch) == (void *) -1) cout << "VMET Can't install SIGINT handler." << endl; if (signal(SIGTERM, &sig_catch) == (void *) -1) cout << "VMET Can't install SIGTERM handler." << endl; cout << "works somehow" << endl; VME_Release(); if (VME_IsErr()) VME_DispErr(); } ---------------------------------------------------------- ---------------------------------------------------------- it does not compile. Compilator identifies the problem as: g++ -pipe -fcommon -I/acc/local/ppc4/include -D__NO_INCLUDE_WARN__ -I/user/biswop/include -I./include -c main.cpp -o main.ppc4.o In file included from /acc/local/ppc4/include/boost/program_options.hpp:15, from main.cpp:8: /acc/local/ppc4/include/boost/program_options/parsers.hpp:156: parse error before `>' make: *** [main.ppc4.o] Error 1 ------------------------------------------------------------ By looking on the code in parsers.hpp I do not see any particular breaks, thus I suspect that there is something very odd with compiler. This piece of code is used on PPC processors in VME industrial crates. The operating system is LynxOS, however it uses quite old version of compiler - 2.95.3. I do not have any chance how to upgrade it as we use this compiler everywhere. Boost version is 1.33.1 (and again no chance to upgrade, however in this respect I could very probably force cross-compiler to compile the library) I would appreciate any info/hint how to make it running by using this compiler. Thanks a lot d.

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How to transform a single-threaded program into a multi-threaded program? (Source example)
by Stephen Torri 18 Aug '08

18 Aug '08

What I am trying to learn how to do is convert a single threaded program into a multi-threaded program. The task of the program is to analyze a text file a set number of times. Each analysis of the text file does not depend on another. The only thing that they need is the name of the file, how many iterations of the analysis to do and a unique id. I am not concerned about the information from each round being printed in sequential order. That is for example if thread A has a unique ID of 50 and thread B has a unique ID of 51 that I want thread B's output ahead of thread A's output. The output is going to be captured into a file and post-processed in a spreadsheet application. Below is a running example of what I am trying to do. To restate my question: How do I use boost threads to make a multi-threaded version of this program? Stephen ----- EXAMPLE CODE ----- #include <boost/bind.hpp> #include <boost/cstdint.hpp> #include <boost/format.hpp> #include <boost/program_options.hpp> #include <boost/shared_ptr.hpp> #include <boost/thread/thread.hpp> #include <iostream> #include <string> #include <sstream> class Work { public: std::string process ( boost::uint32_t round_number, boost::uint32_t iterations, std::string file ) { // Read file for data std::stringstream result; for ( boost::uint32_t index = 0; index != iterations; ++index ) { // Perform algorithm and save best result result << boost::format ("%1%:%2%") % round_number % index << std::endl; } return result.str(); } }; int main (int argc, char** argv) { boost::program_options::options_description generic ( "Generic options" ); generic.add_options() ( "help", "produce help message" ) ( "file", boost::program_options::value<std::string>(), "Target file" ) ( "rounds", boost::program_options::value<boost::uint32_t>(), "Number of rounds (default: 1)" ) ( "iterations", boost::program_options::value<boost::uint32_t>(), "Number of iterations (default: 5)" ); boost::program_options::variables_map vm; boost::program_options::store ( boost::program_options::command_line_parser ( argc, argv ). options(generic).run(), vm ); boost::program_options::notify ( vm ); if ( vm.count ( "help" ) ) { std::cout << generic << std::endl; return 0; } // Get values from command flags boost::uint32_t m_rounds = 1; boost::uint32_t m_iterations = 5; if ( vm.count ( "rounds" ) ) { m_rounds = vm["rounds"].as<boost::uint32_t>(); if ( m_rounds == 0 ) { std::cout << " Invalid number of rounds: 0" << std::endl; return 0; } } if ( vm.count ( "iterations" ) ) { m_iterations = vm["iterations"].as<boost::uint32_t>(); if ( m_iterations == 0 ) { std::cout << " Invalid number of iterations: 0" << std::endl; return 0; } } std::cout << "Number of rounds: " << m_rounds << std::endl; std::cout << "Number of iterations: " << m_iterations << std::endl; boost::shared_ptr<Work> data_alg_ptr ( new Work() ); for ( boost::uint32_t index = 0; index < m_rounds; ++index ) { std::cout << data_alg_ptr->process ( index, m_iterations, "data.txt" ) << std::endl; } return 0; }

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Re: [Boost-users] [swap] How to override swap now?
by Joseph Gauterin 18 Aug '08

18 Aug '08

Hi Terry, >How should a user/developer like me implement a custom swap so that users >get the benefit of my::swap, then boost::swap, and finally std::swap without >putting too much burden on my user. In the same way that swap functions are currently provided: either a specilization of std::swap or a 'swap' function in the same namespace as a UDT. >If the user does this... >using namespace std; >using namespace boost; >using namespace my; >And then somewhere in his code... > HisType a = MakeA(); > HisType b = MakeB(); > swap(a, b); // Unqualified? Or should the user specify a namespace? > Which one? A call to std::swap will swap the two values using temporary values and assignments. A call to boost::swap will call my::swap using argument dependent lookup. A call to my::swap will just call my::swap. An unqualified call to swap will call my::swap using argument dependent lookup. >If the user has his own swap(HisType, HisType) invoke that. >Otherwise, if HisType.swap() exists, then use that. >Otherwise, use my::swap() if its "better" than boost::swap >Otherwise, use boost::swap(), if its "better" than std::swap >Otherwise, just use std::swap(). boost::swap calls my::swap() if it exists, else it calls std::swap(). HisType.swap is not considered directly. >Sorry about all the ambiguity. But that's the real problem, isn't it? Indeed - but we're using a trick to make sure that boost::swap is never ambiguous with std::swap. So: using namespace std; using namespace boost; swap(a, b); Will call a function called swap in the namespace where 'a' is declared if it exists (adl), or std::swap otherwise. It will never call boost::swap. std::swap(a, b); Will swap 'a' and 'b' using temporaries and assignments. boost::swap(a, b); Will call a function called swap in the namespace where 'a' is declared if it exists, or std::swap otherwise. No 'using' statements or declarations are required. Joe.

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[Function] Comparing function objects with std::find
by Christian Larsen 18 Aug '08

18 Aug '08

Hi, I'm storing function objects in a std::vector, but to remove one again, I need to find an iterator to the one I want to remove. I do this in an "unregister" function taking a single boost::function<void ()> as parameter. Inside the function I would like to use the std::find algorithm to get an iterator to that function in the vector. I'm getting compile errors, though; see the example below. How do I fix these? I'm using MSVC++ 8 (SP1), and Boost 1.33.1 (can not upgrade). Example, where in my "unregister" function I use find as in the last part of this example (i.e. I have a Listener and not a plain function pointer). This does not compile: #include <algorithm> #include <vector> #include <boost/function.hpp> using namespace std; using namespace boost; void listenerA() {} void listenerB() {} int main() { typedef function<void ()> Listener; typedef vector<Listener> ListenerVector; ListenerVector listeners; listeners.push_back(&listenerA); listeners.push_back(&listenerB); ListenerVector::iterator iter; // This compiles and works iter = find( listeners.begin(), listeners.end(), &listenerB); assert(iter != listeners.end()); // This gives: // error C2666: 'boost::operator ==' : 4 overloads have // similar conversions iter = find( listeners.begin(), listeners.end(), Listener(&listenerB)); assert(iter != listeners.end()); return 0; } Compiler errors: c:\program files (x86)\microsoft visual studio 8\vc\include\algorithm(40) : error C2666: 'boost::operator ==' : 4 overloads have similar conversions d:\development\boost_1_33_1\boost\function\function_template.hpp(583): could be 'void boost::operator ==<R,Allocator>(const boost::function0<R,Allocator> &,const boost::function0<R,Allocator> &)' [found using argument-dependent lookup] with [ R=void, Allocator=std::allocator<void> ] d:\development\boost_1_33_1\boost\function\function_base.hpp(609): or 'bool boost::operator ==<boost::function<Signature>>(Functor,const boost::function_base &)' [found using argument-dependent lookup] with [ Signature=void (void), Functor=boost::function<void (void)> ] d:\development\boost_1_33_1\boost\function\function_base.hpp(600): or 'bool boost::operator ==<_Ty>(const boost::function_base &,Functor)' [found using argument-dependent lookup] with [ _Ty=boost::function<void (void)>, Functor=boost::function<void (void)> ] or 'built-in C++ operator==(void (__thiscall boost::function0<R,Allocator>::dummy::* )(void), void (__thiscall boost::function0<R,Allocator>::dummy::* )(void))' with [ R=void, Allocator=std::allocator<void> ] while trying to match the argument list '(boost::function<Signature>, const boost::function<Signature>)' with [ Signature=void (void) ] c:\program files (x86)\microsoft visual studio 8\vc\include\algorithm(74) : see reference to function template instantiation '_InIt std::_Find<std::_Vector_iterator<_Ty,_Alloc>,_Ty>(_InIt,_InIt,const _Ty &)' being compiled with [ _InIt=std::_Vector_iterator<Listener,std::allocator<Listener>>, _Ty=Listener, _Alloc=std::allocator<Listener> ] d:\development\misc\functionvector\functionvector.cpp(35) : see reference to function template instantiation '_InIt std::find<std::_Vector_iterator<_Ty,_Alloc>,boost::function<Signature>>(_InIt,_InIt,const _Ty &)' being compiled with [ _InIt=std::_Vector_iterator<Listener,std::allocator<Listener>>, _Ty=Listener, _Alloc=std::allocator<Listener>, Signature=void (void) ] Best regards, Christian

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Boost.Time_series library
by Kim Tang 18 Aug '08

18 Aug '08

Hi all, i ve downloaded the time_series.zip by the link: http://boost-consulting.com/vault/index.php?directory=Math%20-%20Numerics and unzip it on my computer. But the compilation of the example (time_series\time_series\main.cpp) program fails due to the errors: c:\boost\time_series\boost\sequence\size.hpp(27) : error C2143: syntax error : missing ';' before '<' 1> c:\boost\time_series\boost\sequence\size.hpp(33) : see reference to class template instantiation 'boost::sequence::impl::size<S,T>' being compiled 1>c:\boost\time_series\boost\sequence\size.hpp(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\boost\time_series\boost\sequence\size.hpp(27) : error C2238: unexpected token(s) preceding ';' 1>c:\boost\time_series\boost\sequence\size.hpp(29) : error C2143: syntax error : missing ';' before '(' 1>c:\boost\time_series\boost\sequence\size.hpp(29) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\boost\time_series\boost\sequence\size.hpp(30) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int After looking at the file boost\time_series\boost\sequence\size.hpp i see that the variable name range_size in line 27 is unknown. So my question is which file should i include? I ve searched for the variable name range_size in the time_series folder. And one possibility is the file boost\detail\range_concepts.hpp. But is this the right file? Thanks, Kim Tang

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shared_ptr custom deallocator - member function?
by Alejandro Martinez 18 Aug '08

18 Aug '08

can i use some class's (a kind of factory) member be used as a deallocator in a shared_ptr? like to do something like this: boost::shared_ptr<mysqlpp::Connection> cp(sDbPool->grab(), boost::bind(&mysqlpp::ConnectionPool::release, sDbPool)); where sDbPool is a shared_ptr to the "factory/pool manager". i tryed just that, but visual studio express 2008 keeps crashin on me. (the compiler crashes, not the program). any ideas?

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