- Boost-users - lists.boost.org

scoped_ptr faq
by Bruno Martínez 28 Nov '05

28 Nov '05

Hi. I had the same question that is answered there, but the answer didn't fit my problem. I'm using scoped_ptr<node> inside node itself, so node is incomplete at the point of use. That forbids using auto_ptr, IIUC. I think it would be good to add to the answer: Q. Why doesn't scoped_ptr have a release() member? A. When reading source code, it is valuable to be able to draw conclusions about program behavior based on the types being used. If scoped_ptr had a release() member, it would become possible to transfer ownership of the held pointer, weakening its role as a way of limiting resource lifetime to a given context. Use std::auto_ptr where transfer of ownership is required, or shared_ptr if incomplete type support is needed. "or shared_ptr if incomplete type support is needed." is mine. How's that? Regards, Bruno

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How to compile boost in Borland c++ Builder 6
by pes nemarn 28 Nov '05

28 Nov '05

As subject says - I am in need of information about on how to compile boost in Borland c++ Builder 6 on operation system Windows XP. I have been searching everywhere, instructions are either too complicated or badly written - in any case I still havent found the answer. I hope you'll help me, I'm realy stuck and you guys are probably my last resort. Looking forward to answers or hints, cheers.

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serialization: handling variable length data
by __PPS__ 27 Nov '05

27 Nov '05

in simplest case std::string is serialized this way: length|string data. in this case it's possible to feed invalid data to deserialization function so that application stalls waiting for the os to reserve huge pile or ram, or fails with bad alloc. this invalid data could be intentionally manually edited or as well it could be the case where you serialize ints and then try to deserialize data as strings (or whatever else). isn't it possible to have archives such check somehow the size of available stream data. (eg, for stringstream), or archives that initialized with a data pointer and the size of the data pointed by that pointer or maybe something else here's a complete example that shows such problem in action ///////////////////////////// #include <iostream> #include <fstream> #include <string> #include <ctime> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/binary_iarchive.hpp> #include <boost/serialization/serialization.hpp> using namespace std; using namespace boost::archive; int main()try{ string s1 = "Hello world!", s2; { ofstream file("data.txt", ios::binary | ios::trunc); text_oarchive a(file, no_header); a << s1; } time_t t(time(0)); { ifstream file("data.txt", ios::binary); binary_iarchive a(file, no_header); a >> s2; } cout << "time elapsed: " << (time(0)-t) << "s" << endl; cout << "s2.size() => " << s2.size() << "\n" "s2 => \"" << s2.substr(0,64) << "...\"" << endl; }catch(const exception &e){ cout << "error: " << e.what() << endl; } ///////////////////////////// and the output I got on win xp: time elapsed: 110s s2.size() => 1210069553 s2 => "ello world! ..."

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Re: [Boost-users] program_options: wild write
by Merrill Cornish 27 Nov '05

27 Nov '05

Peter, Once I understood that even though positional parameters have been declared, they still have to be listed as an option, I got my positional parameter to work. I've even been able to follow the examples to "hide" the positional parameter name from the --help print out. I've still got the problem that an illegal option value triggers Dr Watson. I need to create a short example that I can post. Merrill

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How to sort a vector of tuples
by Sumanth J.V 26 Nov '05

26 Nov '05

Greetings, I have no idea why the following code does not work. Seems to work fine when I try sorting a vector of ints instead. I have even overloaded the < operator. If I understand correctly, this is the only requirement to sort a userdefined class. The compiler gets mad and spits out a a whole bunch of errors. thanx #include "boost/tuple/tuple_io.hpp" #include <vector> #include <algorithm> typedef boost::tuple<unsigned long int, unsigned long int, double, unsigned long int> Task; typedef std::vector<Task> TaskSet; bool operator<(const Task& a, const Task& b) { return boost::get<1>(a) < boost::get<1>(b); } int main(int argc, char** argv) { TaskSet ts; ts.push_back( boost::make_tuple(0, 0, 0, 0) ); ts.push_back( boost::make_tuple(3, 3, 3, 3) ); ts.push_back( boost::make_tuple(2, 2, 2, 2) ); std::sort(ts.begin(), ts.end()); return 0; }

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Re: [Boost-users] shared_ptr vs ordinary pointers
by Merrill Cornish 26 Nov '05

26 Nov '05

Jonathan, Yes, I should have left out the delete() for the shared_ptr version since that's one if its big features. I have used shared_ptr code similar to your example, but I can't use it in the case I'm thinking of. This particular pointer needs to be passed around so a single scope doesn't work. Thanks, Merrill

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shared_ptr vs ordinary pointers
by Merrill Cornish 26 Nov '05

26 Nov '05

With an ordinary C++ pointer, if I have a BaseClass and a DerivedClass derived from BaseClass, then I can do BaseClass* objectPtr; objectPtr = new DerivedClass(); Later, if BaseClass has a virtual destructor, I can call delete(objectPtr) and the DerivedClass destructor will be called. Now, does this work with shared_ptr? shared_ptr<BaseClass> objectPtr; objectPtr = shared_ptr<DerivedClass>(new DerivedClass()); and later, delete(objectPtr). Does any of the magic going on behind the scenes prevent shared_ptrs from being used like this? Merrill

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Re: [Boost-users] program_options: Failure Demo
by Merrill Cornish 25 Nov '05

25 Nov '05

Volodya, Should I post the ZIPs on boot-users or send it directly to you? Merrill

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Re: [Boost-users] program_options: Failure Demo
by Merrill Cornish 25 Nov '05

25 Nov '05

Volodya, I'm running Boost 1.33.0 compiled for MinGW multi-threaded. I agree that the message with only hex addesses isn't very useful, but that is all that pops up. ZoneAlert *says* the program is DWWIN.EXE, but I don't *see* Dr Watson. I disabled ZoneAlert and ran it again. I now have a 13KB Dr Watson log and a 3KB user.dmp file. Together, they ZIP to 4.8KB. Would you like me to send the ZIP to you? I have relinked the failing executable to remove unreferenced static libraries. It zips to 436KB. Would that be of any use to you? Merrill

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Question about boost::filesystem::path
by Stewart Tootill 25 Nov '05

25 Nov '05

I've just run into an interesting problem with boost::filesystem::path and thought I would raise it somewhere. When I run the following code, compiled with MSVC7.1, on windows XP I get an exception thrown when calling some_path_function. The exception is causes by boost::filesystem::path's implicit conversion constructor constructing a path from a string using the posix path matching rules. Obviously I can correct the problem by always using the native path checker argument, and that is fine, but the fact that this is an implicit conversion makes it hard to spot and I (and my colleagues) are not always that awake :). So I suppose the question is a) can the default path checking function be changed in such a way that on windows platforms it validates the path using windows rules and on posix platforms using posix rules, or b) should the constructor at fault here be made explicit since it can really catch you out. #include <boost/filesystem/path.hpp> #include <boost/filesystem/exception.hpp> #include <iostream> #include <string> void some_path_function( const boost::filesystem::path& path ) { std::cout << "Got a path : " << path.native_file_string() << std::endl; } int main() { try { std::string winPath = "c:\\windows\\system32\\kernel32.dll"; some_path_function( winPath ); } catch ( boost::filesystem::filesystem_error& err ) { std::cerr << "An error occured : " << err.what() << std::endl; } return 0; } Stewart Tootill Senior Engineer [Digital Text] Tel: +44 118 984 2151 - Fax: +44 118 984 3939 mailto:stewart.tootill@softel.co.uk www.softel.co.uk ________________________________________________________________________ This e-mail has been scanned for viruses by MessageLabs.

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