- Boost-users - lists.boost.org

Re: [Boost-users] program_options: wild write
by Merrill Cornish 22 Nov '05

22 Nov '05

Pedro, graph_file is a positional parameter. So should it be added to the option_description list? By the way, in one run in which I provided one positional parameter on the command line, the code then recognized graph_file; but claimed it was an unknown option. [sigh...] Merrill

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serialization: efficient binary archive
by __PPS__ 22 Nov '05

22 Nov '05

Hello, I want to write simple binary searialization class. the serialized data should be as compact as possible, e.g. I don't want to have "serialization::archive" string etc, since most of the time I need really basic serialization performed into many separate archives: something like hunrdreds of archives that contain simple int, or string. I also don't need any versioning. These data serializations are for a short period of time (automatically removed after a few minutes), to share data between multiple processes on the same machine. Basicly, I need to serialize many key-value pairs, and then to be able to extract values by their keys. Keys are simple strings, values can be anything. Since I cannot use boost::any for value part, then I decided to go a way around. I'll have a map that maps string keys to the serialized binary string of value, and then this big map is serialized. The other process then deserializes this map and if it accesses some value it also needs to deserialize the value. I really need simple searialization, something like i:1234,s[5]:Hello for int(1234) and string("Hello") with all the numbers serialized in binary etc, without any BE/LE code - always the same machine used. I think it would be really enough for me to have serialization of numbers, strings and binary data, but I want to use boost::serialization to allow users to insert objects of their own classes in that key-value pairs. basicly, my goal is to create such class that maps string keys to any data, then all this map is serialized and some other process deserializes this map and accesses values by keys. Is there's something in serialization library you could suggest me to look at. I viewed demo_fast_archive, but I cannot find good info on creating my own archive classes. It seems that my problem would be completely solved if there were some way to serialize boost::any, in this case I would only needed to serialize std::map<std::string,boost::any> thanks

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program_options: wild write
by Merrill Cornish 22 Nov '05

22 Nov '05

I'm making progess on using program_options. Using std::exception& gave me the real error message; but problems still remain. po::options_description desc("Options"); desc.add_options() ("help,h", " Display this help message.") ("version", " Display the version... .") ("limit", po::value<unsigned int>()->default_value(1), " This is the concurrency limit ...") ); // specify the single, required graph file positional parameter po::positional_options_description pd; pd.add("graph_file", 1); po::variables_map vm; po::store(po::command_line_parser(argc, argv). options(desc). positional(pd).run(), vm); po::notify(vm); //... code that references vm... I still can't get the positional parameter, but I've got other problem to research first. The options_descriptions above defines --limit as an unsigned integer with a default value of 1. It does get a default value of 1, and it will let you specify another unsigned integer value. But if you specify a non-unisgned integer (e.g., --limit=xxx or --limit=-5), then it bypasses the exception handling and calls Dr. Watson. The reported error is a wild write to unwritable memory. Any ideas how to chase this problem? Merrill

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[serialization] trouble with member_saver / member_save ?
by William Kemper 22 Nov '05

22 Nov '05

In 1.33.0 split_member uses: template<class Archive, class T> struct member_saver { static void invoke( Archive & ar, const T & t, const unsigned int file_version ){ access::member_save(ar, t, file_version); } }; And member_save looks like: template<class Archive, class T> static void member_save( Archive & ar, //const T & t, T & t, const unsigned int file_version ){ t.save(ar, file_version); } So the compiler complains about converting a const T to a non const T. It's curious that the source has the const T& in member_save commented out. Is there a workaround for this? Or is it planned to be fixed in the next release?

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Re: [Boost-users] lambda and shared_ptr?
by Mark Santaniello (AMD) 22 Nov '05

22 Nov '05

> > template< typename T > > > boost::function<T(T)> foo( T n_ ) > > { > > //Works, but leaks n > > //T *n = new T( n_ ); > > > > //Doesn't work > > boost::shared_ptr<T> n( new T(n_) ); > > > > return ( *n += _1 ); > > I think that you need to wrap n in boost::lambda::constant: > > return *constant(n) += _1; > > Without it, *n is evaluated immediately. > > > } > Peter, Thanks for the reply. I must be doing something dumb, because now I'm getting a build error. I think this *might* be the important part: /usr/include/boost/detail/is_incrementable.hpp:59: error: no match for 'operator++' in '++boost::detail::is_incrementable_::impl<boost::shared_ptr<int> >::x' The 799B source file is here: http://mark.santaniello.net/files/hof2.cpp The 19KB error message is here: http://mark.santaniello.net/files/err.txt :) -Mark

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The fate of has_member?
by Sniv Le Flomp 22 Nov '05

22 Nov '05

Hi, What ever happened with has_member? I really need it. - Sniv

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Re: [Boost-users] program_options: wild write
by Merrill Cornish 22 Nov '05

22 Nov '05

Christian, If I put an unknown --option on the command line, I get an exception with an "unknown option" message, just as you would expect. If I omit --limit from the command line, then it gets defaulted to 1, just as it should. However, if I put --limit on the command line with an illegal value, say a string or a negative number rather than an unsigned int, then there is no exception message, even though I am catching std::exception& and (...) and printing a message for both. Instead, Dr Watson is called, apparently without triggering a C++ exception. Merrill

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lambda and shared_ptr?
by Mark Santaniello (AMD) 22 Nov '05

22 Nov '05

All, I'm trying to use lambda and shared_ptr together, but I'm running into a problem. Please see the code below. I'd like the lambda-generated functor to hold the shared_ptr by value, such that its ref count is incremented. This doesn't seem to be happening. Instead, the shared_ptr is deleted when foo() returns, resulting in undefined behavior. What am I doing wrong? Thanks, Mark #include <boost/lambda/lambda.hpp> #include <boost/function.hpp> #include <boost/shared_ptr.hpp> #include <iostream> using namespace std; using namespace boost::lambda; template< typename T > boost::function<T(T)> foo( T n_ ) { //Works, but leaks n //T *n = new T( n_ ); //Doesn't work boost::shared_ptr<T> n( new T(n_) ); return ( *n += _1 ); } int main() { // start with one boost::function<int(int)> accum = foo(1); cout << accum(2) << endl; cout << accum(10) << endl; // start with zero boost::function<int(int)> accum2 = foo(0); cout << accum2(6) << endl; cout << accum2(2) << endl; }

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Re: [Boost-users] Collections of shared_ptr<Base> and shared_ptr<Derived>
by Keith Weintraub 21 Nov '05

21 Nov '05

Folks, I have come up with the following solution in template form. I would be ecstatic to receive any feedback on either my solution or original question. I am not an expert in these things and I can use all the help any generous soul could provide. Here is my solution: // Function template to create a vector<shared_ptr<Base> >* from // a vector<shared_ptr<Derived> > template<typename Base, typename Derived> vector<shared_ptr<Base> > *derivedSharedPtrVectorToBase(vector<shared_ptr<Derived> > const &dVec) { vector<shared_ptr<Base> > *bVec = new vector<shared_ptr<Base> >(dVec.size()); for(int i = 0; i < dVec.size(); i++) (*bVec)[i] = dVec[i]; return(bVec); } Thanks for your time, KW ________________________________ From: Keith Weintraub Sent: Wednesday, November 16, 2005 10:17 AM To: 'boost-users(a)lists.boost.org' Subject: Collections of shared_ptr<Base> and shared_ptr<Derived> Folks, What is the best way to pass a std::vector<boost::shared_ptr<Derived> > to a function that expects a std::vector<boost::shared_ptr<Base> >? Can I use a cast or should I create a new std::vector<boost::shared_ptr<Base> > by iterating over the std::vector<boost::shared_ptr<Derived> >? Here is some sample code. What f is doing is not important it is just an example: class A { // This class is from a library I have no control over. public: virtual string getName() { return string("A");} }; class B : public A { // I need to create B from A to have extra functionality public: virtual string getName() { return string("B");} virtual string getLongName() { return string("This is B");} }; void f(std::vector<boost::shared_ptr<A> > &v) { // This function is from a library that I have no control over. for(int i = 0; i < v.size(); i++) cout << v[i]->getName(); } int main(char *argv, int arc) { std::vector<boost::shared_ptr<B> > bvec(10); boost::shared_ptr<B> bPtr(new B); bvec[0] = bPtr; f(bvec); // This should not compile. <------------------------- } The last line (with the arrow) won't compile because std::vector<boost::shared_ptr<B> > cannot be converted to std::vector<boost::shared_ptr<A> >.

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[BGL, Graph] add_vertex with specific ctor
by Johan Oudinet 21 Nov '05

21 Nov '05

Hello, I like the named parameter method to define graph properties, so all our properties are concentrated in a struct. But, I'd like add a vertex with specific properties are already defined: //======================= #include <iostream> #include <string> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> using namespace std; using namespace boost; struct People { People () { } People (string const& n, int a) : name(n), age(a) { } string name; int age; }; int main(int, char**) { typedef adjacency_list< vecS, vecS, bidirectionalS, People > Graph; typedef graph_traits< Graph >::vertex_descriptor vertex_descriptor; Graph g; vertex_descriptor v; People n ("toto", 26); v = add_vertex (g); // this use the default ctor of People, a add_vertex(g, n) g[v] = n; // will be more efficiently (avoid a People assignment) cout << g[v].name << " is " << g[v].age << " old." << endl; } //======================= -- Johan

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