May 2007 - Boost-users - lists.boost.org

Pointer in function parameter?
by Meryl Silverburgh 08 May '07

08 May '07

Hi, I have a vector <A*> and I want to switch boost's ref count pointer like this: vector< boost::shared_ptr<A> > aVector; aFunc(aVector[0]) ; // just call a My question is should I change the function parameter of aFuncion from this: void aFunc(A* aPtr) { // access aPtr } to this: void aFunc(shared_ptr<A> aPtr) { // access aPtr } Thank you.

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Question about a vector of boost shared_ptr
by Meryl Silverburgh 08 May '07

08 May '07

If I have an attribute of a vector of boost shared_ptr in a class, like this: class A; class B { public : ~B() { ...} private: std::vector< boost::shared_ptr<A> > aVector; }; What do I need to do in the destructor of B so that all the memory used by a vector of shared_ptr of A ('aVector') will be freed correctly? Thank you.

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Boost 1.34.0 Beta released
by Thomas Witt 08 May '07

08 May '07

The first beta of what will become version 1.34.0 is now available from http://www.boost.org. New Libraries * Foreach Library: BOOST_FOREACH macro for easily iterating over the elements of a sequence, from Eric Niebler. * Statechart Library: Arbitrarily complex finite state machines can be implemented in easily readable and maintainable C++ code, from Andreas Huber. * TR1 Library: An implementation of the C++ Technical Report on Standard Library Extensions, from John Maddock. This library does not itself implement the TR1 components, rather it's a thin wrapper that will include your standard library's TR1 implementation (if it has one), otherwise it will include the Boost Library equivalents, and import them into namespace std::tr1. Highlights include: Reference Wrappers, Smart Pointers, result_of, Function Object Binders, Polymorphic function wrappers, Type Traits, Random Number Generators and Distributions, Tuples, Fixed Size Array, Hash Function Objects, Regular Expressions and Complex Number Additional Algorithms. * Typeof Library: Typeof operator emulation, from Arkadiy Vertleyb and Peder Holt. * Xpressive Library: Regular expressions that can be written as strings or as expression templates, and that can refer to each other and themselves recursively with the power of context-free grammars, from Eric Niebler. Updated Libraries * Assign Library: o Support for ptr_map<key,T> via the new function ptr_map_insert() o Support for initialization of Pointer Containers when the containers hold pointers to an abstract base class. * Date_time library: o Support for new US/Canada timezone rules and other bug fixes. See Change History for details. * Filesystem Library: Major upgrade in preparation for submission to the C++ Standards Committee for TR2. Changes include: o Internationalization, provided by class templates basic_path, basic_filesystem_error, basic_directory_iterator and basic_directory_entry. o Simplification of the path interface by eliminating special constructors to identify native formats. o Rationalization of predicate function design, including the addition of several new functions. o Clearer specification by reference to POSIX, the ISO/ IEEE Single Unix Standard, with provisions for Windows and other operating systems. o Preservation of existing user code whenever possible. o More efficient directory iteration. o Addition of a recursive directory iterator. * Function Library: Boost.Function now implements a small buffer optimization, which can drastically improve the performance when copying or constructing Boost.Function objects storing small function objects. For instance, bind(&X:foo, &x, _1, _2) requires no heap allocation when placed into a Boost.Function object. * Functional/Hash Library o Use declarations for standard classes, so that the library doesn't need to include all of their headers o Deprecated the <boost/functional/hash/*.hpp> headers. o Add support for the BOOST_HASH_NO_EXTENSIONS macro, which disables the extensions to TR1 o Minor improvements to the hash functions for floating point numbers. * Graph Library: o edmonds_maximum_cardinality_matching, from Aaron Windsor. o lengauer_tarjan_dominator_tree, from JongSoo Park. o compressed_sparse_row_graph, from Jeremiah Willcock and Douglas Gregor of Indiana University. o sorted_erdos_renyi_iterator, from Jeremiah Willcock of Indiana University. o biconnected_components now supports a visitor and named parameters, from Janusz Piwowarski. o adjacency_matrix now models the Bidirectional Graph concept. o dijkstra_shortest_paths now calls vis.initialize_vertex for each vertex during initialization. o Note: the name of the compiled library for the GraphViz reader has changed to boost_graph (from bgl-viz) to match Boost conventions. o See the complete revision history for more information. * MultiArray Library: Boost.MultiArray now by default provides range-checking for operator[]. Range checking can be disabled by defining the macro BOOST_DISABLE_ASSERTS before including multi_array.hpp. A bug in multi_array::resize() related to storage orders was fixed. * Multi-index Containers Library: o New random access indices. o Non key-based indices feature new rearrange facilities. o This version also includes a number of optimizations and usage improvements. For a complete list of changes, see the library release notes. * Optional Library: o boost::none_t and boost::none now added to Optional's documentation o Relational operators now directly support arguments of type 'T' and 'none_t' o operator->() now also works with reference types. o Helper functions make_optional(val), make_optional (cond,val) and get_optional_value_or(opt,alternative_value) added. o Constructor taking a boolean condition (as well as a value) added. o Member function get_value_or(alternative_value) added. o Incompatbility bug with mpl::apply<> fixed. o Converting assignment bug with uninitialized lvalues fixed. * Parameter Library: o Every ArgumentPack is now a valid MPL Forward Sequence. o Support for unnamed arguments (those whose keyword is deduced from their types) is added. o Support for named and unnamed template arguments is added. o New overload generation macros solve the forwarding problem directly. o See also the Python library changes, below. * Pointer Container Library: o Support for serialization via Boost.Serialization. o Exceptions can be disabled by defining the macro BOOST_PTR_CONTAINER_NO_EXCEPTIONS before including any header. This macro is defined by default if BOOST_NO_EXCEPTIONS is defined. o Additional std::auto_ptr<T> overloads added s.t. one can also pass std::auto_ptr<T> instead of only T* arguments to member functions. o transfer() now has weaker requirements s.t. one can transfer objects from ptr_container<Derived> to ptr_container<Base>, * Python Library: o Boost.Python now automatically appends C++ signatures to docstrings. The new docstring_options.hpp header is available to control the content of docstrings. o stl_input_iterator, for turning a Python iterable object into an STL input iterator, from Eric Niebler. o Support for void* conversions is added. o Integrated support for wrapping C++ functions built with the parameter library; keyword names are automatically known to docsstrings. * Signals Library: More improvements to signal invocation performance from Robert Zeh. * Smart Pointers Library: o Allocator support as proposed in N1851 (162 Kb PDF). o pointer_cast and pointer_to_other utilities to allow pointer-independent code, from Ion Gaztanaga. * String Algorithm Library: o lexicographical_compare o join o New comparison predicates is_less, is_not_greater. o Negative indexes support (like Perl) in various algorihtms (*_head/tail, *_nth). * Wave Library: o Wave now correctly recognizes pp-number tokens as mandated by the C++ Standard, which are converted to C++ tokens right before they are returned from the library. o Several new preprocessing hooks have been added. For a complete description please refer to the related documentation page: The Context Policy. o Shared library (dll) support has been added for the generated Wave libraries. o The overall error handling has been improved. It is now possible to recover and continue after an error or a warning was issued. o Support for optional comment and/or full whitespace preservation in the generated output stream has been added. o The Wave library now performs automatic include guard detection to avoid accessing header files more than once, if appropriate. o Full interactive mode has been added to the Wave tool. Now the Wave tool can be used just like Python or Perl for instance to interactively try out your BOOST_PP macros. Additionally it is now possible to load and save the current state of an interactive session (macro tables et.al.). o The overall performance has been improved by upto 40-60%, depending on the concrete files to process. o Support for new pragmas has been added allowing to control certain library features from inside the preprocessed sources (partial output redirection, control of generated whitespace and #line directives). o Optional support for #pragma message "..." has been added. o This version also includes a number of bug fixes and usage improvements. For a complete list of changes, see the libraries change log. Supported Compilers Boost is tested on a wide range of compilers and platforms. Since Boost libraries rely on modern C++ features not available in all compilers, not all Boost libraries will work with every compiler. The following compilers and platforms have been extensively tested with Boost, although many other compilers and platforms will work as well. For more information, see the regression test results. * Apple GCC 4.0.1 on Mac OS X. * Borland C++ 5.8.2 on Windows. * GNU C++ o 3.2.x., 3.3.x, 3.4.x, 4.0.x, 4.1.x on Linux o 4.1.x on Solaris o 3.4.x on Windows * HP aC++ A.06.14. * Intel C++ 9.1 on Windows, 9.0 on Linux. * Metrowerks CodeWarrior 9.4 on Windows. * Microsoft Visual C++ 6.0 (sp5, with and without STLport), 7.0, 7.1, 8.0. Note: Boost does not support the non-standard "Safe" C++ Library shipping with Visual C++ 8.0, which may result in many spurious warnings from Boost headers and other standards-conforming C++ code. To suppress these warnings, define the macro _SCL_SECURE_NO_DEPRECATE. * Sun Studio 11 on Solaris. Acknowledgements A great number of people contributed their time and expertise to make this release possible. Special thanks go to Vladimir Prus for making Boost.Build version 2 a reality, David Abrahams for authoring a new getting started guide and Greg D. for answering countless questions. -- Thomas Witt witt(a)acm.org

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Build/install problems: BOOST 1_34 using VS.net
by dhruva 07 May '07

07 May '07

Hi, I am building BOOST using VS.net as follows (build goes fine): on the command prompt: cmd>bjam --toolset=msvc cmd>bjam --toolset=msvc --prefix=e:\boost install The installed libraries have "vc" instead of "vc71". The auto_link.hpp tries to link to libraries with "vc71". Is this a known issue? I try to build using the --layout=system as: cmd>bjam --toolset=msvc --layout=system cmd>bjam --toolset=msvc --layout=system install The copied libraries have libname-mt.lib (ex: boost_thread-mt.lib). To link with non-versioned plain libraries, I define BOOST_AUTO_LINK_NOMANGLE in the user.hpp. This tries to link with libname.lib (ex: boost_thread.lib) and that file will not be there. Is there something else I need to do or is it a known problem with this BETA? with best regards, dhruva -- Dhruva Krishnamurthy Contents reflect my personal views only!

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[1.34] autolink doesn't work when not specifying toolset version
by Yuval Ronen 07 May '07

07 May '07

I downloaded 1.34.0 beta, compiled it using bjam --toolset=msvc --without-python stage then wrote a small program that uses Boost.Thread. It didn't link. The linker was looking for libboost_thread-vc80-mt-gd-1_34.lib, but couldn't find it. Rightfully enough, because there was no such file. The bjam command created libboost_thread-vc-mt-gd-1_34.lib - almost the same, just "vc" instead of "vc80". So I ran bjam again, this time with bjam --toolset=msvc-8.0 --without-python stage and then everything worked fine. This can a be a bug either in Boost.Build, or in the autolink feature, or in the documentation (getting_started.html) that suggests that specifying the toolset version is optional, or in my brain... Which is it?

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Comparing boost::function<void()>
by Rennie deGraaf 07 May '07

07 May '07

Hello, Could anyone please tell me why the following code fails to compile: > inline void rmfunc(std::list<boost::function<void()> >& funcs, boost::function<void()> f) > { > for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) > { > if (boost::function_equal(*i, *f)) > i = funcs.erase(i); > } > } while the following does compile: > template <typename T> > inline void rmfunc(std::list<boost::function<void()> >& funcs, const T& f) > { > for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) > { > if (boost::function_equal(*i, f)) > i = funcs.erase(i); > } > } and seemingly equivalent code, placed in-line in the calling function, also compiles? > for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) > { > if (boost::function_equal(*i, boost::ref(bar))) > i = funcs.erase(i); > } The full code for my test program (with the non-compiling function commented out) is attached. My compiler is gcc 4.1.1; I'm using the boost 1.33.1 package from Fedora Core 5. Thanks, Rennie deGraaf #include <list> #include <algorithm> #include <boost/ref.hpp> #include <boost/function.hpp> #include <iostream> struct Foo { void operator()() {} }; /*inline void rmfunc(std::list<boost::function<void()> >& funcs, boost::function<void()> f) { for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) { if (boost::function_equal(*i, f)) i = funcs.erase(i); } }*/ template <typename T> inline void rmfunc(std::list<boost::function<void()> >& funcs, const T& f) { for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) { if (boost::function_equal(*i, f)) i = funcs.erase(i); } } int main() { std::list<boost::function<void()> > funcs; Foo foo; Foo bar; funcs.push_back(boost::ref(foo)); funcs.push_back(boost::ref(bar)); std::cout << funcs.size() << std::endl; // should be 2 rmfunc(funcs, boost::ref(foo)); std::cout << funcs.size() << std::endl; // should be 1 for (std::list<boost::function<void()> >::iterator i=funcs.begin(); i!=funcs.end(); ++i) { if (boost::function_equal(*i, boost::ref(bar))) i = funcs.erase(i); } std::cout << funcs.size() << std::endl; // should be 0 return 0; }

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boost::bind, C++ member function and C callback function
by Li, PingShan (Kansas City) 07 May '07

07 May '07

I have a question related to setting a C++ member function as a callback function for C library's API. I searched the boost mailing list and Google, but I could not find a clear answer. The function I need to call is OpenSSL's CRYPTO_set_id_callback function. It accepts a function pointer as its parameter. The following code works fine: unsigned long IdCallBack( ) { return ( ( unsigned long )GetCurrentThreadId( ) ); } CRYPTO_set_id_callback( (unsigned long (*)())IdCallBack ); I have a C++ class and I want to set the call back function to be the member function of my class, I tried to use boost::bind: class Test { public: Test( unsigned long a ) : m_long( a ) { } virtual ~Test( ) { } unsigned long GetId() { return m_long; } void SetCallBack() { CRYPTO_set_id_callback( boost::bind( &Test::GetId, this ) ); } private: unsigned long m_long; }; I got the following error under VC++ 7.1: error C2664: 'CRYPTO_set_id_callback' : cannot convert parameter 1 from 'boost::_bi::bind_t<R,F,L>' to 'unsigned long (__cdecl *)(void)' with [ R=unsigned long, F=boost::_mfi::mf0<unsigned long,Test>, L=boost::_bi::list1<boost::_bi::list_av_1<Test *>::B1> ] No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called Is it possible to use boost::bind to bind a C++ member function as a callback function for C interface? Thank you

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[BoostCon07][testing] Session reminder.
by Rene Rivera 07 May '07

07 May '07

Boost Community, The Boost Conference will be here in very short order! And I need to get feedback for the "Testing Boost" sprint we'll be doing <http://boostcon.com/program/sessions#rivera-testing-sprint>. If you have any ideas, concerns, off the wall comments, etc. at *minimum* send them directly to me at "rrivera/acm.org". Why that account? Well because that will be the one account I can guarantee I will access to during the conference, and hence people can send me stuff up to the last minute. Not that I'm encouraging lateness, but I know how busy we all are ;-) If you are going to send it to the Boost dev list you will also want to eventually send me a summary follow up, if needed, from the ensuing discussions. Looking forward to seeing some of you at Aspen! -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com -- 102708583/icq - grafikrobot/aim - grafikrobot/yahoo

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Example of using a mutex a lock
by Stephen Torri 07 May '07

07 May '07

I am trying to create a class for performing log tracing. While my present program is single threaded as far as my code is concerned this may not always be the case. Below is the code that I am proposing to use. What I am weak on is concurrent programming. I know that I need to use a mutex but I am not sure how to use the boost thread mutex library and locks. Can someone comment on how I can modify the Trace_State class to use locking? Stephen ---------------- #include <boost/cstdint.hpp> #include <boost/shared_ptr.hpp> #include <fstream> #include <boost/date_time/posix_time/posix_time.hpp> #include <sstream> #include <boost/format.hpp> namespace libreverse { namespace trace { /* Idea taken from http://www.codeproject.com/debug/xytrace.asp * (28 Jan 2002 - Xiangyang Liu) * * I have modified this so that we don't use varargs and use constant types */ class TraceLevel { public: static boost::uint32_t TraceNone; // No trace static boost::uint32_t TraceError; // Only trace error static boost::uint32_t TraceInfo; // Some extra information static boost::uint32_t TraceDebug; // Debugging information static boost::uint32_t TraceDetail; // Detailed debugging information }; boost::uint32_t TraceLevel::TraceNone = 0; boost::uint32_t TraceLevel::TraceError = 10; boost::uint32_t TraceLevel::TraceInfo = 20; boost::uint32_t TraceLevel::TraceDebug = 30; boost::uint32_t TraceLevel::TraceDetail = 40; class Trace_State { public: typedef boost::shared_ptr<Trace_State> ptr_t; static Trace_State::ptr_t Instance() { // Lock the resource? if ( m_instance.get() == 0 ) { m_instance = Trace_State::ptr_t ( new Trace_State() ); } // Unlock the resource? return m_instance; } void set_Trace_File_Prefix ( std::string name ) { assert ( ! name.empty() ); // Lock the resource // Close the present file m_file_prefix = name; // Unlock the resource } void set_Trace_Level ( boost::uint32_t level ) { // Lock the resource // Change level m_trace_level = level; // Unlock the resource } void open_Trace_File ( void ) { // Create file name std::stringstream name; // Get current time boost::posix_time::ptime now = boost::posix_time::second_clock::local_time(); std::tm tm_ref = boost::posix_time::to_tm ( now ); boost::gregorian::date today = now.date(); name << boost::format ( "%s_%s_%02d:%02d:%02d.txt" ) % m_file_prefix % boost::gregorian::to_iso_extended_string ( today ) % tm_ref.tm_hour % tm_ref.tm_min % tm_ref.tm_sec; m_log_stream.open ( (name.str()).c_str() ); } void close_Trace_File ( void ) { m_log_stream.close(); } boost::uint32_t get_Trace_Level ( void ) const { boost::uint32_t level = 0; // Lock the resource // get the level level = m_trace_level; // unlock the resource // return the level return level; } void write_Message ( std::string msg ) { // Lock the resource // Write to the file m_log_stream << msg; // Unlock the resource } private: Trace_State() : m_file_prefix ( "Trace" ), m_trace_level ( TraceLevel::TraceNone ) {} static Trace_State::ptr_t m_instance; std::string m_file_prefix; boost::uint32_t m_trace_level; //boost::recursive_mutex m_mutex; std::ofstream m_log_stream; }; Trace_State::ptr_t Trace_State::m_instance; class Trace { public: static void write_Trace ( boost::uint32_t level, std::string message ) { Trace_State::ptr_t state_ptr = Trace_State::Instance(); // If the level is equal to or greater than the present // level we record out message. if ( level >= state_ptr->get_Trace_Level() ) { state_ptr->write_Message ( message ); } } }; } /* namespace trace */ } /* namespace trace */ int main (int, char**) { libreverse::trace::Trace_State::ptr_t state_ptr = libreverse::trace::Trace_State::Instance(); state_ptr->set_Trace_File_Prefix ("Funky"); state_ptr->open_Trace_File(); state_ptr->close_Trace_File(); return 0; }

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[serialization] throwing exceptions in load_construct_data
by Johan Råde 07 May '07

07 May '07

Hi Robert, A long time ago (in the fall of 2005 I think) I reported a bug to you: If you throw an exception in a load_construct_data function (before you have completed the construction of the object) then the serialization library crashes. It calls a destructor on the object that never was constructed. It seems this bug has not been fixed in 1.34 beta. Do you plan to fix this bug? --Johan

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