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Correct way to handle error in boost::filesystem::recursive_directory_iterator::increment()?
by Dominique Pellé 23 Jan '21

23 Jan '21

Hi I see code like this in an application to iterate over files in a directory with boost::filesystem (v1.70) without using exceptions: boost::filesystem::path dir("somedir"); boost::system::error_code error; boost::filesystem::directory_iterator node(dir, error), end; if (error) { return ...; } for (; node != end; node.increment(error)) { const boost::filesystem::path& path = node->path(); // ... } It appears to work... or mostly work since a crash was reported and the stack points to this area of the code. It's a rare crash that I could not reproduce myself. I suspect that there is a bug in the above code and it should instead be: boost::filesystem::path dir("somedir"); boost::system::error_code error; boost::filesystem::directory_iterator node(dir, error), end; for (; !error && node != end; node.increment(error)) { const boost::filesystem::path& path = node->path(); // ... } In other words, I suspect that we need to check that node.increment(error) in the for loop did not give an error before checking the condition "node != end", or else we may enter the loop in case of error and then it may access node->path() with an invalid node iterator. I could not find in the doc at ... https://www.boost.org/doc/libs/1_75_0/libs/filesystem/doc/reference.html ... what exactly happens when node.increment(error) gives an error. Perhaps the doc deserves clarification or an example illustrating how to reliably iterate over files without using exceptions would be welcome. Thanks Dominique

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Serialization and static Libraries
by Wolfgang Meyerle 20 Jan '21

20 Jan '21

Hi, probably has been asked already thousand of times but I'm stuck currently with some code: Assuming I have the following files (The Base class Action is serialized in the same way): File: Ping.h #include"Action.h" classPing:publicAction{ public: voidoperator()(); Ping(); Ping*clone()const; ~Ping(); template<typenameArchive> voidserialize(Archive&ar,constunsignedint); }; BOOST_CLASS_EXPORT_KEY2(Ping,"Ping"); File: Ping.cpp #include"Ping.h" #include<iostream> #include<boost/serialization/base_object.hpp> #include<boost/serialization/export.hpp> #include<boost/serialization/tracking.hpp> #include"Action.h" #include"system.h" #include"pong.h" #include"serializerdeserializer.h" #include"system.h" #include"connection.h" #include"communication.h" voidPing::operator()(){ } Ping::Ping() { } Ping*Ping::clone()const{ Ping*ping=newPing(*this); returnping; } template<typenameArchive> voidPing::serialize(Archive&ar,constunsignedint){ ar&BOOST_SERIALIZATION_BASE_OBJECT_NVP(Action); } Ping::~Ping(){} BOOST_CLASS_EXPORT_IMPLEMENT(Ping); BOOST_CLASS_TRACKING(Ping,boost::serialization::track_never); If I now compile the project into a library. And link this library to a different project. If I try to serialize the class now it doesn't work. I get the following error: unregistered class - derived class not registered or exported According to the boost documentation I need to use BOOST_CLASS_EXPORT_KEY in the header file and BOOST_CLASS_EXPORT_IMPLEMENT in the corresponding cpp file. What did I miss? Regards, Wolfgang

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[Boost-MPI][Boost-ODEINT] Running odeint within MPI-context without using mpi_state
by Roland Richter 19 Jan '21

19 Jan '21

Hei, I am currently using the odeint-solver for calculating the right hand side of a non-linear equation. For speeding up the calculation of the right hand side, I decided to test the MPI-implementation. Now, after I would prefer to keep the code backwards compatible, I did not want to replace state_type with mpi_state, and instead split up the initial vector by hand before calling odeint without telling odeint that I am operating within an MPI context. I take care of all communications which involve the vectors, and therefore I assumed that this approach should work (especially after it worked correctly in small test programs). Nevertheless, I encountered the issue that after a certain amount of steps the step size between the different threads starts to differ by a small amount, even though I am in the same iteration. As example: step number rank step size n 1 0.00025 n 0 0.00025 //Ok n + 1 1 0.00051152 n + 1 0 0.000511523 //Not ok I checked my program with valgrind for possible memory leaks/corruption which could overwrite something, but nothing relevant came up. The problem is repeatable. Therefore, is the general idea correct at all, or am I doing something wrong here by neglecting a possible communication between the different threads within odeint? Thanks! Regards, Roland

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Conversion numeric::array in numpy::ndarray
by philippe DALET 17 Jan '21

17 Jan '21

Hello, It's my first mail on this maillist. I started to upgrade a package for python 3.7, 3.8, 3.9 (linux and windows): vpython-wx. One file gives me some problems num_util.hpp My context: ubuntu 20.04: boost 1.71 python3.7 windows 10: boost 1.75 python3.7, 3.8, 3.9 I want to create a double_array class: Original version --------------------- namespace cvisual { namespace python { using boost::python::numeric::array; class double_array : public array { public: explicit double_array( const boost::python::handle<>& h ) : array(h) {} }; array makeNum(npy_intp n, NPY_TYPES t =NPY_DOUBLE); New version ----------------- namespace cvisual { namespace python { using boost::python::numpy::ndarray; class double_array : public ndarray { public: explicit double_array( const boost::python::handle<>& h ) : ndarray(h) {} }; ndarray makeNum(npy_intp n, NPY_TYPES t =NPY_DOUBLE); error message with VC2019 community error conversion 'const boost::python::handle<PyObject>' in 'boost::python::detail::borrowed_reference' error message with gcc 9.3 no matching function for call to ‘boost::python::numpy::ndarray::ndarray(const boost::python::handle<>&)’ Thanks a lot for your help. Philippe DALET Laboratoire de Physique Lyp Champollion, Figeac FRANCE

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Re: [Boost-users] boost::regex: regex meta data or AST for regex?
by Frank Bergemann 16 Jan '21

16 Jan '21

On 16.12.20 18:05, Frank Bergemann via Boost-users wrote: > in concrete: > Is it possible to not only get the #no of groups (sub-expressions) via > basic_regex::mark_count(), but also their position (begin() / end() > iterators) in the given regex string (c'tor argument)? > > more general: > Can an AST be created for a the given regex string (c'tor argument)? > E.g with boost::spirit? I am busy with #2 parsers: 1) RegexParser: Intended to be a full regular expression parser https://github.com/F-Bergemann/RegexParser 2) RegexSplitter: to just break up regular expression into substrings for top level regex-group & non-regex-group substrings: https://github.com/F-Bergemann/RegexSplitter It's just a start and so much wrong within, i know. But i have one concrete question for the RegexSplitter: How can i avoid in RegexSplitter.cpp to use #157 ( tok_element >> *tok_element ) [ qi::_val = phx::new_<ASTNode> (qi::_1, qi::_2, ASTNode::COLLECTION_c) ]; I want to pass a SINGLE std::vector<ATSNode *> only to the receiving #51 // COLLECTION_c #52 ASTNode::ASTNode( #53 ASTNode const * first, #54 std::vector<ASTNode *> & others, #55 Type const type) without the SEPARATE parameter 'first'. I.e. i need to "merge" qi::_1 and qi::_2.

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Re: [Boost-users] boost ptr_map memory access violation
by roland kapl 08 Jan '21

08 Jan '21

Dear All! After finding some inspiration on https://stackoverflow.com/questions/4088387/how-to-store-pointers-in-map , I've succeeded storing the property tree pointers in a std::map... std::string TreeizeRelD::writeTree(const std::vector<std::vector<std::string>> &control, const std::vector<std::vector<std::vector<std::string>>> &data, pt::ptree & ptTree) { // now the map is local... typedef std::map<std::string, pt::ptree*> treeMap; std::map<std::string, treeMap> parentTableTrees; .... std::string subRootNode = parentNode + (subnodeOfParent != "" ? "." + subnodeOfParent : ""); std::string tableLookup = subRootNode + "." + rootElemRec; // simply add records if no foreign key name exists (usually the top (root) table) if (foreignKeyName == "") { for (std::pair<std::string, pt::ptree> && keyPair : tables[tableLookup]) { parentTableTrees[subRootNode].insert(std::make_pair(keyPair.first, &ptTree.add_child(subRootNode, keyPair.second))); ... // iterate through all parent key record collections referred to by subtables parentNode (rootnode + optional subnode) for (std::pair<std::string, pt::ptree*> && parentKeysPair : parentTableTrees.find(lookupNode)->second) { // iterate through all records (ptrees) in key collection for (pt::ptree::iterator parentRecPair = parentKeysPair.second->begin(); parentRecPair != parentKeysPair.second->end(); ++parentRecPair) { // important here: assign a reference to parentRecPtree (pointer!), otherwise a copy is created! pt::ptree &parentRecPtree = parentRecPair->second; ... parentTableTrees[subRootNode].insert(std::make_pair(rowsFK, &parentRecPair->second.get_child(subnodeFRec))); ... parentTableTrees[subRootNode].insert(std::make_pair(rowsFK, &parentRecPtree.put_child(subnodeOfParent, foreignRecordset))); The complete source of this: https://github.com/rkapl123/OreControl/blob/master/OreMgr/TreeizeRelD/treei… -regards, Roland ---------------------------------------------------------------------- Message: 1 Date: Wed, 6 Jan 2021 11:49:07 +0000 From: roland kapl <roland.kapl(a)hotmail.com<mailto:roland.kapl@hotmail.com>> To: "boost-users(a)lists.boost.org<mailto:boost-users@lists.boost.org>" <boost-users(a)lists.boost.org<mailto:boost-users@lists.boost.org>> Subject: [Boost-users] boost ptr_map memory access violation (stack/heap problem) Message-ID: <AM0PR03MB424285F7832EDC3C73C96860EDD00(a)AM0PR03MB4242.eurprd03.prod.outlook.com<mailto:AM0PR03MB424285F7832EDC3C73C96860EDD00@AM0PR03MB4242.eurprd03.prod.outlook.com>> Content-Type: text/plain; charset="us-ascii" Dear Boost-Experts! I'm trying to use a ptr_map along with boost property trees. I need to store pointers to specific parts of a built up property tree to access these parts later on for easy insertion there. However, when the ptr_map is cleared/destroyed, I get memory access violations/stack overflow messages for my test cases. The ptr_map (typedef treeMap) is globally defined within a std::map to a ptr_map to property trees as follows (I know this isn't good practice, but passing it as a reference didn't make a difference, so I left it that way): namespace pt = boost::property_tree; typedef boost::ptr_map<std::string, pt::ptree> treeMap; std::map<std::string, treeMap> parentTableTrees; The property tree is defined as follows in this function (this builds a property tree from tabular data in the passed table variable "data" using definitions form table variable "control"): std::string TreeizeRelD::writeTreeAndCreateXML(const std::vector<std::vector<std::string>>& control, const std::vector<std::vector<std::vector<std::string>>>& data, int *result) { std::string resultString; pt::ptree &propTree = pt::ptree(); std::string returnStr = TreeizeRelD::writeTree(control, data, propTree); *result = 0; if (returnStr != "") { *result = 1; return returnStr; } returnStr = TreeizeRelD::createXML(propTree, resultString); if (returnStr != "") { *result = 1; return returnStr; } // here the memory access violation occurs: parentTableTrees.clear(); return resultString; } In function writeTree the propTree (being passed by ref as ptTree) is populated in following three lines: std::string TreeizeRelD::writeTree(const std::vector<std::vector<std::string>> &control, const std::vector<std::vector<std::vector<std::string>>> &data, pt::ptree & ptTree) ... // FIRST LINE parentTableTrees[subRootNode].insert(keyPair.first, &ptTree.add_child(subRootNode, keyPair.second)); ... // iterate through all parent key record collections referred to by subtables parentNode (rootnode + optional subnode) for (treeMap::value_type && parentKeysPair : parentTableTrees.find(lookupNode)->second) { // iterate through all records (ptrees) in key collection for (pt::ptree::iterator parentRecPair = parentKeysPair.second->begin(); parentRecPair != parentKeysPair.second->end(); ++parentRecPair) { pt::ptree &parentRecPtree = parentRecPair->second; ... // SECOND LINE // parentRecPair is an iterator variable from the ptr_map: parentTableTrees[subRootNode].insert(rowsFK, &parentRecPair->second.get_child(subnodeFRec)); ... // THIRD LINE // parentRecPtree is the referenced property tree itself: parentTableTrees[subRootNode].insert(rowsFK, &parentRecPtree.put_child(subnodeOfParent, foreignRecordset)); I already have the suspicion that the memory access violation comes from ptr_map taking ownership of the pointers (references) passed to it in the above three lines and that these are all created on the stack and not the heap, where ptr_map expects them to be. When the ptr_map is finally destroyed, it tries to access memory, that's impossible to access... But I didn't manage to successfully create heap objects that also do NOT copy the property tree objects, which is important as I only need references to the property trees. Any help is appreciated. -regards, Roland

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boost ptr_map memory access violation (stack/heap problem)
by roland kapl 06 Jan '21

06 Jan '21

Dear Boost-Experts! I'm trying to use a ptr_map along with boost property trees. I need to store pointers to specific parts of a built up property tree to access these parts later on for easy insertion there. However, when the ptr_map is cleared/destroyed, I get memory access violations/stack overflow messages for my test cases. The ptr_map (typedef treeMap) is globally defined within a std::map to a ptr_map to property trees as follows (I know this isn't good practice, but passing it as a reference didn't make a difference, so I left it that way): namespace pt = boost::property_tree; typedef boost::ptr_map<std::string, pt::ptree> treeMap; std::map<std::string, treeMap> parentTableTrees; The property tree is defined as follows in this function (this builds a property tree from tabular data in the passed table variable "data" using definitions form table variable "control"): std::string TreeizeRelD::writeTreeAndCreateXML(const std::vector<std::vector<std::string>>& control, const std::vector<std::vector<std::vector<std::string>>>& data, int *result) { std::string resultString; pt::ptree &propTree = pt::ptree(); std::string returnStr = TreeizeRelD::writeTree(control, data, propTree); *result = 0; if (returnStr != "") { *result = 1; return returnStr; } returnStr = TreeizeRelD::createXML(propTree, resultString); if (returnStr != "") { *result = 1; return returnStr; } // here the memory access violation occurs: parentTableTrees.clear(); return resultString; } In function writeTree the propTree (being passed by ref as ptTree) is populated in following three lines: std::string TreeizeRelD::writeTree(const std::vector<std::vector<std::string>> &control, const std::vector<std::vector<std::vector<std::string>>> &data, pt::ptree & ptTree) ... // FIRST LINE parentTableTrees[subRootNode].insert(keyPair.first, &ptTree.add_child(subRootNode, keyPair.second)); ... // iterate through all parent key record collections referred to by subtables parentNode (rootnode + optional subnode) for (treeMap::value_type && parentKeysPair : parentTableTrees.find(lookupNode)->second) { // iterate through all records (ptrees) in key collection for (pt::ptree::iterator parentRecPair = parentKeysPair.second->begin(); parentRecPair != parentKeysPair.second->end(); ++parentRecPair) { pt::ptree &parentRecPtree = parentRecPair->second; ... // SECOND LINE // parentRecPair is an iterator variable from the ptr_map: parentTableTrees[subRootNode].insert(rowsFK, &parentRecPair->second.get_child(subnodeFRec)); ... // THIRD LINE // parentRecPtree is the referenced property tree itself: parentTableTrees[subRootNode].insert(rowsFK, &parentRecPtree.put_child(subnodeOfParent, foreignRecordset)); I already have the suspicion that the memory access violation comes from ptr_map taking ownership of the pointers (references) passed to it in the above three lines and that these are all created on the stack and not the heap, where ptr_map expects them to be. When the ptr_map is finally destroyed, it tries to access memory, that's impossible to access... But I didn't manage to successfully create heap objects that also do NOT copy the property tree objects, which is important as I only need references to the property trees. Any help is appreciated. -regards, Roland

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[statechart] Event dispatching for orthogonal states
by B A 03 Jan '21

03 Jan '21

Hello, I have following code : ///////////////////////////////////////////// #include <iostream> #include <boost/mpl/list.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/event.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> namespace sc = boost::statechart; struct Event1 : sc::event<Event1> {}; struct Event11 : sc::event<Event11> {}; struct Meta; struct Machine : sc::state_machine<Machine, Meta> {}; struct Meta2 : sc::simple_state<Meta2, Machine> { Meta2() { std::cout << "Meta2\n"; } }; struct Inner1; struct Inner2; struct Meta : sc::simple_state<Meta, Machine, boost::mpl::list<Inner1, Inner2>> { Meta() { std::cout << "Meta\n"; } typedef sc::transition<Event1, Meta2> reactions; }; struct Inner11 : sc::simple_state<Inner11, Meta::orthogonal<0>> { Inner11() { std::cout << "Inner11\n"; } typedef sc::custom_reaction<Event1> reactions; sc::result react(const Event1& ev) { std::cout << "Inner1 reaction\n"; return forward_event(); } }; struct Inner1 : sc::simple_state<Inner1, Meta::orthogonal<0>> { Inner1() { std::cout << "Inner1\n"; } typedef sc::transition<Event11, Inner11> reactions; }; struct Inner2 : sc::simple_state<Inner2, Meta::orthogonal<1>> { Inner2() { std::cout << "Inner2\n"; } }; int main() { Machine m; m.initiate(); m.process_event(Event11()); m.process_event(Event1()); return 0; } //////////////////// That gives me output: Meta Inner1 Inner2 Inner11 Meta2 The goal was to get Event1 processed first in Inner11 state and then forward it to outer state Meta for further processing but looks like event dispatching does not work as expected. I can make it work in that way only if I put Event1 handling into Inner1 state. I'm aware of limitation (https://www.boost.org/doc/libs/1_61_0/libs/statechart/doc/rationale.html#Li… #Event dispatch to orthogonal regions) but as far I understand that considers that case when both Inner1 and Inner11 have same event processing, please correct me if I'm wrong. Is current dispatching work correctly for my code? Regards, Andrew

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BOOST_DLL_ALIAS - non Latin AliasName
by Nicholas Yue 02 Jan '21

02 Jan '21

Hi, The examples I have seen so far appears to use ASCII name for AliasName I am considering providing AliasName in languages like Chinese, Korean, Japanese, Thai, Tamil, does Boost DLL allow for wstring/UNICODE as AliasName ? Cheers -- Nicholas Yue Graphics - Arnold, Alembic, RenderMan, OpenGL, HDF5 Custom Dev - C++ porting, OSX, Linux, Windows http://au.linkedin.com/in/nicholasyue https://vimeo.com/channels/naiadtools

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shutdown( ) blocks forever
by Fariya F 30 Dec '20

30 Dec '20

I have a server that accepts ssl connections on port 443. I am using the boost libraries for the server implementation. Below is the code snippet: ssl_socket socket_; { // Open the acceptor with the option to reuse the address (i.e. SO_REUSEADDR). boost::asio::ip::tcp::resolver resolver(io_service_); boost::asio::ip::tcp::resolver::query query(address, port); boost::asio::ip::tcp::endpoint endpoint = *resolver.resolve(query); acceptor_.open(endpoint.protocol()); acceptor_.set_option(boost::asio::ip::tcp::acceptor::reuse_address(true)); acceptor_.bind(endpoint); acceptor_.listen(1000); start_accept(); } void server::start_accept() { new_connection_.reset( new connection(io_service_, connection_manager_, request_handler_, context_)); acceptor_.async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } void server::handle_accept(const boost::system::error_code& e) { // Check whether the server was stopped by a signal before this completion // handler had a chance to run. if (!acceptor_.is_open()) { return; } else { start(); } start_accept(); } void server::start() { socket_.async_handshake(boost::asio::ssl::stream_base::server, boost::bind(&connection::handle_handshake, this, boost::asio::placeholders::error)); if (boost::asio::placeholders::error) { // printf("Error is there. Check it\n"); } } void connection::handle_handshake(const boost::system::error_code& error) { if (!error) { DEBUG("async read some"); socket_.async_read_some(boost::asio::buffer(buffer_), boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } else { std::cout << "Error number: " << error.value(); std::cout << " Error message: " << error.message(); std::cout << " Error category: " << error.category().name() << std::endl; delete this; } } When I initiate multiple clients to connect to the server, most of the time the connection succeeds i.e TCP handshake followed by SSL handshake succeeds and I am able to do data transfer. However, there are times when the TCP handshake succeeds (as seen by wireshark) but the SSL request isn't responded to by my server. I am able to see the SSL handshake request coming from the client onto my server, but the server doesn't respond, neither is my handle_accept() function gets called. When I check the output of netstat, I see a lot of data pending in the Recv-Q. Below is the output of netstat -atn command on the server during one such scenario: Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 15 0 0.0.0.0:443 0.0.0.0:* LISTEN tcp 0 213 10.110.112.1:443 10.110.112.2:52363 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52624 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52581 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52646 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52749 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52824 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52805 ESTABLISHED tcp 180 0 10.110.112.1:443 10.110.112.2:52645 ESTABLISHED tcp 0 471 10.110.112.1:443 10.110.112.2:52362 ESTABLISHED tcp 1 0 10.110.112.1:443 10.110.112.3:39129 CLOSE_WAIT tcp 183 0 10.110.112.1:443 10.110.112.3:39130 CLOSE_WAIT tcp 180 0 10.110.112.1:443 10.110.112.2:52595 ESTABLISHED tcp 183 0 10.110.112.1:443 10.110.112.3:39131 CLOSE_WAIT Upon further debugging, I see that the call to ssl socket member function shutdown() blocks sometimes forever and sometimes for at least 5 - 10 minutes due to which no further data is taken in and the recv-q indicates pending bytes. This is how my write handler is. Any help on where I am going wrong would be greatly appreciated: void connection::handle_write(const boost::system::error_code& e) { if (!e) { boost::system::error_code ec; socket_.shutdown(ec); //Code blocks here indefinitely } } Any reasons why the socket_.shutdown( ) blocks. How could I specify a timeout such that the shutdown( ) returns back after some time? Any other way of handling this? ( I know there is async_shutdown( ) but I prefer using shutdown( ) blocking handler) Any help would be greatly appreciated. Regards, Fariya

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