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• Linking errors when building against Boost Unit Test Framework

  - by Rafid

  I am trying to use Boost Unit Test Framework by building a stand alone library as detailed here: http://www.boost.org/doc/libs/1_35_0/libs/test/doc/components/utf/compilation.html So I created a VC library project containing the mentioned files and build it and it was successful. Then I created a test project and referenced the library project I just created, but when I tried to build it, I got the following linking errors: 1>Type.obj : error LNK2019: unresolved external symbol "bool __cdecl boost::test_tools::tt_detail::check_impl(class boost::test_tools::predicate_result const &,class boost::unit_test::lazy_ostream const &,class boost::unit_test::basic_cstring<char const >,unsigned __int64,enum boost::test_tools::tt_detail::tool_level,enum boost::test_tools::tt_detail::check_type,unsigned __int64,...)" (?check_impl@tt_detail@test_tools@boost@@YA_NAEBVpredicate_result@23@AEBVlazy_ostream@unit_test@3@V?$basic_cstring@$$CBD@63@_KW4tool_level@123@W4check_type@123@3ZZ) referenced in function "public: void __cdecl test1::test_method(void)" (?test_method@test1@@QEAAXXZ) 1>BoostUnitTestFramework.lib(framework.obj) : error LNK2019: unresolved external symbol "void __cdecl boost::debug::break_memory_alloc(long)" (?break_memory_alloc@debug@boost@@YAXJ@Z) referenced in function "void __cdecl boost::unit_test::framework::init(class boost::unit_test::test_suite * (__cdecl*)(int,char * * const),int,char * * const)" (?init@framework@unit_test@boost@@YAXP6APEAVtest_suite@23@HQEAPEAD@ZH0@Z) 1>BoostUnitTestFramework.lib(framework.obj) : error LNK2019: unresolved external symbol "void __cdecl boost::debug::detect_memory_leaks(bool)" (?detect_memory_leaks@debug@boost@@YAX_N@Z) referenced in function "void __cdecl boost::unit_test::framework::init(class boost::unit_test::test_suite * (__cdecl*)(int,char * * const),int,char * * const)" (?init@framework@unit_test@boost@@YAXP6APEAVtest_suite@23@HQEAPEAD@ZH0@Z) 1>BoostUnitTestFramework.lib(execution_monitor.obj) : error LNK2019: unresolved external symbol "bool __cdecl boost::debug::attach_debugger(bool)" (?attach_debugger@debug@boost@@YA_N_N@Z) referenced in function "public: int __cdecl boost::detail::system_signal_exception::operator()(unsigned int,struct _EXCEPTION_POINTERS *)" (??Rsystem_signal_exception@detail@boost@@QEAAHIPEAU_EXCEPTION_POINTERS@@@Z) 1>BoostUnitTestFramework.lib(execution_monitor.obj) : error LNK2019: unresolved external symbol "bool __cdecl boost::debug::under_debugger(void)" (?under_debugger@debug@boost@@YA_NXZ) referenced in function "public: int __cdecl boost::execution_monitor::execute(class boost::unit_test::callback0<int> const &)" (?execute@execution_monitor@boost@@QEAAHAEBV?$callback0@H@unit_test@2@@Z) 1>BoostUnitTestFramework.lib(unit_test_main.obj) : error LNK2019: unresolved external symbol "class boost::unit_test::test_suite * __cdecl init_unit_test_suite(int,char * * const)" (?init_unit_test_suite@@YAPEAVtest_suite@unit_test@boost@@HQEAPEAD@Z) referenced in function main 1>C:\Users\Rafid\Workspace\MyPhysics\Builds\VC10\Tests\Debug\Tests.exe : fatal error LNK1120: 6 unresolved externals They seem to be mainly caused by Boost debug library, but I can't see a reason why I should get linking errors putting in mind that Boost debug library only need to be included as header files, rather than linking against as a library! Any ideas?!

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• css positioning

  - by bsreekanth

  Hello, I have uploaded a part of my screen below (link: http://yfrog.com/0d30127380p) It is part of a forum, so there are elements above and below it. The "Response Req.. Date" has a label, a date picker, and two drop down select control for time. I tried setting the width of the datepicker element, and a right margin so that the time selectors would position next to it. But it always sit below it. I'm not good in css positioning, so any suggestion would be highly appreciated. <div class="wrapper "> <label for="responseRequiredDate"> Response Required Date <span class="indicator">*</span> </label> <input type="hidden" name="responseRequiredDate" value="struct" /><div class="datetimepicker"> <div class="datePicker"> </div> <script> ...</script> <div class="timepicker"><select .... </div> </div> the date picker insert a script tag, would that cause a problem. probably not.

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• Help with Boost Spirit ASTs

  - by Decmac04

  I am writing a small tool for analyzing simple B Machine substitutions as part of a college research work. The code successfully parse test inputs of the form mySubst := var1 + var2. However, I get a pop-up error message saying "This application has requested the Runtime to terminate it in an unusual way. " In the command prompt window, I get an "Assertion failed message". The main program is given below: // BMachineTree.cpp : Defines the entry point for the console application. // /*============================================================================= Copyright (c) 2010 Temitope Onunkun =============================================================================*/ /////////////////////////////////////////////////////////////////////////////// // // UUsing Boost Spririt Trees (AST) to parse B Machine Substitutions. // /////////////////////////////////////////////////////////////////////////////// #define BOOST_SPIRIT_DUMP_PARSETREE_AS_XML #include <boost/spirit/core.hpp> #include <boost/spirit/tree/ast.hpp> #include <boost/spirit/tree/tree_to_xml.hpp> #include "BMachineTreeGrammar.hpp" #include <iostream> #include <stack> #include <functional> #include <string> #include <cassert> #include <vector> #if defined(BOOST_SPIRIT_DUMP_PARSETREE_AS_XML) #include <map> #endif // Using AST to parse B Machine substitutions //////////////////////////////////////////////////////////////////////////// using namespace std; using namespace boost::spirit; typedef char const* iterator_t; typedef tree_match<iterator_t> parse_tree_match_t; typedef parse_tree_match_t::tree_iterator iter_t; //////////////////////////////////////////////////////////////////////////// string evaluate(parse_tree_match_t hit); string eval_machine(iter_t const& i); vector<string> dx; string evaluate(tree_parse_info<> info) { return eval_machine(info.trees.begin()); } string eval_machine(iter_t const& i) { cout << "In eval_machine. i->value = " << string(i->value.begin(), i->value.end()) << " i->children.size() = " << i->children.size() << endl; if (i->value.id() == substitution::leafValueID) { assert(i->children.size() == 0); // extract string tokens string leafValue(i->value.begin(), i->value.end()); dx.push_back(leafValue.c_str()); return leafValue.c_str(); } // else if (i->value.id() == substitution::termID) { if ( (*i->value.begin() == '*') || (*i->value.begin() == '/') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + " " + eval_machine(i->children.begin()+1); } // else assert(0); } else if (i->value.id() == substitution::expressionID) { if ( (*i->value.begin() == '+') || (*i->value.begin() == '-') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + " " + eval_machine(i->children.begin()+1); } else assert(0); } // else if (i->value.id() == substitution::simple_substID) { if (*i->value.begin() == (':' >> '=') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + "|->" + eval_machine(i->children.begin()+1); } else assert(0); } else { assert(0); // error } return 0; } //////////////////////////////////////////////////////////////////////////// int main() { // look in BMachineTreeGrammar for the definition of BMachine substitution BMach_subst; cout << "/////////////////////////////////////////////////////////\n\n"; cout << "\t\tB Machine Substitution...\n\n"; cout << "/////////////////////////////////////////////////////////\n\n"; cout << "Type an expression...or [q or Q] to quit\n\n"; string str; while (getline(cin, str)) { if (str.empty() || str[0] == 'q' || str[0] == 'Q') break; tree_parse_info<> info = ast_parse(str.c_str(), BMach_subst, space_p); if (info.full) { #if defined(BOOST_SPIRIT_DUMP_PARSETREE_AS_XML) // dump parse tree as XML std::map<parser_id, std::string> rule_names; rule_names[substitution::identifierID] = "identifier"; rule_names[substitution::leafValueID] = "leafValue"; rule_names[substitution::factorID] = "factor"; rule_names[substitution::termID] = "term"; rule_names[substitution::expressionID] = "expression"; rule_names[substitution::simple_substID] = "simple_subst"; tree_to_xml(cout, info.trees, str.c_str(), rule_names); #endif // print the result cout << "Variables in Vector dx: " << endl; for(vector<string>::iterator idx = dx.begin(); idx < dx.end(); ++idx) cout << *idx << endl; cout << "parsing succeeded\n"; cout << "result = " << evaluate(info) << "\n\n"; } else { cout << "parsing failed\n"; } } cout << "Bye... :-) \n\n"; return 0; } The grammar, defined in BMachineTreeGrammar.hpp file is given below: /*============================================================================= Copyright (c) 2010 Temitope Onunkun http://www.dcs.kcl.ac.uk/pg/onun Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) =============================================================================*/ #ifndef BOOST_SPIRIT_BMachineTreeGrammar_HPP_ #define BOOST_SPIRIT_BMachineTreeGrammar_HPP_ using namespace boost::spirit; /////////////////////////////////////////////////////////////////////////////// // // Using Boost Spririt Trees (AST) to parse B Machine Substitutions. // /////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////// // // B Machine Grammar // //////////////////////////////////////////////////////////////////////////// struct substitution : public grammar<substitution> { static const int identifierID = 1; static const int leafValueID = 2; static const int factorID = 3; static const int termID = 4; static const int expressionID = 5; static const int simple_substID = 6; template <typename ScannerT> struct definition { definition(substitution const& ) { // Start grammar definition identifier = alpha_p >> (+alnum_p | ch_p('_') ) ; leafValue = leaf_node_d[ lexeme_d[ identifier | +digit_p ] ] ; factor = leafValue | inner_node_d[ ch_p( '(' ) >> expression >> ch_p(')' ) ] ; term = factor >> *( (root_node_d[ch_p('*') ] >> factor ) | (root_node_d[ch_p('/') ] >> factor ) ); expression = term >> *( (root_node_d[ch_p('+') ] >> term ) | (root_node_d[ch_p('-') ] >> term ) ); simple_subst= leaf_node_d[ lexeme_d[ identifier ] ] >> root_node_d[str_p(":=")] >> expression ; // End grammar definition // turn on the debugging info. BOOST_SPIRIT_DEBUG_RULE(identifier); BOOST_SPIRIT_DEBUG_RULE(leafValue); BOOST_SPIRIT_DEBUG_RULE(factor); BOOST_SPIRIT_DEBUG_RULE(term); BOOST_SPIRIT_DEBUG_RULE(expression); BOOST_SPIRIT_DEBUG_RULE(simple_subst); } rule<ScannerT, parser_context<>, parser_tag<simple_substID> > simple_subst; rule<ScannerT, parser_context<>, parser_tag<expressionID> > expression; rule<ScannerT, parser_context<>, parser_tag<termID> > term; rule<ScannerT, parser_context<>, parser_tag<factorID> > factor; rule<ScannerT, parser_context<>, parser_tag<leafValueID> > leafValue; rule<ScannerT, parser_context<>, parser_tag<identifierID> > identifier; rule<ScannerT, parser_context<>, parser_tag<simple_substID> > const& start() const { return simple_subst; } }; }; #endif The output I get on running the program is: ///////////////////////////////////////////////////////// B Machine Substitution... ///////////////////////////////////////////////////////// Type an expression...or [q or Q] to quit mySubst := var1 - var2 parsing succeeded In eval_machine. i->value = := i->children.size() = 2 Assertion failed: 0, file c:\redmound\bmachinetree\bmachinetree\bmachinetree.cpp , line 114 I will appreciate any help in resolving this problem.

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• Reinterpret a CGImageRef using PyObjC in Python

  - by Michael Rondinelli

  Hi, I'm doing something that's a little complicated to sum up in the title, so please bear with me. I'm writing a Python module that provides an interface to my C++ library, which provides some specialized image manipulation functionality. It would be most convenient to be able to access image buffers as CGImageRefs from Python, so they could be manipulated further using Quartz (using PyObjC, which works well). So I have a C++ function that provides a CGImageRef representation from my own image buffers, like this: CGImageRef CreateCGImageRefForImageBuffer(shared_ptr<ImageBuffer> buffer); I'm using Boost::Python to create my Python bridge. What is the easiest way for me to export this function so that I can use the CGImageRef from Python? Problems: The CGImageRef type can't be exported directly because it is a pointer to an undefined struct. So I could make a wrapper function that wraps it in a PyCObject or something to get it to send the pointer to Python. But then how do I "cast" this object to a CGImageRef from Python? Is there a better way to go about this?

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• What is the best way to send structs containing enum values via sockets in C.

  - by Axel

  I've lots of different structs containing enum members that I have to transmit via TCP/IP. While the communication endpoints are on different operating systems (Windows XP and Linux) meaning different compilers (gcc 4.x.x and MSVC 2008) both program parts share the same header files with type declarations. For performance reasons, the structures should be transmitted directly (see code sample below) without expensively serializing or streaming the members inside. So the question is how to ensure that both compilers use the same internal memory representation for the enumeration members (i.e. both use 32-bit unsigned integers). Or if there is a better way to solve this problem... //type and enum declaration typedef enum { A = 1, B = 2, C = 3 } eParameter; typedef enum { READY = 400, RUNNING = 401, BLOCKED = 402 FINISHED = 403 } eState; #pragma pack(push,1) typedef struct { eParameter mParameter; eState mState; int32_t miSomeValue; uint8_t miAnotherValue; ... } tStateMessage; #pragma pack(pop) //... send via socket tStateMessage msg; send(iSocketFD,(void*)(&msg),sizeof(tStateMessage)); //... receive message on the other side tStateMessage msg_received; recv(iSocketFD,(void*)(&msg_received),sizeof(tStateMessage)); Additionally... Since both endpoints are little endian maschines, endianess is not a problem here. And the pack #pragma solves alignment issues satisfactorily. Thx for your answers, Axel

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• AVL tree in C language

  - by I_S_W

  Hey all; i am currently doing a project that requires the use of AVL trees , the insert function i wrote for the avl does not seem to be working , it works for 3 or 4 nodes at maximum ; i would really appreciate your help The attempt is below enter code here Tree insert(Tree t,char name[80],int num) { if(t==NULL) { t=(Tree)malloc(sizeof(struct node)); if(t!=NULL) { strcpy(t->name,name); t->num=num; t->left=NULL; t->right=NULL; t->height=0; } } else if(strcmp(name,t->name)<0) { t->left=insert(t->left,name,num); if((height(t->left)-height(t->right))==2) if(strcmp(name,t->left->name)<0) { t=s_rotate_left(t);} else{ t=d_rotate_left(t);} } else if(strcmp(name,t-name)0) { t-right=insert(t-right,name,num); if((height(t-right)-height(t-left))==2) if(strcmp(name,t-right-name)0){ t=s_rotate_right(t); } else{ t=d_rotate_right(t);} } t-height=max(height(t-left),height(t-right))+1; return t; }

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• C++ design question on traversing binary trees

  - by user231536

  I have a binary tree T which I would like to copy to another tree. Suppose I have a visit method that gets evaluated at every node: struct visit { virtual void operator() (node* n)=0; }; and I have a visitor algorithm void visitor(node* t, visit& v) { //do a preorder traversal using stack or recursion if (!t) return; v(t); visitor(t->left, v); visitor(t->right, v); } I have 2 questions: I settled on using the functor based approach because I see that boost graph does this (vertex visitors). Also I tend to repeat the same code to traverse the tree and do different things at each node. Is this a good design to get rid of duplicated code? What other alternative designs are there? How do I use this to create a new binary tree from an existing one? I can keep a stack on the visit functor if I want, but it gets tied to the algorithm in visitor. How would I incorporate postorder traversals here ? Another functor class?

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• XML Serialize and Deserialize Problem XML Structure

  - by Ph.E

  Camarades, I'm having the following problem. Caught a list Struct, Serialize (Valid W3C) and send to a WebService. In the WebService I receive, transform to a string, valid by the W3C and then Deserializer, but when I try to run it, always occurs error, saying that some objects were not closed. Any help? Sent Code: #region ListToXML private XmlDocument ListToXMLDocument(object __Lista) { XmlDocument _ListToXMLDocument = new XmlDocument(); try { XmlDocument _XMLDoc = new XmlDocument(); MemoryStream _StreamMem = new MemoryStream(); XmlSerializer _XMLSerial = new XmlSerializer(__Lista.GetType()); StreamWriter _StreamWriter = new StreamWriter(_StreamMem, Encoding.UTF8); _XMLSerial.Serialize(_StreamWriter, __Lista); _StreamMem.Position = 0; _XMLDoc.Load(_StreamMem); if (_XMLDoc.ChildNodes.Count > 0) _ListToXMLDocument = _XMLDoc; } catch (Exception __Excp) { new uException(__Excp).GerarLogErro(CtNomeBiblioteca); } return _ListToXMLDocument; } #endregion Receive Code: #region XMLDocumentToTypedList private List<T> XMLDocumentToTypedList<T>(string __XMLDocument) { List<T> _XMLDocumentToTypedList = new List<T>(); try { XmlSerializer _XMLSerial = new XmlSerializer(typeof(List<T>)); MemoryStream _MemStream = new MemoryStream(); StreamWriter _StreamWriter = new StreamWriter(_MemStream, Encoding.UTF8); _StreamWriter.Write(__XMLDocument); _MemStream.Position = 0; _XMLDocumentToTypedList = (List<T>)_XMLSerial.Deserialize(_MemStream); return _XMLDocumentToTypedList; } catch (Exception _Ex) { new uException(_Ex).GerarLogErro(CtNomeBiblioteca); throw _Ex; } } #endregion

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• OpenNETCF.Stopwatch -> only ticks changing, not Elapsed

  - by pithyless

  I've been trying to track down a bug I thought was thread-related, but I think instead there is an issue with the way I am using OpenNETCF's Stopwatch. I am using OpenNETCF.IoC in my application, but for the sake of simplicity I moved the following code directly into a view: public partial class WorkoutView : SmartPart { ... private Stopwatch stopwatch; public WorkoutView() { ... stopwatch = new Stopwatch(); stopwatch.Reset(); stopwatch.Start(); WorkoutDisplayTimer = new Timer(); WorkoutDisplayTimer.Interval = 500; WorkoutDisplayTimer.Tick += new EventHandler(WorkoutDisplayTimer_Tick); WorkoutDisplayTimer.Enabled = true; } void WorkoutDisplayTimer_Tick(object sender, EventArgs e) { ... stopwatch.Stop(); lbl.Text = stopwatch.ElapsedTicks.ToString() + "NOT WORKING: " + stopwatch.Elapsed.ToString(); stopwatch.Start(); } ... } Long story short, looking at stopwatch in the debugger, the only values that ever get updated are ElapsedTicks, mElapsed, mStartPerfCount. Everything else is always zero. Is this expected behavior? Do I need to call an additional method to have the stopwatch calculate the Elapsed struct? (Note: stopwatch.ElapsedMilliseconds is also zero)

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• What sorting algorithm is this?

  - by Mike

  Hi, I have a sorting algorithm as follows. My question is, which sorting algorithm is this? I thought it was bubble sort, but it does not do multiple runs. Any idea? Thanks! //sorting in descending order struct node { int value; node* NEXT; } //Assume HEAD pointer denotes the first element in the //linked list // only change the values…don’t have to change the //pointers Sort( Node *Head) { node* first,second,temp; first= Head; while(first!=null) { second=first->NEXT; while(second!=null) { if(first->value < second->value) { temp = new node(); temp->value=first->value; first->value=second->value; second->value=temp->value; delete temp; } second=second->NEXT; } first=first->NEXT; } }

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• Call dll - pcshll32.dll using delphi

  - by Davis

  Hi, I need to call hllapi function of pcshll32.dll using delphi. It's works with personal communications of ibm. How can i change the code bellow to delphi ? Thanks !!! The EHLLAPI entry point (hllapi) is always called with the following four parameters: EHLLAPI Function Number (input) Data Buffer (input/output) Buffer Length (input/output) Presentation Space Position (input); Return Code (output) The prototype for IBM Standard EHLLAPI is: [long hllapi (LPWORD, LPSTR, LPWORD, LPWORD); The prototype for IBM Enhanced EHLLAPI is: [long hllapi (LPINT, LPSTR, LPINT, LPINT); Each parameter is passed by reference not by value. Thus each parameter to the function call must be a pointer to the value, not the value itself. For example, the following is a correct example of calling the EHLLAPI Query Session Status function: #include "hapi_c.h" struct HLDQuerySessionStatus QueryData; int Func, Len, Rc; long Rc; memset(QueryData, 0, sizeof(QueryData)); // Init buffer QueryData.qsst_shortname = ©A©; // Session to query Func = HA_QUERY_SESSION_STATUS; // Function number Len = sizeof(QueryData); // Len of buffer Rc = 0; // Unused on input hllapi(&Func, (char *)&QueryData, &Len, &Rc); // Call EHLLAPI if (Rc != 0) { // Check return code // ...Error handling } All the parameters in the hllapi call are pointers and the return code of the EHLLAPI function is returned in the value of the 4th parameter, not as the value of the function.

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• Execution time in nano seconds and related issues

  - by anup

  Hi All, I am using the following code to compute execution time in milli-secs. struct timespec tp; if (clock_gettime (CLOCK_REALTIME, &tp) == 0) return ((tp.tv_sec * 1000000000) + tp.tv_nsec); else return ; Can you please tell me whether this is correct? Let's name this function comptime_nano(). Now, I write the following code in main() to check execution times of following operations. unsigned long int a, b, s1, s3; a = (unsigned long int)(1) << 63; b = (unsigned long int)(1) << 63; btime = comptime_nano(); s1 = b >> 30; atime = comptime_nano(); printf ("Time =%ld for %lu\n", (atime - btime), s1); btime = comptime_nano(); s3 = a >> 1; atime = comptime_nano(); printf ("Time =%ld for %lu\n", (atime - btime), s3); To my surprise, the first operation takes about roughly 4 times more time than the second. Again, if I change the relative ordering of these operations, the respective timings change drastically. Please comment...

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• Python: combining making two scripts into one

  - by Alex

  I have two separately made python scripts one that makes a sine wave sound based off time, and another that produces a sine wave graph that is based off the same time factors. I need help combining them into one running file. Here's the first: from struct import pack from math import sin, pi import time def au_file(name, freq, freq1, dur, vol): fout = open(name, 'wb') # header needs size, encoding=2, sampling_rate=8000, channel=1 fout.write('.snd' + pack('>5L', 24, 8*dur, 2, 8000, 1)) factor = 2 * pi * freq/8000 factor1 = 2 * pi * freq1/8000 # write data for seg in range(8 * dur): # sine wave calculations sin_seg = sin(seg * factor) + sin(seg * factor1) fout.write(pack('b', vol * 64 * sin_seg)) fout.close() t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis * 100 tim = float(ti) tim = tim * 100 if __name__ == '__main__': au_file(name='timeSound.au', freq=tim, freq1=tis, dur=1000, vol=1.0) import os os.startfile('timeSound.au') and the second is this: from Tkinter import * import math import time t = time.strftime("%S", time.localtime()) ti = time.strftime("%M", time.localtime()) tis = float(t) tis = tis / 100 tim = float(ti) tim = tim / 100 root = Tk() root.title("This very moment") width = 400 height = 300 center = height//2 x_increment = 1 # width stretch x_factor1 = tis x_factor2 = tim # height stretch y_amplitude = 50 c = Canvas(width=width, height=height, bg='black') c.pack() str1 = "sin(x)=white" c.create_text(10, 20, anchor=SW, text=str1) center_line = c.create_line(0, center, width, center, fill='red') # create the coordinate list for the sin() curve, have to be integers xy1 = [] xy2 = [] for x in range(400): # x coordinates xy1.append(x * x_increment) xy2.append(x * x_increment) # y coordinates xy1.append(int(math.sin(x * x_factor1) * y_amplitude) + center) xy2.append(int(math.sin(x * x_factor2) * y_amplitude) + center) sinS_line = c.create_line(xy1, fill='white') sinM_line = c.create_line(xy2, fill='yellow') root.mainloop()

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• Removing padding from structure in kernel module

  - by dexkid

  I am compiling a kernel module, containing a structure of size 34, using the standard command. make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules The sizeof(some_structure) is coming as 36 instead of 34 i.e. the compiler is padding the structure. How do I remove this padding? Running make V=1 shows the gcc compiler options passed as make -I../inc -C /lib/modules/2.6.29.4-167.fc11.i686.PAE/build M=/home/vishal/20100426_eth_vishal/organised_eth/src modules make[1]: Entering directory `/usr/src/kernels/2.6.29.4-167.fc11.i686.PAE' test -e include/linux/autoconf.h -a -e include/config/auto.conf || ( \ echo; \ echo " ERROR: Kernel configuration is invalid."; \ echo " include/linux/autoconf.h or include/config/auto.conf are missing."; \ echo " Run 'make oldconfig && make prepare' on kernel src to fix it."; \ echo; \ /bin/false) mkdir -p /home/vishal/20100426_eth_vishal/organised_eth/src/.tmp_versions ; rm -f /home/vishal/20100426_eth_vishal/organised_eth/src/.tmp_versions/* make -f scripts/Makefile.build obj=/home/vishal/20100426_eth_vishal/organised_eth/src gcc -Wp,-MD,/home/vishal/20100426_eth_vishal/organised_eth/src/.eth_main.o.d -nostdinc -isystem /usr/lib/gcc/i586-redhat-linux/4.4.0/include -Iinclude -I/usr/src/kernels/2.6.29.4-167.fc11.i686.PAE/arch/x86/include -include include/linux/autoconf.h -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Os -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=generic -Wa,-mtune=generic32 -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Iarch/x86/include/asm/mach-generic -Iarch/x86/include/asm/mach-default -Wframe-larger-than=1024 -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -pg -Wdeclaration-after-statement -Wno-pointer-sign -fwrapv -fno-dwarf2-cfi-asm -DTX_DESCRIPTOR_IN_SYSTEM_MEMORY -DRX_DESCRIPTOR_IN_SYSTEM_MEMORY -DTX_BUFFER_IN_SYSTEM_MEMORY -DRX_BUFFER_IN_SYSTEM_MEMORY -DALTERNATE_DESCRIPTORS -DEXT_8_BYTE_DESCRIPTOR -O0 -Wall -DT_ETH_1588_051 -DALTERNATE_DESCRIPTORS -DEXT_8_BYTE_DESCRIPTOR -DNETHERNET_INTERRUPTS -DETH_IEEE1588_TESTS -DSNAPTYPSEL_TMSTRENA_TEVENTENA_TESTS -DT_ETH_1588_140_147 -DLOW_DEBUG_PRINTS -DMEDIUM_DEBUG_PRINTS -DHIGH_DEBUG_PRINTS -DMODULE -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(eth_main)" -D"KBUILD_MODNAME=KBUILD_STR(conxt_eth)" -c -o /home/vishal/20100426_eth_vishal/organised_eth/src/eth_main.o /home/vishal/20100426_eth_vishal/organised_eth/src/eth_main.c

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• Multiplication algorithm for abritrary precision (bignum) integers.

  - by nn

  Hi, I'm writing a small bignum library for a homework project. I am to implement Karatsuba multiplication, but before that I would like to write a naive multiplication routine. I'm following a guide written by Paul Zimmerman titled "Modern Computer Arithmetic" which is freely available online. On page 4, there is a description of an algorithm titled BasecaseMultiply which performs gradeschool multiplication. I understand step 2, 3, where B^j is a digit shift of 1, j times. But I don't understand step 1 and 3, where we have A*b_j. How is this multiplication meant to be carried out if the bignum multiplication hasn't been defined yet? Would the operation "*" in this algorithm just be the repeated addition method? Here is the parts I have written thus far. I have unit tested them so they appear to be correct for the most part: The structure I use for my bignum is as follows: #define BIGNUM_DIGITS 2048 typedef uint32_t u_hw; // halfword typedef uint64_t u_w; // word typedef struct { unsigned int sign; // 0 or 1 unsigned int n_digits; u_hw digits[BIGNUM_DIGITS]; } bn; Currently available routines: bn *bn_add(bn *a, bn *b); // returns a+b as a newly allocated bn void bn_lshift(bn *b, int d); // shifts d digits to the left, retains sign int bn_cmp(bn *a, bn *b); // returns 1 if a>b, 0 if a=b, -1 if a<b

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• Variant datatype library for C

  - by Joey Adams

  Is there a decent open-source C library for storing and manipulating dynamically-typed variables (a.k.a. variants)? I'm primarily interested in atomic values (int8, int16, int32, uint, strings, blobs, etc.), while JSON-style arrays and objects as well as custom objects would also be nice. A major case where such a library would be useful is in working with SQL databases. The most obvious feature of such a library would be a single type for all supported values, e.g.: struct Variant { enum Type type; union { int8_t int8_; int16_t int16_; // ... }; }; Other features might include converting Variant objects to/from C structures (using a binding table), converting values to/from strings, and integration with an existing database library such as SQLite. Note: I do not believe this is question is a duplicate of http://stackoverflow.com/questions/649649/any-library-for-generic-datatypes-in-c , which refers to "queues, trees, maps, lists". What I'm talking about focuses more on making working with SQL databases roughly as smooth as working with them in interpreted languages.

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• Query on simple C++ threadpool implementation

  - by ticketman

  Stackoverflow has been a tremendous help to me and I'd to give something back to the community. I have been implementing a simple threadpool using the tinythread C++ portable thread library, using what I have learnt from Stackoverflow. I am new to thread programming, so not that comfortable with mutexes, etc. I have a question best asked after presenting the code (which runs quite well under Linux): // ThreadPool.h class ThreadPool { public: ThreadPool(); ~ThreadPool(); // Creates a pool of threads and gets them ready to be used void CreateThreads(int numOfThreads); // Assigns a job to a thread in the pool, but doesn't start the job // Each SubmitJob call will use up one thread of the pool. // This operation can only be undone by calling StartJobs and // then waiting for the jobs to complete. On completion, // new jobs may be submitted. void SubmitJob( void (*workFunc)(void *), void *workData ); // Begins execution of all the jobs in the pool. void StartJobs(); // Waits until all jobs have completed. // The wait will block the caller. // On completion, new jobs may be submitted. void WaitForJobsToComplete(); private: enum typeOfWorkEnum { e_work, e_quit }; class ThreadData { public: bool ready; // thread has been created and is ready for work bool haveWorkToDo; typeOfWorkEnum typeOfWork; // Pointer to the work function each thread has to call. void (*workFunc)(void *); // Pointer to work data void *workData; ThreadData() : ready(false), haveWorkToDo(false) { }; }; struct ThreadArgStruct { ThreadPool *threadPoolInstance; int threadId; }; // Data for each thread ThreadData *m_ThreadData; ThreadPool(ThreadPool const&); // copy ctor hidden ThreadPool& operator=(ThreadPool const&); // assign op. hidden // Static function that provides the function pointer that a thread can call // By including the ThreadPool instance in the void * parameter, // we can use it to access other data and methods in the ThreadPool instance. static void ThreadFuncWrapper(void *arg) { ThreadArgStruct *threadArg = static_cast<ThreadArgStruct *>(arg); threadArg->threadPoolInstance->ThreadFunc(threadArg->threadId); } // The function each thread calls void ThreadFunc( int threadId ); // Called by the thread pool destructor void DestroyThreadPool(); // Total number of threads available // (fixed on creation of thread pool) int m_numOfThreads; int m_NumOfThreadsDoingWork; int m_NumOfThreadsGivenJobs; // List of threads std::vector<tthread::thread *> m_ThreadList; // Condition variable to signal each thread has been created and executing tthread::mutex m_ThreadReady_mutex; tthread::condition_variable m_ThreadReady_condvar; // Condition variable to signal each thread to start work tthread::mutex m_WorkToDo_mutex; tthread::condition_variable m_WorkToDo_condvar; // Condition variable to signal the main thread that // all threads in the pool have completed their work tthread::mutex m_WorkCompleted_mutex; tthread::condition_variable m_WorkCompleted_condvar; }; cpp file: // // ThreadPool.cpp // #include "ThreadPool.h" // This is the thread function for each thread. // All threads remain in this function until // they are asked to quit, which only happens // when terminating the thread pool. void ThreadPool::ThreadFunc( int threadId ) { ThreadData *myThreadData = &m_ThreadData[threadId]; std::cout << "Hello world: Thread " << threadId << std::endl; // Signal that this thread is ready m_ThreadReady_mutex.lock(); myThreadData->ready = true; m_ThreadReady_condvar.notify_one(); // notify the main thread m_ThreadReady_mutex.unlock(); while(true) { //tthread::lock_guard<tthread::mutex> guard(m); m_WorkToDo_mutex.lock(); while(!myThreadData->haveWorkToDo) // check for work to do m_WorkToDo_condvar.wait(m_WorkToDo_mutex); // if no work, wait here myThreadData->haveWorkToDo = false; // need to do this before unlocking the mutex m_WorkToDo_mutex.unlock(); // Do the work switch(myThreadData->typeOfWork) { case e_work: std::cout << "Thread " << threadId << ": Woken with work to do\n"; // Do work myThreadData->workFunc(myThreadData->workData); std::cout << "#Thread " << threadId << ": Work is completed\n"; break; case e_quit: std::cout << "Thread " << threadId << ": Asked to quit\n"; return; // ends the thread } // Now to signal the main thread that my work is completed m_WorkCompleted_mutex.lock(); m_NumOfThreadsDoingWork--; // Unsure if this 'if' would make the program more efficient // if(NumOfThreadsDoingWork == 0) m_WorkCompleted_condvar.notify_one(); // notify the main thread m_WorkCompleted_mutex.unlock(); } } ThreadPool::ThreadPool() { m_numOfThreads = 0; m_NumOfThreadsDoingWork = 0; m_NumOfThreadsGivenJobs = 0; } ThreadPool::~ThreadPool() { if(m_numOfThreads) { DestroyThreadPool(); delete [] m_ThreadData; } } void ThreadPool::CreateThreads(int numOfThreads) { // Check a thread pool has already been created if(m_numOfThreads > 0) return; m_NumOfThreadsGivenJobs = 0; m_NumOfThreadsDoingWork = 0; m_numOfThreads = numOfThreads; m_ThreadData = new ThreadData[m_numOfThreads]; ThreadArgStruct threadArg; for(int i=0; i<m_numOfThreads; ++i) { threadArg.threadId = i; threadArg.threadPoolInstance = this; // Creates the thread and save in a list so we can destroy it later m_ThreadList.push_back( new tthread::thread( ThreadFuncWrapper, (void *)&threadArg ) ); // It takes a little time for a thread to get established. // Best wait until it gets established before creating the next thread. m_ThreadReady_mutex.lock(); while(!m_ThreadData[i].ready) // Check if thread is ready m_ThreadReady_condvar.wait(m_ThreadReady_mutex); // If not, wait here m_ThreadReady_mutex.unlock(); } } // Adds a job to the batch, but doesn't start the job void ThreadPool::SubmitJob(void (*workFunc)(void *), void *workData) { // Check that the thread pool has been created if(!m_numOfThreads) return; if(m_NumOfThreadsGivenJobs >= m_numOfThreads) return; m_ThreadData[m_NumOfThreadsGivenJobs].workFunc = workFunc; m_ThreadData[m_NumOfThreadsGivenJobs].workData = workData; std::cout << "Submitted job " << m_NumOfThreadsGivenJobs << std::endl; m_NumOfThreadsGivenJobs++; } void ThreadPool::StartJobs() { // Check that the thread pool has been created // and some jobs have been assigned if(!m_numOfThreads || !m_NumOfThreadsGivenJobs) return; // Set 'haveworkToDo' flag for all threads m_WorkToDo_mutex.lock(); for(int i=0; i<m_NumOfThreadsGivenJobs; ++i) m_ThreadData[i].haveWorkToDo = true; m_NumOfThreadsDoingWork = m_NumOfThreadsGivenJobs; // Reset this counter so we can resubmit jobs later m_NumOfThreadsGivenJobs = 0; // Notify all threads they have work to do m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); } void ThreadPool::WaitForJobsToComplete() { // Check that a thread pool has been created if(!m_numOfThreads) return; m_WorkCompleted_mutex.lock(); while(m_NumOfThreadsDoingWork > 0) // Check if all threads have completed their work m_WorkCompleted_condvar.wait(m_WorkCompleted_mutex); // If not, wait here m_WorkCompleted_mutex.unlock(); } void ThreadPool::DestroyThreadPool() { std::cout << "Ask threads to quit\n"; m_WorkToDo_mutex.lock(); for(int i=0; i<m_numOfThreads; ++i) { m_ThreadData[i].haveWorkToDo = true; m_ThreadData[i].typeOfWork = e_quit; } m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); // As each thread terminates, catch them here for(int i=0; i<m_numOfThreads; ++i) { tthread::thread *t = m_ThreadList[i]; // Wait for thread to complete t->join(); } m_numOfThreads = 0; } Example of usage: (this calculates pi-squared/6) struct CalculationDataStruct { int inputVal; double outputVal; }; void LongCalculation( void *theSums ) { CalculationDataStruct *sums = (CalculationDataStruct *)theSums; int terms = sums->inputVal; double sum; for(int i=1; i<terms; i++) sum += 1.0/( double(i)*double(i) ); sums->outputVal = sum; } int main(int argc, char** argv) { int numThreads = 10; // Create pool ThreadPool threadPool; threadPool.CreateThreads(numThreads); // Create thread workspace CalculationDataStruct sums[numThreads]; // Set up jobs for(int i=0; i<numThreads; i++) { sums[i].inputVal = 3000*(i+1); threadPool.SubmitJob(LongCalculation, &sums[i]); } // Run the jobs threadPool.StartJobs(); threadPool.WaitForJobsToComplete(); // Print results for(int i=0; i<numThreads; i++) std::cout << "Sum of " << sums[i].inputVal << " terms is " << sums[i].outputVal << std::endl; return 0; } Question: In the ThreadPool::ThreadFunc method, would better performance be obtained if the following if statement if(NumOfThreadsDoingWork == 0) was included? Also, I'd be grateful of criticisms and ways to improve the code. At the same time, I hope the code is of use to others.

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• Why am I getting 'Heap Corruption'?

  - by fneep

  Please don't crucify me for this one. I decided it might be good to use a char* because the string I intended to build was of a known size. I am also aware that if timeinfo-tm_hour returns something other than 2 digits, things are going to go badly wrong. That said, when this function returns VIsual Studio goes ape at me about HEAP CORRUPTION. What's going wrong? (Also, should I just use a stringbuilder?) void cLogger::_writelogmessage(std::string Message) { time_t rawtime; struct tm* timeinfo = 0; time(&rawtime); timeinfo = localtime(&rawtime); char* MessageBuffer = new char[Message.length()+11]; char* msgptr = MessageBuffer; _itoa(timeinfo->tm_hour, msgptr, 10); msgptr+=2; strcpy(msgptr, "::"); msgptr+=2; _itoa(timeinfo->tm_min, msgptr, 10); msgptr+=2; strcpy(msgptr, "::"); msgptr+=2; _itoa(timeinfo->tm_sec, msgptr, 10); msgptr+=2; strcpy(msgptr, " "); msgptr+=1; strcpy(msgptr, Message.c_str()); _file << MessageBuffer; delete[] MessageBuffer; }

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• Two classes and inline functions

  - by klew

  I have two classes and both of them uses some of the other class, on example: // class1.h class Class1; #include "class2.h" class Class1 { public: static Class2 *C2; ... }; // class2.h class Class2; #include "class1.h" class Class2 { public: static Class1 *C1; ... }; And when I define it like in example above, it works (I also have some #ifndef to avoid infinite header recurency). But I also want to add some inline functions to my classes. And I read here that I should put definition of inline function in header file, because it won't work if I'll put them in cpp file and want to call them from other cpp file (when I do it I get undefined reference during linking). But the problem here is with something like this: // class1.h ... inline void Class1::Foo() { C2->Bar(); } I get error: invalid use of incomplete type ‘struct Class2’. So how can I do it?

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• is delete p where p is a pointer to array a memory leak ?

  - by Eli

  following a discussion in a software meeting I setup to find out if deleting an dynamically allocated primitive array with plain delete will cause a memory leak. I have written this tiny program and compiled with visual studio 2008 running on windows XP: #include "stdafx.h" #include "Windows.h" const unsigned long BLOCK_SIZE = 1024*100000; int _tmain() { for (unsigned int i =0; i < 1024*1000; i++) { int* p = new int[1024*100000]; for (int j =0;j<BLOCK_SIZE;j++) p[j]= j % 2; Sleep(1000); delete p; } } I than monitored the memory consumption of my application using task manager, surprisingly the memory was allocated and freed correctly, allocated memory did not steadily increase as was expected I've modified my test program to allocate a non primitive type array : #include "stdafx.h" #include "Windows.h" struct aStruct { aStruct() : i(1), j(0) {} int i; char j; } NonePrimitive; const unsigned long BLOCK_SIZE = 1024*100000; int _tmain() { for (unsigned int i =0; i < 1024*100000; i++) { aStruct* p = new aStruct[1024*100000]; Sleep(1000); delete p; } } after running for for 10 minutes there was no meaningful increase in memory I compiled the project with warning level 4 and got no warnings. is it possible that the visual studio run time keep track of the allocated objects types so there is no different between delete and delete[] in that environment ?

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• cURL requests changed

  - by Andriy Mytroshyn

  I've start work with cURL library, before work i compile library. i Send request and have some problem. Code in c++ that i used for work with cURL: CURL *curl=NULL; CURLcode res; struct curl_slist *headers=NULL; // init to NULL is important curl_slist_append(headers, "POST /oauth/authorize HTTP/1.1"); curl_slist_append(headers, "Host: sp-money.yandex.ru"); curl_slist_append(headers, "Content-Type: application/x-www-form-urlencoded"); curl_slist_append(headers, "charset: UTF-8"); curl_slist_append(headers, "Content-Length: 12345"); curl = curl_easy_init(); if(!curl) return 0; curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers); curl_easy_setopt(curl, CURLOPT_URL, "sp-money.yandex.ru"); curl_easy_setopt(curl, CURLOPT_PROXY, "127.0.0.1:8888"); if( curl_easy_perform(curl)!=CURLE_OK) return 1; I've used proxy, fiddler2, for check what data sent to server. When i check sent data i get result: POST HTTP://sp-money.yandex.ru/ HTTP/1.1 Host: sp-money.yandex.ru Accept: */* Connection: Keep-Alive Content-Length: 151 Content-Type: application/x-www-form-urlencoded also i check this data using Wiresharck, result the same. Do you know why in first line cURL wrote: POST HTTP://sp-money.yandex.ru/ HTTP/1.1 I send POST /oauth/authorize HTTP/1.1 I've used VS 2010 for work, and also i don't used framework

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• GCC emits extra code for boost::shared_ptr dereference

  - by Checkers

  I have the following code: #include <boost/shared_ptr.hpp> struct Foo { int a; }; static int A; void func_shared(const boost::shared_ptr<Foo> &foo) { A = foo->a; } void func_raw(Foo * const foo) { A = foo->a; } I thought the compiler would create identical code, but for shared_ptr version an extra seemingly redundant instruction is emitted. Disassembly of section .text: 00000000 <func_raw(Foo*)>: 0: 55 push ebp 1: 89 e5 mov ebp,esp 3: 8b 45 08 mov eax,DWORD PTR [ebp+8] 6: 5d pop ebp 7: 8b 00 mov eax,DWORD PTR [eax] 9: a3 00 00 00 00 mov ds:0x0,eax e: c3 ret f: 90 nop 00000010 <func_shared(boost::shared_ptr<Foo> const&)>: 10: 55 push ebp 11: 89 e5 mov ebp,esp 13: 8b 45 08 mov eax,DWORD PTR [ebp+8] 16: 5d pop ebp 17: 8b 00 mov eax,DWORD PTR [eax] 19: 8b 00 mov eax,DWORD PTR [eax] 1b: a3 00 00 00 00 mov ds:0x0,eax 20: c3 ret I'm just curious, is this necessary, or it is just an optimizer's shortcoming? Compiling with g++ 4.1.2, -O3 -NDEBUG.

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• ubuntu: sem_timedwait not waking (C)

  - by gillez

  I have 3 processes which need to be synchronized. Process one does something then wakes process two and sleeps, which does something then wakes process three and sleeps, which does something and wakes process one and sleeps. The whole loop is timed to run around 25hz (caused by an external sync into process one before it triggers process two in my "real" application). I use sem_post to trigger (wake) each process, and sem_timedwait() to wait for the trigger. This all works successfully for several hours. However at some random time (usually after somewhere between two and four hours), one of the processes starts timing out in sem_timedwait(), even though I am sure the semaphore is being triggered with sem_post(). To prove this I even use sem_getvalue() immediately after the timeout, and the value is 1, so the timedwait should have been triggered. Please see following code: #include <stdio.h> #include <time.h> #include <string.h> #include <errno.h> #include <semaphore.h> sem_t trigger_sem1, trigger_sem2, trigger_sem3; // The main thread process. Called three times with a different num arg - 1, 2 or 3. void *thread(void *arg) { int num = (int) arg; sem_t *wait, *trigger; int val, retval; struct timespec ts; struct timeval tv; switch (num) { case 1: wait = &trigger_sem1; trigger = &trigger_sem2; break; case 2: wait = &trigger_sem2; trigger = &trigger_sem3; break; case 3: wait = &trigger_sem3; trigger = &trigger_sem1; break; } while (1) { // The first thread delays by 40ms to time the whole loop. // This is an external sync in the real app. if (num == 1) usleep(40000); // print sem value before we wait. If this is 1, sem_timedwait() will // return immediately, otherwise it will block until sem_post() is called on this sem. sem_getvalue(wait, &val); printf("sem%d wait sync sem%d. val before %d\n", num, num, val); // get current time and add half a second for timeout. gettimeofday(&tv, NULL); ts.tv_sec = tv.tv_sec; ts.tv_nsec = (tv.tv_usec + 500000); // add half a second if (ts.tv_nsec > 1000000) { ts.tv_sec++; ts.tv_nsec -= 1000000; } ts.tv_nsec *= 1000; /* convert to nanosecs */ retval = sem_timedwait(wait, &ts); if (retval == -1) { // timed out. Print value of sem now. This should be 0, otherwise sem_timedwait // would have woken before timeout (unless the sem_post happened between the // timeout and this call to sem_getvalue). sem_getvalue(wait, &val); printf("!!!!!! sem%d sem_timedwait failed: %s, val now %d\n", num, strerror(errno), val); } else printf("sem%d wakeup.\n", num); // get value of semaphore to trigger. If it's 1, don't post as it has already been // triggered and sem_timedwait on this sem *should* not block. sem_getvalue(trigger, &val); if (val <= 0) { printf("sem%d send sync sem%d. val before %d\n", num, (num == 3 ? 1 : num+1), val); sem_post(trigger); } else printf("!! sem%d not sending sync, val %d\n", num, val); } } int main(int argc, char *argv[]) { pthread_t t1, t2, t3; // create semaphores. val of sem1 is 1 to trigger straight away and start the whole ball rolling. if (sem_init(&trigger_sem1, 0, 1) == -1) perror("Error creating trigger_listman semaphore"); if (sem_init(&trigger_sem2, 0, 0) == -1) perror("Error creating trigger_comms semaphore"); if (sem_init(&trigger_sem3, 0, 0) == -1) perror("Error creating trigger_vws semaphore"); pthread_create(&t1, NULL, thread, (void *) 1); pthread_create(&t2, NULL, thread, (void *) 2); pthread_create(&t3, NULL, thread, (void *) 3); pthread_join(t1, NULL); pthread_join(t2, NULL); pthread_join(t3, NULL); } The following output is printed when the program is running correctly (at the start and for a random but long time after). The value of sem1 is always 1 before thread1 waits as it sleeps for 40ms, by which time sem3 has triggered it, so it wakes straight away. The other two threads wait until the semaphore is received from the previous thread. [...] sem1 wait sync sem1. val before 1 sem1 wakeup. sem1 send sync sem2. val before 0 sem2 wakeup. sem2 send sync sem3. val before 0 sem2 wait sync sem2. val before 0 sem3 wakeup. sem3 send sync sem1. val before 0 sem3 wait sync sem3. val before 0 sem1 wait sync sem1. val before 1 sem1 wakeup. sem1 send sync sem2. val before 0 [...] However, after a few hours, one of the threads begins to timeout. I can see from the output that the semaphore is being triggered, and when I print the value after the timeout is is 1. So sem_timedwait should have woken up well before the timeout. I would never expect the value of the semaphore to be 1 after the timeout, save for the very rare occasion (almost certainly never but it's possible) when the trigger happens after the timeout but before I call sem_getvalue. Also, once it begins to fail, every sem_timedwait() on that semaphore also fails in the same way. See the following output, which I've line-numbered: 01 sem3 wait sync sem3. val before 0 02 sem1 wakeup. 03 sem1 send sync sem2. val before 0 04 sem2 wakeup. 05 sem2 send sync sem3. val before 0 06 sem2 wait sync sem2. val before 0 07 sem1 wait sync sem1. val before 0 08 !!!!!! sem3 sem_timedwait failed: Connection timed out, val now 1 09 sem3 send sync sem1. val before 0 10 sem3 wait sync sem3. val before 1 11 sem3 wakeup. 12 !! sem3 not sending sync, val 1 13 sem3 wait sync sem3. val before 0 14 sem1 wakeup. [...] On line 1, thread 3 (which I have confusingly called sem1 in the printf) waits for sem3 to be triggered. On line 5, sem2 calls sem_post for sem3. However, line 8 shows sem3 timing out, but the value of the semaphore is 1. thread3 then triggers sem1 and waits again (10). However, because the value is already 1, it wakes straight away. It doesn't send sem1 again as this has all happened before control is given to thread1, however it then waits again (val is now 0) and sem1 wakes up. This now repeats for ever, sem3 always timing out and showing that the value is 1. So, my question is why does sem3 timeout, even though the semaphore has been triggered and the value is clearly 1? I would never expect to see line 08 in the output. If it times out (because, say thread 2 has crashed or is taking too long), the value should be 0. And why does it work fine for 3 or 4 hours first before getting into this state? This is using Ubuntu 9.4 with kernel 2.6.28. The same procedure has been working properly on Redhat and Fedora. But I'm now trying to port to ubuntu! Thanks for any advice, Giles

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• valgrind complains doing a very simple strtok in c

  - by monkeyking

  Hi I'm trying to tokenize a string by loading an entire file into a char[] using fread. For some strange reason it is not always working, and valgrind complains in this very small sample program. Given an input like test.txt first second And the following program #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/stat.h> //returns the filesize in bytes size_t fsize(const char* fname){ struct stat st ; stat(fname,&st); return st.st_size; } int main(int argc, char *argv[]){ FILE *fp = NULL; if(NULL==(fp=fopen(argv[1],"r"))){ fprintf(stderr,"\t-> Error reading file:%s\n",argv[1]); return 0; } char buffer[fsize(argv[1])]; fread(buffer,sizeof(char),fsize(argv[1]),fp); char *str = strtok(buffer," \t\n"); while(NULL!=str){ fprintf(stderr,"token is:%s with strlen:%lu\n",str,strlen(str)); str = strtok(NULL," \t\n"); } return 0; } compiling like gcc test.c -std=c99 -ggdb running like ./a.out test.txt thanks

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• boost lambda::bind return type selection

  - by psaghelyi

  I would like to call a member through lambda::bind. Unfortunately I have got to members with the same name but different return type. Is there a way to help the lambda::bind to deduce the right return type for a member function call? #include <vector> #include <iostream> #include <algorithm> #include <boost/bind.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> using namespace std; using namespace boost; struct A { A (const string & name) : m_name(name) {} string & name () { return m_name; } const string & name () const { return m_name; } string m_name; }; vector<A> av; int main () { av.push_back (A ("some name")); // compiles fine find_if(av.begin(), av.end(), bind<const string &>(&A::name, _1) == "some name"); // error: call of overloaded 'bind(<unresolved overloaded function type>, const boost::lambda::lambda_functor<boost::lambda::placeholder<1> >&)' is ambiguous find_if(av.begin(), av.end(), lambda::bind(&A::name, lambda::_1) == "some name"); return 0; }

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