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  • C++ MySQL++ Delete query statement brain killer question

    - by shauny
    Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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  • C++/msvc6 application crashes due to heap corruption, any hints?

    - by David Alfonso
    Hello all, let me say first that I'm writing this question after months of trying to find out the root of a crash happening in our application. I'll try to detail as much as possible what I've already found out about it. About the application It runs on Windows XP Professional SP2. It's built with Microsoft Visual C++ 6.0 with Service Pack 6. It's MFC based. It uses several external dlls (e.g. Xerces, ZLib or ACE). It has high performance requirements. It does a lot of network and hard disk I/O, but it's also cpu intensive. It has an exception handling mechanism which generates a minidump when an unhandled exception occurs. Facts about the crash It only happens on multiprocessor/multicore machines and under heavy loads of work. It happens at random (neither we nor our client have found a pattern yet). We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines) It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols) ChildEBP RetAddr Args to Child WARNING: Stack unwind information not available. Following frames may be wrong. 030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9 030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0]) 030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo]) 030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96 030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo]) 030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0]) 030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b 030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo]) 7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo]) 7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff 7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be *** WARNING: Unable to verify checksum for xerces-c_2_7.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll - 7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff 7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7 7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be 7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090 7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list. What I have tried so far Reviewing all the code related to the point where the crash ends happening. Trying to enable pageheap on our testing lab though nothing useful has been found by now. We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump: ntdll.dll!_RtlpCoalesceFreeBlocks@16() + 0x124e bytes ntdll.dll!_RtlFreeHeap@12() + 0x91f bytes msvcrt.dll!_free() + 0xc3 bytes MyApplication.exe!006a4fda() [Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe] MyApplication.exe!0069f305() ntdll.dll!_NtFreeVirtualMemory@16() + 0xc bytes ntdll.dll!_RtlpSecMemFreeVirtualMemory@16() + 0x1b bytes ntdll.dll!_ZwWaitForSingleObject@12() + 0xc bytes ntdll.dll!_RtlpFreeToHeapLookaside@8() + 0x26 bytes ntdll.dll!_RtlFreeHeap@12() + 0x114 bytes msvcrt.dll!_free() + 0xc3 bytes c5ffffff() Possible solutions (that I'm aware of) which cannot be applied "Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment. "Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily. I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer! Thank you in advance for your time and advice.

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  • Constructor ambiguous quesiton

    - by Crystal
    I'm trying to create a simple date class, but I get an error on my main file that says, "call of overloaded Date() is ambiguous." I'm not sure why since I thought as long as I had different parameters for my constructor, I was ok. Here is my code: header file: #ifndef DATE_H #define DATE_H using std::string; class Date { public: static const int monthsPerYear = 12; // num of months in a yr Date(int = 1, int = 1, int = 1900); // default constructor Date(); // uses system time to create object void print() const; // print date in month/day/year format ~Date(); // provided to confirm destruction order string getMonth(int month) const; // gets month in text format private: int month; // 1 - 12 int day; // 1 - 31 int year; // any year int checkDay(int) const; }; #endif .cpp file #include <iostream> #include <iomanip> #include <string> #include <ctime> #include "Date.h" using namespace std; Date::Date() { time_t seconds = time(NULL); struct tm* t = localtime(&seconds); month = t->tm_mon; day = t->tm_mday; year = t->tm_year; } Date::Date(int mn, int dy, int yr) { if (mn > 0 && mn <= monthsPerYear) month = mn; else { month = 1; // invalid month set to 1 cout << "Invalid month (" << mn << ") set to 1.\n"; } year = yr; // could validate yr day = checkDay(dy); // validate the day // output Date object to show when its constructor is called cout << "Date object constructor for date "; print(); cout << endl; } void Date::print() const { string str; cout << month << '/' << day << '/' << year << '\n'; // new code for HW2 cout << setfill('0') << setw(3) << day; // prints in ddd cout << " " << year << '\n'; // yyyy format str = getMonth(month); // prints in month (full word), day, year cout << str << " " << day << ", " << year << '\n'; } and my main.cpp #include <iostream> #include "Date.h" using std::cout; int main() { Date date1(4, 30, 1980); date1.print(); cout << '\n'; Date date2; date2.print(); }

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  • Filling in gaps for outlines

    - by user146780
    I'm using an algorithm to generate quads. These become outlines. The algorithm is: void OGLENGINEFUNCTIONS::GenerateLinePoly(const std::vector<std::vector<GLdouble>> &input, std::vector<GLfloat> &output, int width) { output.clear(); if(input.size() < 2) { return; } int temp; float dirlen; float perplen; POINTFLOAT start; POINTFLOAT end; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; POINTFLOAT p0, p1, p2, p3; for(unsigned int i = 0; i < input.size() - 1; ++i) { start.x = static_cast<float>(input[i][0]); start.y = static_cast<float>(input[i][1]); end.x = static_cast<float>(input[i + 1][0]); end.y = static_cast<float>(input[i + 1][1]); dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = static_cast<float>(dir.x * 1.0 / dirlen); ndir.y = static_cast<float>(dir.y * 1.0 / dirlen); perp.x = dir.y; perp.y = -dir.x; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = static_cast<float>(perp.x * 1.0 / perplen); nperp.y = static_cast<float>(perp.y * 1.0 / perplen); perpoffset.x = static_cast<float>(nperp.x * width * 0.5); perpoffset.y = static_cast<float>(nperp.y * width * 0.5); diroffset.x = static_cast<float>(ndir.x * 0 * 0.5); diroffset.y = static_cast<float>(ndir.y * 0 * 0.5); // p0 = start + perpoffset - diroffset //p1 = start - perpoffset - diroffset //p2 = end + perpoffset + diroffset // p3 = end - perpoffset + diroffset p0.x = start.x + perpoffset.x - diroffset.x; p0.y = start.y + perpoffset.y - diroffset.y; p1.x = start.x - perpoffset.x - diroffset.x; p1.y = start.y - perpoffset.y - diroffset.y; p2.x = end.x + perpoffset.x + diroffset.x; p2.y = end.y + perpoffset.y + diroffset.y; p3.x = end.x - perpoffset.x + diroffset.x; p3.y = end.y - perpoffset.y + diroffset.y; output.push_back(p2.x); output.push_back(p2.y); output.push_back(p0.x); output.push_back(p0.y); output.push_back(p1.x); output.push_back(p1.y); output.push_back(p3.x); output.push_back(p3.y); } } The problem is that there are then gaps as seen here: http://img816.imageshack.us/img816/2882/eeekkk.png There must be a way to fix this. I see a pattern but I just cant figure it out. There must be a way to fill the missing inbetweens. Thanks

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  • trie reg exp parse step over char and continue

    - by forest.peterson
    Setup: 1) a string trie database formed from linked nodes and a vector array linking to the next node terminating in a leaf, 2) a recursive regular expression function that if A) char '*' continues down all paths until string length limit is reached, then continues down remaining string paths if valid, and B) char '?' continues down all paths for 1 char and then continues down remaining string paths if valid. 3) after reg expression the candidate strings are measured for edit distance against the 'try' string. Problem: the reg expression works fine for adding chars or swapping ? for a char but if the remaining string has an error then there is not a valid path to a terminating leaf; making the matching function redundant. I tried adding a 'step-over' ? char if the end of the node vector was reached and then followed every path of that node - allowing this step-over only once; resulted in a memory exception; I cannot find logically why it is accessing the vector out of range - bactracking? Questions: 1) how can the regular expression step over an invalid char and continue with the path? 2) why is swapping the 'sticking' char for '?' resulting in an overflow? Function: void Ontology::matchRegExpHelper(nodeT *w, string inWild, Set<string> &matchSet, string out, int level, int pos, int stepover) { if (inWild=="") { matchSet.add(out); } else { if (w->alpha.size() == pos) { int testLength = out.length() + inWild.length(); if (stepover == 0 && matchSet.size() == 0 && out.length() > 8 && testLength == tokenLength) {//candidate generator inWild[0] = '?'; matchRegExpHelper(w, inWild, matchSet, out, level, 0, stepover+1); } else return; //giveup on this path } if (inWild[0] == '?' || (inWild[0] == '*' && (out.length() + inWild.length() ) == level ) ) { //wild matchRegExpHelper(w->alpha[pos].next, inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover);//follow path -> if ontology is full, treat '*' like a '?' } else if (inWild[0] == '*') matchRegExpHelper(w->alpha[pos].next, '*'+inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover); //keep adding chars if (inWild[0] == w->alpha[pos].letter) //follow self matchRegExpHelper(w->alpha[pos].next, inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover); //follow char matchRegExpHelper(w, inWild, matchSet, out, level, pos+1, stepover);//check next path } } Error Message: +str "Attempt to access index 1 in a vector of size 1." std::basic_string<char,std::char_traits<char>,std::allocator<char> > +err {msg="Attempt to access index 1 in a vector of size 1." } ErrorException Note: this function works fine for hundreds of test strings with '*' wilds if the extra stepover gate is not used Semi-Solved: I place a pos < w->alpha.size() condition on each path that calls w->alpha[pos]... - this prevented the backtrack calls from attempting to access the vector with an out of bounds index value. Still have other issues to work out - it loops infinitely adding the ? and backtracking to remove it, then repeat. But, moving forward now. Revised question: why during backtracking is the position index accumulating and/or not deincrementing - so at somepoint it calls w->alpha[pos]... with an invalid position that is either remaining from the next node or somehow incremented pos+1 when passing upward?

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  • a question in NS c programming

    - by bahar
    Hi I added a new patch to my NS and I've seen thise two errors. Does anyone Know what I can do? error: specialization of 'bool std::less<_Tp::operator()(const _Tp&, const _Tp&) const [with _Tp = _AlgorithmTime]' in different namespace from definition of 'bool std::less<_Tp::operator()(const _Tp&, const _Tp&) const [with _Tp = _AlgorithmTime]' and the errors are from this code typedef struct _AlgorithmTime { // Round. int round; // Fase. int fase; // Valore massimo di fase. int last_fase; public: _AlgorithmTime() { round = 0; fase = 0; last_fase = 0; } // Costruttore. _AlgorithmTime(int r, int f, int l) { round = r; fase = f; last_fase = l; } // Costruttore. _AlgorithmTime(const _AlgorithmTime & t) { round = t.round; fase = t.fase; last_fase = t.last_fase; } // Operatore di uguaglianza. bool operator== (struct _AlgorithmTime & t) { return ((t.fase == fase) && (t.round == round)); } // Operatore minore. bool operator < (struct _AlgorithmTime & t) { if (round < t.round) return true; if (round > t.round) return false; if (fase < t.fase) return true; return false; } // Operatore maggiore. bool operator > (struct _AlgorithmTime & t) { if (round > t.round) return true; if (round < t.round) return false; if (fase > t.fase) return true; return false; } void operator++ () { if (fase == last_fase) { round++; fase = 0; return; } fase++; } void operator-- () { if (fase == 0) { round--; fase = last_fase; return; } fase--; } }AlgorithmTime; template< bool std::less::operator()(const AlgorithmTime & t1, const AlgorithmTime & t2)const { if (t1.round < t2.round) return true; if (t1.round t2.round) return false; if (t1.fase < t2.fase) return true; return false; } Thanks

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  • Did I implement this correctly?

    - by user146780
    I'm trying to implement line thickness as denoted here: start = line start = vector(x1, y1) end = line end = vector(x2, y2) dir = line direction = end - start = vector(x2-x1, y2-y1) ndir = normalized direction = dir*1.0/length(dir) perp = perpendicular to direction = vector(dir.x, -dir.y) nperp = normalized perpendicular = perp*1.0/length(perp) perpoffset = nperp*w*0.5 diroffset = ndir*w*0.5 p0, p1, p2, p3 = polygon points: p0 = start + perpoffset - diroffset p1 = start - perpoffset - diroffset p2 = end + perpoffset + diroffset p3 = end - perpoffset + diroffset I'v implemented this like so: void OGLENGINEFUNCTIONS::GenerateLinePoly(const std::vector<std::vector<GLdouble>> &input, std::vector<GLfloat> &output, int width) { output.clear(); float temp; float dirlen; float perplen; POINTFLOAT start; POINTFLOAT end; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; POINTFLOAT p0, p1, p2, p3; for(int i = 0; i < input.size() - 1; ++i) { start.x = input[i][0]; start.y = input[i][1]; end.x = input[i + 1][0]; end.y = input[i + 1][1]; dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = dir.x * (1.0 / dirlen); ndir.y = dir.y * (1.0 / dirlen); perp.x = dir.x; perp.y = -dir.y; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = perp.x * (1.0 / perplen); nperp.y = perp.y * (1.0 / perplen); perpoffset.x = nperp.x * width * 0.5; perpoffset.y = nperp.y * width * 0.5; diroffset.x = ndir.x * width * 0.5; diroffset.y = ndir.x * width * 0.5; // p0 = start + perpoffset - diroffset //p1 = start - perpoffset - diroffset //p2 = end + perpoffset + diroffset // p3 = end - perpoffset + diroffset p0.x = start.x + perpoffset.x - diroffset.x; p0.y = start.y + perpoffset.y - diroffset.y; p1.x = start.x - perpoffset.x - diroffset.x; p1.y = start.y - perpoffset.y - diroffset.y; p2.x = end.x + perpoffset.x + diroffset.x; p2.y = end.y + perpoffset.y + diroffset.y; p3.x = end.x - perpoffset.x + diroffset.x; p3.y = end.y - perpoffset.y + diroffset.y; output.push_back(p0.x); output.push_back(p0.y); output.push_back(p1.x); output.push_back(p1.y); output.push_back(p2.x); output.push_back(p2.y); output.push_back(p3.x); output.push_back(p3.y); } } But right now the lines look perpendicular and wrong, it should be giving me quads to render which is what i'm rendering, but the points it is outputing are strange. Have I done this wrong? Thanks

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  • [C++] Adding a string or char array to a byte vector

    - by xeross
    I'm currently working on a class to create and read out packets send through the network, so far I have it working with 16bit and 8bit integers (Well unsigned but still). Now the problem is I've tried numerous ways of copying it over but somehow the _buffer got mangled, it segfaulted, or the result was wrong. I'd appreciate if someone could show me a working example. My current code can be seen below. Thanks, Xeross Main #include <iostream> #include <stdio.h> #include "Packet.h" using namespace std; int main(int argc, char** argv) { cout << "#################################" << endl; cout << "# Internal Use Only #" << endl; cout << "# Codename PACKETSTORM #" << endl; cout << "#################################" << endl; cout << endl; Packet packet = Packet(); packet.SetOpcode(0x1f4d); cout << "Current opcode is: " << packet.GetOpcode() << endl << endl; packet.add(uint8_t(5)) .add(uint16_t(4000)) .add(uint8_t(5)); for(uint8_t i=0; i<10;i++) printf("Byte %u = %x\n", i, packet._buffer[i]); printf("\nReading them out: \n1 = %u\n2 = %u\n3 = %u\n4 = %s", packet.readUint8(), packet.readUint16(), packet.readUint8()); return 0; } Packet.h #ifndef _PACKET_H_ #define _PACKET_H_ #include <iostream> #include <vector> #include <stdio.h> #include <stdint.h> #include <string.h> using namespace std; class Packet { public: Packet() : m_opcode(0), _buffer(0), _wpos(0), _rpos(0) {} Packet(uint16_t opcode) : m_opcode(opcode), _buffer(0), _wpos(0), _rpos(0) {} uint16_t GetOpcode() { return m_opcode; } void SetOpcode(uint16_t opcode) { m_opcode = opcode; } Packet& add(uint8_t value) { if(_buffer.size() < _wpos + 1) _buffer.resize(_wpos + 1); memcpy(&_buffer[_wpos], &value, 1); _wpos += 1; return *this; } Packet& add(uint16_t value) { if(_buffer.size() < _wpos + 2) _buffer.resize(_wpos + 2); memcpy(&_buffer[_wpos], &value, 2); _wpos += 2; return *this; } uint8_t readUint8() { uint8_t result = _buffer[_rpos]; _rpos += sizeof(uint8_t); return result; } uint16_t readUint16() { uint16_t result; memcpy(&result, &_buffer[_rpos], sizeof(uint16_t)); _rpos += sizeof(uint16_t); return result; } uint16_t m_opcode; std::vector<uint8_t> _buffer; protected: size_t _wpos; // Write position size_t _rpos; // Read position }; #endif // _PACKET_H_

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  • Segmentation fault, shared library

    - by user1306184
    I get Segmentation Fault when I try to run my program. Can someone please help me find out what Im doing wrong? Compiling with this: g++ sms_out.cpp -o sms_out g++ -c -fPIC SMSDispatch.cpp g++ -shared SMSDispatch.o -o libSMSDispatch.so It should be a shared library and dynamic linking. I get Segmentation Fault when I try to run sms_out. //sms_out.cpp #include <iostream> #include<cstdlib> #include<fstream> #include<sstream> #include<string> #include "SMSDispatch.h" using namespace std; string sms = ""; void sendSMS(string sms) { SMSDispatch* sPtr=0; sPtr->sendSMS(sms); } int main(int argc, char *argv[]) { if(argv[1]) { string input = argv[1]; string test = "--author"; if(input == test) { cout << "s149113" << endl; return 0; } } string line = ""; string file = "sms_out.txt"; ifstream myfile(file.c_str()); while(getline(myfile, line)) { string idnr, landcode, number, error; istringstream linestream(line); unsigned short errorcode; //Split the sentence getline(linestream, idnr, '\t'); getline(linestream, landcode, ':'); getline(linestream, number, '\t'); getline(linestream, error); if(idnr == "") break; //Make string to int try { errorcode = atoi(error.c_str() ); } catch (exception &) { } //Put together landcode and tlfnumber string nr = landcode + number; string txt = "Thank you for your vote!"; if(errorcode == 100) txt = "Invalid question, please try again"; else if(errorcode == 110) txt = "Sorry, only one vote pr. number"; else if(errorcode == 200) txt = "Invalid alternative, please try again"; else if(errorcode == 300) txt = "Missing a statement after other, please try again"; else if(errorcode == 999) txt = "An error occurred, please try again"; sms += "{\"ID\":" + idnr + ",\"nr\":" + nr + ",\"txt\":" + "\"" + txt + "\"" + "}\n"; } cout << sms << endl; sendSMS(sms); } //SMSDispatch.h #include <string> #ifndef SMSDISPATCH_H #define SMSDISPATCH_H using namespace std; class SMSDispatch{ public: virtual void sendSMS(string json); }; #endif //SMSDispatch.cpp #include <iostream> #include <fstream> #include "SMSDispatch.h" using namespace std; /*virtual*/void SMSDispatch::sendSMS(string json) { ofstream myfile; myfile.open ("sms_out.log"); myfile << json; myfile.close(); } int main() { }

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  • Reordering Variadic Parameters

    - by void-pointer
    I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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  • Ambiguous constructor call

    - by Crystal
    I'm trying to create a simple date class, but I get an error on my main file that says, "call of overloaded Date() is ambiguous." I'm not sure why since I thought as long as I had different parameters for my constructor, I was ok. Here is my code: header file: #ifndef DATE_H #define DATE_H using std::string; class Date { public: static const int monthsPerYear = 12; // num of months in a yr Date(int = 1, int = 1, int = 1900); // default constructor Date(); // uses system time to create object void print() const; // print date in month/day/year format ~Date(); // provided to confirm destruction order string getMonth(int month) const; // gets month in text format private: int month; // 1 - 12 int day; // 1 - 31 int year; // any year int checkDay(int) const; }; #endif .cpp file #include <iostream> #include <iomanip> #include <string> #include <ctime> #include "Date.h" using namespace std; Date::Date() { time_t seconds = time(NULL); struct tm* t = localtime(&seconds); month = t->tm_mon; day = t->tm_mday; year = t->tm_year; } Date::Date(int mn, int dy, int yr) { if (mn > 0 && mn <= monthsPerYear) month = mn; else { month = 1; // invalid month set to 1 cout << "Invalid month (" << mn << ") set to 1.\n"; } year = yr; // could validate yr day = checkDay(dy); // validate the day // output Date object to show when its constructor is called cout << "Date object constructor for date "; print(); cout << endl; } void Date::print() const { string str; cout << month << '/' << day << '/' << year << '\n'; // new code for HW2 cout << setfill('0') << setw(3) << day; // prints in ddd cout << " " << year << '\n'; // yyyy format str = getMonth(month); // prints in month (full word), day, year cout << str << " " << day << ", " << year << '\n'; } and my main.cpp #include <iostream> #include "Date.h" using std::cout; int main() { Date date1(4, 30, 1980); date1.print(); cout << '\n'; Date date2; date2.print(); }

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  • c++ protected pointer member to the same class and access privileges

    - by aajmakin
    Hi, Example code is included at the bottom of the message. I'm puzzled about the protected access specifier in a class. I have define a class node which has a protected string member name string name; and a vector of node pointers vector args; Before I thought that a member function of node could not do args[0]-name but a program that does just this does compile and run. However, now I would like to inherit this class and access the name field in one of the args array pointers from this derived class args[0]-name but this does not compile. When I compile the example code below with the commented sections uncommented, the compiler reports: Compiler output: g++ test.cc -o test test.cc: In member function 'void foo::newnode::print_args2()': test.cc:22: error: 'std::string foo::node::name' is protected test.cc:61: error: within this context Compilation exited abnormally with code 1 at Thu Jun 17 12:40:12 Questions: Why can I access the name field of the node pointers in args in class node, because this is what I would excpect from a similarly defined private field in Java. How can I access those fields from the derived class. Example code: #include <iostream> #include <vector> using namespace std; namespace foo { class node; typedef std::vector<node*> nodes; class node { public: node (string _name); void print_args (); void add_node (node* a); protected: nodes args; string name; }; } foo::node::node (string _name) : args(0) { name = _name; } void foo::node::add_node (node* a) { args.push_back(a); } void foo::node::print_args () { for (int i = 0; i < args.size(); i++) { cout << "node " << i << ": " << args[i]->name << endl; } } // namespace foo // { // class newnode : public node // { // public: // newnode (string _name) : node(_name) {} // void print_args2 (); // protected: // }; // } // void foo::newnode::print_args2 () // { // for (int i = 0; i < args.size(); i++) // { // cout << "node " << i << ": " << args[i]->name << endl; // } // } int main (int argc, char** argv) { foo::node a ("a"); foo::node b ("b"); foo::node c ("c"); a.add_node (&b); a.add_node (&c); a.print_args (); // foo::newnode newa ("newa"); // foo::newnode newb ("newb"); // foo::newnode newc ("newc"); // newa.add_node (&newb); // newa.add_node (&newc); // newa.print_args2 (); return 0; }

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  • Edges on polygon outlines not always correct

    - by user146780
    I'm using the algorithm below to generate quads which are then rendered to make an outline like this http://img810.imageshack.us/img810/8530/uhohz.png The problem as seen on the image, is that sometimes the lines are too thin when they should always be the same width. My algorithm finds the 4 verticies for the first one then the top 2 verticies of the next ones are the bottom 2 of the previous. This creates connected lines, but it seems to not always work. How could I fix this? This is my algorithm: void OGLENGINEFUNCTIONS::GenerateLinePoly(const std::vector<std::vector<GLdouble>> &input, std::vector<GLfloat> &output, int width) { output.clear(); if(input.size() < 2) { return; } int temp; float dirlen; float perplen; POINTFLOAT start; POINTFLOAT end; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; POINTFLOAT p0, p1, p2, p3; for(unsigned int i = 0; i < input.size() - 1; ++i) { start.x = static_cast<float>(input[i][0]); start.y = static_cast<float>(input[i][1]); end.x = static_cast<float>(input[i + 1][0]); end.y = static_cast<float>(input[i + 1][1]); dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = static_cast<float>(dir.x * 1.0 / dirlen); ndir.y = static_cast<float>(dir.y * 1.0 / dirlen); perp.x = dir.y; perp.y = -dir.x; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = static_cast<float>(perp.x * 1.0 / perplen); nperp.y = static_cast<float>(perp.y * 1.0 / perplen); perpoffset.x = static_cast<float>(nperp.x * width * 0.5); perpoffset.y = static_cast<float>(nperp.y * width * 0.5); diroffset.x = static_cast<float>(ndir.x * 0 * 0.5); diroffset.y = static_cast<float>(ndir.y * 0 * 0.5); // p0 = start + perpoffset - diroffset //p1 = start - perpoffset - diroffset //p2 = end + perpoffset + diroffset // p3 = end - perpoffset + diroffset p0.x = start.x + perpoffset.x - diroffset.x; p0.y = start.y + perpoffset.y - diroffset.y; p1.x = start.x - perpoffset.x - diroffset.x; p1.y = start.y - perpoffset.y - diroffset.y; if(i > 0) { temp = (8 * (i - 1)); p2.x = output[temp + 2]; p2.y = output[temp + 3]; p3.x = output[temp + 4]; p3.y = output[temp + 5]; } else { p2.x = end.x + perpoffset.x + diroffset.x; p2.y = end.y + perpoffset.y + diroffset.y; p3.x = end.x - perpoffset.x + diroffset.x; p3.y = end.y - perpoffset.y + diroffset.y; } output.push_back(p2.x); output.push_back(p2.y); output.push_back(p0.x); output.push_back(p0.y); output.push_back(p1.x); output.push_back(p1.y); output.push_back(p3.x); output.push_back(p3.y); } } Thanks

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  • Debugging errors in c++

    - by user1513323
    I was working on a program that printed out the word count, character count and line count depending on the user's input. But I keep getting these error that are completely unknown to me. I was wondering if anyone could help. ** I've changed it from previous mistakes and am still receiving errors. Sorry I'm new to C++. The errors I got were filestat.cpp:47: error: ‘line’ was not declared in this scope filestat.cpp: In function ‘int wc(std::string)’: filestat.cpp:55: error: ‘line’ was not declared in this scope filestat.cpp: In function ‘int cc(std::string)’: filestat.cpp:67: error: ‘line’ was not declared in this scope #include<iostream> #include<fstream> #include<string> using namespace std; int lc(string fname); int wc(string fname); int cc(string fname); int main(){ string fname,line,command; ifstream ifs; int i; while(true){ cout<<"---- Enter a file name : "; if(getline(cin,line)){ if(line.length()== 4 && line.compare("exit")== 0){ cout<<"Exiting"; exit(0); }else{ string command = line.substr(0,2); fname= line.substr(4, line.length() -5); if( ifs.fail()){ ifs.open(fname.c_str()); cerr<< "File not found" <<fname <<endl; ifs.clear(); }else{ if(command.compare("lc")){ lc(fname); }else if (command.compare("wc")){ wc(fname); }else if(command.compare("cc")){ cc(fname); }else cout<<"Command unknown. "; } } } } return 0; } int lc(string fname){ int count; while(getline(fname, line)){ count++; } cout<<"Number of lines: "<<count ; } int wc(string fname){ int count; while(getline(fname, line)){ int pos=line.find_first_of("\n\t ",0); while(pos =! string::npos){ int length=line.length(); line = line.substr(pos+1, length - pos); count++; } } cout<< "Number of words: " <<count; } int cc(string fname){ int count; while(getline(fname, line)){ count = count + line.length(); } cout<< "Number of words: " <<count; }

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  • What common interface would be appropriate for these game object classes?

    - by Jefffrey
    Question A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Context Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place). Meaning of "hacks" in the implementation I'm referring to I'm talking about the implementations that defines Entities as simple IDs to which components are dynamically attached. Their implementation can vary from C-stylish: int last_id; Position* positions[MAX_ENTITIES]; Movement* movements[MAX_ENTITIES]; Where positions[i], movements[i], component[i], ... make up the entity. Or to more C++-style: int last_id; std::map<int, Position> positions; std::map<int, Movement> movements; From which systems can detect if an entity/id can have attached components.

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  • How to get this wavefront .obj data onto the frustum?

    - by NoobScratcher
    I've finally figured out how to get the data from a .obj file and store the vertex positions x,y,z into a structure called Points with members x y z which are of type float. I want to know how to get this data onto the screen. Here is my attempt at doing so: //make a fileobject and store list and the index of that list in a c string ifstream file (list[index].c_str() ); std::vector<int>faces; std::vector<Point>points; points.push_back(Point()); Point p; int face[4]; while ( !file.eof() ) { char modelbuffer[10000]; //Get lines and store it in line string file.getline(modelbuffer, 10000); switch(modelbuffer[0]) { case 'v' : sscanf(modelbuffer, "v %f %f %f", &p.x, &p.y, &p.z); points.push_back(p); cout << "Getting Vertex Positions" << endl; cout << "v" << p.x << endl; cout << "v" << p.y << endl; cout << "v" << p.z << endl; break; case 'f': sscanf(modelbuffer, "f %d %d %d %d", face, face+1, face+2, face+3 ); cout << face[0] << endl; cout << face[1] << endl; cout << face[2] << endl; cout << face[3] << endl; faces.push_back(face[0]); faces.push_back(face[1]); faces.push_back(face[2]); faces.push_back(face[3]); } GLuint vertexbuffer; glGenBuffers(1, &vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, points.size(), points.data(), GL_STATIC_DRAW); //glBufferData(GL_ARRAY_BUFFER,sizeof(points), &(points[0]), GL_STATIC_DRAW); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); glVertexPointer(3, GL_FLOAT, sizeof(points),points.data()); glIndexPointer(GL_DOUBLE, 0, faces.data()); glDrawArrays(GL_QUADS, 0, points.size()); glDrawElements(GL_QUADS, faces.size(), GL_UNSIGNED_INT, faces.data()); } As you can see I've clearly failed the end part but I really don't know why its not rendering the data onto the frustum? Does anyone have a solution for this?

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  • pointPolygonTest in OpenCV 2.2

    - by Mathieu Dubois
    I wanted to use pointPolygonTest but I have a problem. I'm stuck to OpenCV2.2. I tried to use the code found here: http://docs.opencv.org/doc/tutorials/imgproc/shapedescriptors/point_polygon_test/point_polygon_test.html#point-polygon-test I use findContours to detect contours in an image. Under OpenCV 2.2 returns a vector< vector<Point> >. The problem is that pointPolygonTest accept a matrix as an entry. Therefore the code doesn't compile with OpenCV 2.2: erreur: invalid initialization of reference of type ‘const cv::Mat&’ from expression of type ‘std::vector<cv::Point_<int>, std::allocator<cv::Point_<int> > >’ Under more recent OpenCV versions, the findContours function returns vector<Mat> so it's easy to pass to pointPolygonTest (see the example). I guess I could convert the vector< vector<Point> > to vector<Mat>. Unfortunately the documentation is not very clear about the format. Does anybody have an advice?

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  • comparison between string literal

    - by wiso
    This very simple code: #include <iostream> using namespace std; void exec(char* option) { cout << "option is " << option << endl; if (option == "foo") cout << "option foo"; else if (option == "bar") cout << "opzion bar"; else cout << "???"; cout << endl; } int main() { char opt[] = "foo"; exec(opt); return 0; } generate two warning: comparison with string literal results in unspecified behaviour. Can you explain why exactly this code doesn't work, but if I change char opt[] to char *opt it works, but generates the warning? Is it related to the \0 termination? What is the difference between the two declaration of opt? What if I use const qualifier? The solution is to use std::string?

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  • C++ question: boost::bind receive other boost::bind

    - by user355034
    I want to make this code work properly, what should I do? giving this error on the last line. what am I doing wrong? i know boost::bind need a type but i'm not getting. help class A { public: template <class Handle> void bindA(Handle h) { h(1, 2); } }; class B { public: void bindB(int number, int number2) { std::cout << "1 " << number << "2 " << number2 << std::endl; } }; template struct Wrap_ { Wrap_(Han h) : h_(h) {} template<typename Arg1, typename Arg2> void operator()(Arg1 arg1, Arg2 arg2) { h_(arg1, arg2); } Han h_; }; template inline Wrap_<Handler> make(Handler h) { return Wrap_<Handler> (h); } int main() { A a; B b; ((boost::bind)(&B::bindB, b, _1, _2))(1, 2); ((boost::bind)(&A::bindA, a, make(boost::bind(&B::bindB, b, _1, _2))))(); /i want compiled success and execute success this code/ }

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  • Source-to-source compiler framework wanted

    - by cheungcc_2000
    Dear all, I used to use OpenC++ (http://opencxx.sourceforge.net/opencxx/html/overview.html) to perform code generation like: Source: class MyKeyword A { public: void myMethod(inarg double x, inarg const std::vector<int>& y, outarg double& z); }; Generated: class A { public: void myMethod(const string& x, double& y); // generated method below: void _myMehtod(const string& serializedInput, string& serializedOutput) { double x; std::vector<int> y; // deserialized x and y from serializedInput double z; myMethod(x, y, z); } }; This kind of code generation directly matches the use case in the tutorial of OpenC++ (http://www.csg.is.titech.ac.jp/~chiba/opencxx/tutorial.pdf) by writing a meta-level program for handling "MyKeyword", "inarg" and "outarg" and performing the code generation. However, OpenC++ is sort of out-of-date and inactive now, and my code generator can only work on g++ 3.2 and it triggers error on parsing header files of g++ of higher version. I have looked at VivaCore, but it does not provide the infra-structure for compiling meta-level program. I'm also looking at LLVM, but I cannot find documentation that tutor me on working out my source-to-source compilation usage. I'm also aware of the ROSE compiler framework, but I'm not sure whether it suits my usage, and whether its proprietary C++ front-end binary can be used in a commercial product, and whether a Windows version is available. Any comments and pointers to specific tutorial/paper/documentation are much appreciated.

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  • Boost.Program_options fixed number of tokens

    - by kloffy
    Boost.Program_options provides a facility to pass multiple tokens via command line arguments as follows: std::vector<int> nums; po::options_description desc("Allowed options"); desc.add_options() ("help", "Produce help message.") ("nums", po::value< std::vector<int> >(&nums)->multitoken(), "Numbers.") ; po::variables_map vm; po::store(po::parse_command_line(argc, argv, desc), vm); po::notify(vm); However, what is the preferred way of accepting only a fixed number of arguments? The only solution I could come is to manually assign values: int nums[2]; po::options_description desc("Allowed options"); desc.add_options() ("help", "Produce help message.") ("nums", "Numbers.") ; po::variables_map vm; po::store(po::parse_command_line(argc, argv, desc), vm); if (vm.count("nums")) { // Assign nums } This feels a bit clumsy. Is there a better solution?

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  • Advice using leaks in instruments for noobs

    - by Gyozo Kudor
    Hello I am pretty new to iphone development. I have run my app for the first time using the "Leaks" from "Instruments". It shows me several leaks around 20 the smallest is 32 bytes and there is one with 1KB. I have followed the memory management guidelines, (i (think i) understand how and when to use release, not to use it when adding to autorelease pools, for every copy, retain, init there should be a release,... etc). I don't think I understand the output of the Leaks in instruments. What does "Responsible library" and "Responsible frame" mean. Because there are some classes and methods i never used directly. Are there any good tutorials for debugging memory leaks in instruments or other advice you can give me regarding leaks. Thanks in advance. Here are the largest 2 leaks. Leaked Object # Address Size Responsible Library Responsible Frame Malloc 1.00 KB 0x4827400 1024 CFNetwork std::vector *, std::allocator * ::reserve(unsigned long) // i have no idea what this is. Leaked Object # Address Size Responsible Library Responsible Frame Malloc 128 Bytes 5 640 UIKit UIImagePickerLoadPhotoLibraryIfNecessary // so this means UIImagePicker is leaking memory? The first leak i get Leaked Object # Address Size Responsible Library Responsible Frame Malloc 128 Bytes 0x442dfd0 128 UIKit UIKeyboardInputManagerClassForInputMode I don't understand any of those.

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  • Declaring struct in header file

    - by wrongusername
    I've been trying to include a structure called "student" in a student.h file, but I'm not quite sure how to do it. My student.h file code consists of entirely: #include<string> using namespace std; struct Student; while the student.cpp file consists of entirely: #include<string> using namespace std; struct Student { string lastName, firstName; //long list of other strings... just strings though }; Unfortunately, files that use #include "student.h" come up with numerous errors like error C2027: use of undefined type 'Student', error C2079: 'newStudent' uses undefined struct 'Student' (where newStudent is a function with a Student parameter), and error C2228: left of '.lastName' must have class/struct/union. It appears the compiler (VC++) does not recognize struct Student from "student.h" or something? I have tried declaring the whole struct in "student.h", but it didn't help either. How can I declare struct Student in "student.h" so that I can just #include "student.h" and start using the struct? BTW, it seems there are no compiler errors in student.h...

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  • Beginner question - Loop invariants (Specifically Ch.3 of "Accelerated C++")

    - by Owen
    Hi - as I said, a complete beginner question here. I'm currently working my way through "Accelerated C++" and just came across this in chapter 3: // invariant: // we have read count grades so far, and // sum is the sum of the first count grades while (cin >> x) { ++count; sum += x; } The authors follow this by explaining that the invariant needs special attention paid to it because when the input is read into the variable x, we will have read count+1 grades and thus the invariant will be untrue. Similarly, when we have incremented the counter, the variable sum will no longer be the sum of the last count grades (in case you hadn't guessed, it's the traditional program for calculating student marks). What I don't understand is why this matters. Surely for just about any other loop, a similar statement would be true? For example, here is the book's first while loop (the output is filled in later): // invariant: we have written r rows so far while (r != rows) { // write a row of output std::cout << std::endl; ++r; } Once we have written the appropriate row of output, surely the invariant is false until we have incremented r, just as in the other example? It's probably something really obvious, anyone could enlighten me as to what makes these two cases different, that'd be great - and thanks in advance for taking the time to answer such a complete novice question. Owen

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  • Multiple sendto() using UDP socket

    - by ereOn
    Hi, I have a network software which uses UDP to communicate with other instances of the same program. For different reasons, I must use UDP here. I recently had problems sending huge ammounts of data over UDP and had to implement a fragmentation system to split my messages into small data chunks. So far, it worked well but I now encounter an issue when I have to send a lot of data chunks. I have the following algorithm: Split message into small data chunks (around 1500 bytes) Iterate over the data chunks list and for each, send it using sendto() However, when I send a lot of data chunks, the receiver only gets the first 6 messages. Sometimes it misses the sixth and receives the seventh. It depends. Anyway, sendto() always indicates success. This always happen when I test my software over a loopback interface (127.0.0.1) but never over my LAN network. If I add something like std::cout << "test" << std::endl; between the sendto() then every frame is received. I am aware that UDP allows packet loss and that my frames might be loss for a lot of reasons and I suppose it has to do with the rate I am sending the data chunks at. What would be the right approach here ? Implementing some acknowledgement mechanism (just like TCP) seems overkill. Adding some arbitrary waiting time between the sendto() is ugly and will probably decrease performance. Increasing (if possible) the receiver UDP internal buffer ? I don't even know if this is possible. Something else ? I really need your advices here. Thank very much.

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