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• Why can't I sort this container?

  - by Knowing me knowing you

  Please don't mind that there is no insert fnc and that data are hardcoded. The main purpouse of it is to correctly implement iterator for this container. //file Set.h #pragma once template<class T> class Set { template<class T> friend ostream& operator<<(ostream& out, const Set<T>& obj); private: T** myData_; std::size_t mySize_; std::size_t myIndex_; public: Set(); class iterator : public std::iterator<std::random_access_iterator_tag, T*> { private: T** itData_; public: iterator(T** obj) { itData_ = obj; } T operator*() const { return **itData_; } /*Comparing values of two iterators*/ bool operator<(const iterator& obj) { return **itData_ < **obj.itData_; } /*Substracting two iterators*/ difference_type operator-(const iterator& obj) { return itData_ - obj.itData_; } /*Moving iterator backward for value*/ iterator operator-(const int value) { return itData_ - value; } /*Adding two iterators*/ difference_type operator+(const iterator& obj) { return itData_ + obj.itData_; } /*Moving iterator forward for value*/ iterator operator+(const int value) { return itData_ + value; } bool operator!=(const iterator& obj) { return (itData_ != obj.itData_); } bool operator==(const iterator& obj) { return (itData_ == obj.itData_); } T** operator++() { return ++itData_; } T** operator--() { return --itData_; } }; iterator begin() const { return myData_; } iterator end() const { return myData_ + myIndex_; } }; template<class T> ostream& operator<<(ostream& out, const Set<T>& obj) { for (int i = 0;i < 3; ++i) { out << *obj.myData_[i] << "\n"; } return out; } //file Set_impl.h #pragma once #include "stdafx.h" #include "Set.h" template<class T> Set<T>::Set() { mySize_ = 3; myIndex_ = 3; myData_ = new T*[mySize_]; myData_[0] = new T(3); myData_[1] = new T(1); myData_[2] = new T(2); } //main include "stdafx.h" #include "Set_impl.h" int _tmain(int argc, _TCHAR* argv[]) { Set<int> a; Set<int>::iterator beg_ = a.begin(); Set<int>::iterator end_ = a.end(); std::sort(beg_,end_);//WONT SORT THIS RANGE cin.get(); return 0; } Why sort can't accept this iterators even though I've provided all operators needed for sort to work? I think the best way to check what's going on is to paste this code and run it first. Thanks

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• Use of select or multithread for almost 80 or more clients?

  - by Tushar Goel

  I am working on one project in which i need to read from 80 or more clients and then write their o/p into a file continuously and then read these new data for another task. My question is what should i use select or multithreading? Also I tried to use multi threading using read/fgets and write/fputs call but as they are blocking calls and one operation can be performed at one time so it is not feasible. Any idea is much appreciated. update 1: I have tried to implement the same using condition variable. I able to achieve this but it is writing and reading one at a time.When another client tried to write then it cannot able to write unless i quit from the 1st thread. I do not understand this. This should work now. What mistake i am doing? Update 2: Thanks all .. I am able to succeeded to get this model implemented using mutex condition variable. updated Code is as below: **header file******* char *mailbox ; pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER ; pthread_cond_t writer = PTHREAD_COND_INITIALIZER; int main(int argc,char *argv[]) { pthread_t t1 , t2; pthread_attr_t attr; int fd, sock , *newfd; struct sockaddr_in cliaddr; socklen_t clilen; void *read_file(); void *update_file(); //making a server socket if((fd=make_server(atoi(argv[1])))==-1) oops("Unable to make server",1) //detaching threads pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED); ///opening thread for reading pthread_create(&t2,&attr,read_file,NULL); while(1) { clilen = sizeof(cliaddr); //accepting request sock=accept(fd,(struct sockaddr *)&cliaddr,&clilen); //error comparison against failire of request and INT if(sock==-1 && errno != EINTR) oops("accept",2) else if ( sock ==-1 && errno == EINTR) oops("Pressed INT",3) newfd = (int *)malloc(sizeof(int)); *newfd = sock; //creating thread per request pthread_create(&t1,&attr,update_file,(void *)newfd); } free(newfd); return 0; } void *read_file(void *m) { pthread_mutex_lock(&lock); while(1) { printf("Waiting for lock.\n"); pthread_cond_wait(&writer,&lock); printf("I am reading here.\n"); printf("%s",mailbox); mailbox = NULL ; pthread_cond_signal(&writer); } } void *update_file(int *m) { int sock = *m; int fs ; int nread; char buffer[BUFSIZ] ; if((fs=open("database.txt",O_RDWR))==-1) oops("Unable to open file",4) while(1) { pthread_mutex_lock(&lock); write(1,"Waiting to get writer lock.\n",29); if(mailbox != NULL) pthread_cond_wait(&writer,&lock); lseek(fs,0,SEEK_END); printf("Reading from socket.\n"); nread=read(sock,buffer,BUFSIZ); printf("Writing in file.\n"); write(fs,buffer,nread); mailbox = buffer ; pthread_cond_signal(&writer); pthread_mutex_unlock(&lock); } close(fs); }

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• Nested loop traversing arrays

  - by alecco

  There are 2 very big series of elements, the second 100 times bigger than the first. For each element of the first series, there are 0 or more elements on the second series. This can be traversed and processed with 2 nested loops. But the unpredictability of the amount of matching elements for each member of the first array makes things very, very slow. The actual processing of the 2nd series of elements involves logical and (&) and a population count. I couldn't find good optimizations using C but I am considering doing inline asm, doing rep* mov* or similar for each element of the first series and then doing the batch processing of the matching bytes of the second series, perhaps in buffers of 1MB or something. But the code would be get quite messy. Does anybody know of a better way? C preferred but x86 ASM OK too. Many thanks! Sample/demo code with simplified problem, first series are "people" and second series are "events", for clarity's sake. (the original problem is actually 100m and 10,000m entries!) #include <stdio.h> #include <stdint.h> #define PEOPLE 1000000 // 1m struct Person { uint8_t age; // Filtering condition uint8_t cnt; // Number of events for this person in E } P[PEOPLE]; // Each has 0 or more bytes with bit flags #define EVENTS 100000000 // 100m uint8_t P1[EVENTS]; // Property 1 flags uint8_t P2[EVENTS]; // Property 2 flags void init_arrays() { for (int i = 0; i < PEOPLE; i++) { // just some stuff P[i].age = i & 0x07; P[i].cnt = i % 220; // assert( sum < EVENTS ); } for (int i = 0; i < EVENTS; i++) { P1[i] = i % 7; // just some stuff P2[i] = i % 9; // just some other stuff } } int main(int argc, char *argv[]) { uint64_t sum = 0, fcur = 0; int age_filter = 7; // just some init_arrays(); // Init P, P1, P2 for (int64_t p = 0; p < PEOPLE ; p++) if (P[p].age < age_filter) for (int64_t e = 0; e < P[p].cnt ; e++, fcur++) sum += __builtin_popcount( P1[fcur] & P2[fcur] ); else fcur += P[p].cnt; // skip this person's events printf("(dummy %ld %ld)\n", sum, fcur ); return 0; } gcc -O5 -march=native -std=c99 test.c -o test

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• WTSQuerySessionInformation returning empty strings

  - by Benj

  I've written a program which should query the Terminal Services API and print out some state information about the sessions running on a terminal services box. I'm using the WTSQuerySessionInformation function to do this and it's returning some data but most of the data seems to be missing... Does anyone know why? Here's my program: void WTSGetString( HANDLE serverHandle, DWORD sessionid, WTS_INFO_CLASS command, wchar_t* commandStr) { DWORD bytesReturned = 0; LPTSTR pData = NULL; if (WTSQuerySessionInformation(serverHandle, sessionid, command, &pData, &bytesReturned)) { wprintf(L"\tWTSQuerySessionInformationW - session %d - %s returned \"%s\"\n", sessionid, commandStr, pData); } else { wprintf(L"\tWTSQuerySessionInformationW - session %d - %s failed - error=%d - ", sessionid, commandStr, GetLastError()); printLastError(NULL, GetLastError()); } WTSFreeMemory(pData); } void ExtractFromWTS( HANDLE serverHandle, DWORD sessionid ) { WTSGetString(serverHandle, sessionid, WTSInitialProgram, L"WTSInitialProgram"); WTSGetString(serverHandle, sessionid, WTSApplicationName, L"WTSApplicationName"); WTSGetString(serverHandle, sessionid, WTSWorkingDirectory, L"WTSWorkingDirectory"); WTSGetString(serverHandle, sessionid, WTSOEMId, L"WTSOEMId"); WTSGetString(serverHandle, sessionid, WTSSessionId, L"WTSSessionId"); WTSGetString(serverHandle, sessionid, WTSUserName, L"WTSUserName"); WTSGetString(serverHandle, sessionid, WTSWinStationName, L"WTSWinStationName"); WTSGetString(serverHandle, sessionid, WTSDomainName, L"WTSDomainName"); WTSGetString(serverHandle, sessionid, WTSConnectState, L"WTSConnectState"); WTSGetString(serverHandle, sessionid, WTSClientBuildNumber, L"WTSClientBuildNumber"); WTSGetString(serverHandle, sessionid, WTSClientName, L"WTSClientName"); WTSGetString(serverHandle, sessionid, WTSClientDirectory, L"WTSClientDirectory"); WTSGetString(serverHandle, sessionid, WTSClientProductId, L"WTSClientProductId"); WTSGetString(serverHandle, sessionid, WTSClientHardwareId, L"WTSClientHardwareId"); WTSGetString(serverHandle, sessionid, WTSClientAddress, L"WTSClientAddress"); WTSGetString(serverHandle, sessionid, WTSClientDisplay, L"WTSClientDisplay"); WTSGetString(serverHandle, sessionid, WTSClientProtocolType, L"WTSClientProtocolType"); } int _tmain(int argc, _TCHAR* argv[]) { PWTS_SESSION_INFOW ppSessionInfo = 0; DWORD pCount; if(!WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &ppSessionInfo, &pCount)) { printLastError(L"WTSEnumerateSessions", GetLastError()); return 1; } wprintf(L"%d WTS sessions found on host\n", pCount); for (unsigned int i=0; i<pCount; i++) { wprintf(L"> session=%d, stationName = %s\n", ppSessionInfo[i].SessionId, ppSessionInfo[i].pWinStationName); ExtractFromWTS(WTS_CURRENT_SERVER_HANDLE, ppSessionInfo[i].SessionId); LPWSTR sessionstr = new wchar_t[200]; wsprintf(sessionstr, L"%d", ppSessionInfo[i].SessionId); } return 0; } And here's the output: C:\Users\Administrator\Desktop>ObtainWTSStartShell.exe empserver1 4 WTS sessions found on host > session=0, stationName = Services WTSQuerySessionInformationW - session 0 - WTSInitialProgram failed - error=87 - The paramete r is incorrect. WTSQuerySessionInformationW - session 0 - WTSApplicationName failed - error=87 - The paramet er is incorrect. WTSQuerySessionInformationW - session 0 - WTSWorkingDirectory returned "" WTSQuerySessionInformationW - session 0 - WTSOEMId returned "" WTSQuerySessionInformationW - session 0 - WTSSessionId returned "" WTSQuerySessionInformationW - session 0 - WTSUserName returned "" WTSQuerySessionInformationW - session 0 - WTSWinStationName returned "Services" WTSQuerySessionInformationW - session 0 - WTSDomainName returned "" WTSQuerySessionInformationW - session 0 - WTSConnectState returned "?" WTSQuerySessionInformationW - session 0 - WTSClientBuildNumber returned "" WTSQuerySessionInformationW - session 0 - WTSClientName returned "" WTSQuerySessionInformationW - session 0 - WTSClientDirectory returned "" WTSQuerySessionInformationW - session 0 - WTSClientProductId returned "" WTSQuerySessionInformationW - session 0 - WTSClientHardwareId returned "" WTSQuerySessionInformationW - session 0 - WTSClientAddress returned "" WTSQuerySessionInformationW - session 0 - WTSClientDisplay returned "" WTSQuerySessionInformationW - session 0 - WTSClientProtocolType returned "" GetShellProcessNameFromUserPolicy - Error: Unable to open policy key - returned [2] GetShellProcessName succeseded - explorer.exe > session=1, stationName = Console WTSQuerySessionInformationW - session 1 - WTSInitialProgram returned "" WTSQuerySessionInformationW - session 1 - WTSApplicationName returned "" WTSQuerySessionInformationW - session 1 - WTSWorkingDirectory returned "" WTSQuerySessionInformationW - session 1 - WTSOEMId returned "" WTSQuerySessionInformationW - session 1 - WTSSessionId returned "?" WTSQuerySessionInformationW - session 1 - WTSUserName returned "" WTSQuerySessionInformationW - session 1 - WTSWinStationName returned "Console" WTSQuerySessionInformationW - session 1 - WTSDomainName returned "" WTSQuerySessionInformationW - session 1 - WTSConnectState returned "?" WTSQuerySessionInformationW - session 1 - WTSClientBuildNumber returned "" WTSQuerySessionInformationW - session 1 - WTSClientName returned "" WTSQuerySessionInformationW - session 1 - WTSClientDirectory returned "" WTSQuerySessionInformationW - session 1 - WTSClientProductId returned "" WTSQuerySessionInformationW - session 1 - WTSClientHardwareId returned "" WTSQuerySessionInformationW - session 1 - WTSClientAddress returned "" WTSQuerySessionInformationW - session 1 - WTSClientDisplay returned "?" WTSQuerySessionInformationW - session 1 - WTSClientProtocolType returned "" GetShellProcessNameFromUserPolicy - Error: Unable to open policy key - returned [2] GetShellProcessName succeseded - explorer.exe > session=3, stationName = RDP-Tcp#0 WTSQuerySessionInformationW - session 3 - WTSInitialProgram returned "" WTSQuerySessionInformationW - session 3 - WTSApplicationName returned "" WTSQuerySessionInformationW - session 3 - WTSWorkingDirectory returned "" WTSQuerySessionInformationW - session 3 - WTSOEMId returned "" WTSQuerySessionInformationW - session 3 - WTSSessionId returned "?" WTSQuerySessionInformationW - session 3 - WTSUserName returned "Administrator" WTSQuerySessionInformationW - session 3 - WTSWinStationName returned "RDP-Tcp#0" WTSQuerySessionInformationW - session 3 - WTSDomainName returned "EMPSERVER1" WTSQuerySessionInformationW - session 3 - WTSConnectState returned "" WTSQuerySessionInformationW - session 3 - WTSClientBuildNumber returned "?" WTSQuerySessionInformationW - session 3 - WTSClientName returned "APWADEV03" WTSQuerySessionInformationW - session 3 - WTSClientDirectory returned "C:\Windows\System32\m stscax.dll" WTSQuerySessionInformationW - session 3 - WTSClientProductId returned "?" WTSQuerySessionInformationW - session 3 - WTSClientHardwareId returned "" WTSQuerySessionInformationW - session 3 - WTSClientAddress returned "?" WTSQuerySessionInformationW - session 3 - WTSClientDisplay returned "?" WTSQuerySessionInformationW - session 3 - WTSClientProtocolType returned "?" GetShellProcessNameFromUserPolicy - Error: Unable to open policy key - returned [2] GetShellProcessName succeseded - explorer.exe > session=65536, stationName = RDP-Tcp WTSQuerySessionInformationW - session 65536 - WTSInitialProgram returned "" WTSQuerySessionInformationW - session 65536 - WTSApplicationName returned "" WTSQuerySessionInformationW - session 65536 - WTSWorkingDirectory returned "" WTSQuerySessionInformationW - session 65536 - WTSOEMId returned "" WTSQuerySessionInformationW - session 65536 - WTSSessionId returned "" WTSQuerySessionInformationW - session 65536 - WTSUserName returned "" WTSQuerySessionInformationW - session 65536 - WTSWinStationName returned "RDP-Tcp" WTSQuerySessionInformationW - session 65536 - WTSDomainName returned "" WTSQuerySessionInformationW - session 65536 - WTSConnectState returned "?" WTSQuerySessionInformationW - session 65536 - WTSClientBuildNumber returned "" WTSQuerySessionInformationW - session 65536 - WTSClientName returned "" WTSQuerySessionInformationW - session 65536 - WTSClientDirectory returned "" WTSQuerySessionInformationW - session 65536 - WTSClientProductId returned "" WTSQuerySessionInformationW - session 65536 - WTSClientHardwareId returned "" WTSQuerySessionInformationW - session 65536 - WTSClientAddress returned "" WTSQuerySessionInformationW - session 65536 - WTSClientDisplay returned "" WTSQuerySessionInformationW - session 65536 - WTSClientProtocolType returned "" GetShellProcessNameFromUserPolicy - Error: Unable to open policy key - returned [2] GetShellProcessName succeseded - explorer.exe As you can see, some of the data looks valid, but not all....

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• Thread scheduling Round Robin / scheduling dispatch

  - by MRP

  #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <semaphore.h> #define NUM_THREADS 4 #define COUNT_LIMIT 13 int done = 0; int count = 0; int quantum = 2; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,7}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void * inc_count(void * arg); static sem_t count_sem; int quit = 0; ///////// Inc_Count//////////////// void *inc_count(void *t) { long my_id = (long)t; int i; sem_wait(&count_sem); /////////////CRIT SECTION////////////////////////////////// printf("run_thread = %d\n",my_id); printf("%d \n",thread_runtime[my_id]); for( i=0; i < thread_runtime[my_id];i++) { printf("runtime= %d\n",thread_runtime[my_id]); pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n",my_id, count); pthread_mutex_unlock(&count_mutex); sleep(1) ; }//End For sem_post(&count_sem); // Next Thread Enters Crit Section pthread_exit(NULL); } /////////// Count_Watch //////////////// void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } ////////////////// Main //////////////// int main (int argc, char *argv[]) { int i; long t1=0, t2=1, t3=2, t4=3; pthread_t threads[4]; pthread_attr_t attr; sem_init(&count_sem, 0, 1); /* Initialize mutex and condition variable objects */ pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); /* For portability, explicitly create threads in a joinable state */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); /* Wait for all threads to complete */ for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); /* Clean up and exit */ pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } I am trying to learn thread scheduling, there is a lot of technical coding that I don't know. I do know in theory how it should work, but having trouble getting started in code... I know, at least I think, this program is not real time and its not meant to be. Some how I need to create a scheduler dispatch to control the threads in the order they should run... RR FCFS SJF ect. Right now I don't have a dispatcher. What I do have is semaphores/ mutex to control the threads. This code does run FCFS... and I have been trying to use semaphores to create a RR.. but having a lot of trouble. I believe it would be easier to create a dispatcher but I dont know how. I need help, I am not looking for answers just direction.. some sample code will help to understand a bit more. Thank you.

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• How to manage memory using classes in Objective-C?

  - by Flipper

  This is my first time creating an iPhone App and I am having difficulty with the memory management because I have never had to deal with it before. I have a UITableViewController and it all works fine until I try to scroll down in the simulator. It crashes saying that it cannot allocate that much memory. I have narrowed it down to where the crash is occurring: - (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { // Dequeue or create a cell UITableViewCellStyle style = UITableViewCellStyleDefault; UITableViewCell *cell = [aTableView dequeueReusableCellWithIdentifier:@"BaseCell"]; if (!cell) cell = [[[UITableViewCell alloc] initWithStyle:style reuseIdentifier:@"BaseCell"] autorelease]; NSString* crayon; // Retrieve the crayon and its color if (aTableView == self.tableView) { crayon = [[[self.sectionArray objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] getName]; } else { crayon = [FILTEREDKEYS objectAtIndex:indexPath.row]; } cell.textLabel.text = crayon; if (![crayon hasPrefix:@"White"]) cell.textLabel.textColor = [self.crayonColors objectForKey:crayon]; else cell.textLabel.textColor = [UIColor blackColor]; return cell; } Here is the getName method: - (NSString*)getName { return name; } name is defined as: @property (nonatomic, retain) NSString *name; Now sectionArray is an NSMutableArray with instances of a class that I created Term in it. Term has a method getName that returns a NSString*. The problem seems to be the part of where crayon is being set and getName is being called. I have tried adding autorelease, release, and other stuff like that but that just causes the entire app to crash before even launching. Also if I do: cell.textLabel.text = @"test"; //crayon; /*if (![crayon hasPrefix:@"White"]) cell.textLabel.textColor = [self.crayonColors objectForKey:crayon]; else cell.textLabel.textColor = [UIColor blackColor];*/ Then I get no error whatsoever and it all scrolls just fine. Thanks in advance for the help! Edit: Here is the full Log of when I try to run the app and the error it gives when it crashes: [Session started at 2010-12-29 04:23:38 -0500.] [Session started at 2010-12-29 04:23:44 -0500.] GNU gdb 6.3.50-20050815 (Apple version gdb-967) (Tue Jul 14 02:11:58 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 1429. gdb-i386-apple-darwin(1430,0x778720) malloc: * mmap(size=1420296192) failed (error code=12) error: can't allocate region ** set a breakpoint in malloc_error_break to debug gdb stack crawl at point of internal error: [ 0 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (align_down+0x0) [0x1222d8] [ 1 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (xstrvprintf+0x0) [0x12336c] [ 2 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (xmalloc+0x28) [0x12358f] [ 3 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (dyld_info_read_raw_data+0x50) [0x1659af] [ 4 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (dyld_info_read+0x1bc) [0x168a58] [ 5 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (macosx_dyld_update+0xbf) [0x168c9c] [ 6 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (macosx_solib_add+0x36b) [0x169fcc] [ 7 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (macosx_child_attach+0x478) [0x17dd11] [ 8 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (attach_command+0x5d) [0x64ec5] [ 9 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (mi_cmd_target_attach+0x4c) [0x15dbd] [ 10 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (captured_mi_execute_command+0x16d) [0x17427] [ 11 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (catch_exception+0x41) [0x7a99a] [ 12 ] /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/libexec/gdb/gdb-i386-apple-darwin (mi_execute_command+0xa9) [0x16f63] /SourceCache/gdb/gdb-967/src/gdb/utils.c:1144: internal-error: virtual memory exhausted: can't allocate 1420296192 bytes. A problem internal to GDB has been detected, further debugging may prove unreliable. The Debugger has exited with status 1.The Debugger has exited with status 1. Here is the backtrace that I get when I set the breakpoint for malloc_error_break: #0 0x0097a68c in objc_msgSend () #1 0x01785bef in -[UILabel setText:] () #2 0x000030e0 in -[TableViewController tableView:cellForRowAtIndexPath:] (self=0x421d760, _cmd=0x29cfad8, aTableView=0x4819600, indexPath=0x42190f0) at /Volumes/Main2/Enayet/TableViewController.m:99 #3 0x016cee0c in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] () #4 0x016c6a43 in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] () #5 0x016d954f in -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow] () #6 0x016d08ff in -[UITableView layoutSubviews] () #7 0x03e672b0 in -[CALayer layoutSublayers] () #8 0x03e6706f in CALayerLayoutIfNeeded () #9 0x03e668c6 in CA::Context::commit_transaction () #10 0x03e6653a in CA::Transaction::commit () #11 0x03e6e838 in CA::Transaction::observer_callback () #12 0x00b00252 in __CFRunLoopDoObservers () #13 0x00aff65f in CFRunLoopRunSpecific () #14 0x00afec48 in CFRunLoopRunInMode () #15 0x00156615 in GSEventRunModal () #16 0x001566da in GSEventRun () #17 0x01689faf in UIApplicationMain () #18 0x00002398 in main (argc=1, argv=0xbfffefb0) at /Volumes/Main2/Enayet/main.m:14

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• Help with malloc and free: Glibc detected: free(): invalid pointer

  - by nunos

  I need help with debugging this piece of code. I know the problem is in malloc and free but can't find exactly where, why and how to fix it. Please don't answer: "Use gdb" and that's it. I would use gdb to debug it, but I still don't know much about it and am still learning it, and would like to have, in the meanwhile, another solution. Thanks. #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <unistd.h> #include <string.h> #include <sys/wait.h> #include <sys/types.h> #define MAX_COMMAND_LENGTH 256 #define MAX_ARGS_NUMBER 128 #define MAX_HISTORY_NUMBER 100 #define PROMPT ">>> " int num_elems; typedef enum {false, true} bool; typedef struct { char **arg; char *infile; char *outfile; int background; } Command_Info; int parse_cmd(char *cmd_line, Command_Info *cmd_info) { char *arg; char *args[MAX_ARGS_NUMBER]; int i = 0; arg = strtok(cmd_line, " "); while (arg != NULL) { args[i] = arg; arg = strtok(NULL, " "); i++; } num_elems = i;precisa em free_mem if (num_elems == 0) return 0; cmd_info->arg = (char **) ( malloc(num_elems * sizeof(char *)) ); cmd_info->infile = NULL; cmd_info->outfile = NULL; cmd_info->background = 0; bool b_infile = false; bool b_outfile = false; int iarg = 0; for (i = 0; i < num_elems; i++) { if ( !strcmp(args[i], "<") ) { if ( b_infile || i == num_elems-1 || !strcmp(args[i+1], "<") || !strcmp(args[i+1], ">") || !strcmp(args[i+1], "&") ) return -1; i++; cmd_info->infile = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->infile, args[i]); b_infile = true; } else if (!strcmp(args[i], ">")) { if ( b_outfile || i == num_elems-1 || !strcmp(args[i+1], ">") || !strcmp(args[i+1], "<") || !strcmp(args[i+1], "&") ) return -1; i++; cmd_info->outfile = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->outfile, args[i]); b_outfile = true; } else if (!strcmp(args[i], "&")) { if ( i == 0 || i != num_elems-1 || cmd_info->background ) return -1; cmd_info->background = true; } else { cmd_info->arg[iarg] = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->arg[iarg], args[i]); iarg++; } } cmd_info->arg[iarg] = NULL; return 0; } void print_cmd(Command_Info *cmd_info) { int i; for (i = 0; cmd_info->arg[i] != NULL; i++) printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("infile=\"%s\"\n", cmd_info->infile); printf("outfile=\"%s\"\n", cmd_info->outfile); printf("background=\"%d\"\n", cmd_info->background); } void get_cmd(char* str) { fgets(str, MAX_COMMAND_LENGTH, stdin); str[strlen(str)-1] = '\0'; } pid_t exec_simple(Command_Info *cmd_info) { pid_t pid = fork(); if (pid < 0) { perror("Fork Error"); return -1; } if (pid == 0) { if ( (execvp(cmd_info->arg[0], cmd_info->arg)) == -1) { perror(cmd_info->arg[0]); exit(1); } } return pid; } void type_prompt(void) { printf("%s", PROMPT); } void syntax_error(void) { printf("msh syntax error\n"); } void free_mem(Command_Info *cmd_info) { int i; for (i = 0; cmd_info->arg[i] != NULL; i++) free(cmd_info->arg[i]); free(cmd_info->arg); free(cmd_info->infile); free(cmd_info->outfile); } int main(int argc, char* argv[]) { char cmd_line[MAX_COMMAND_LENGTH]; Command_Info cmd_info; //char* history[MAX_HISTORY_NUMBER]; while (true) { type_prompt(); get_cmd(cmd_line); if ( parse_cmd(cmd_line, &cmd_info) == -1) { syntax_error(); continue; } if (!strcmp(cmd_line, "")) continue; if (!strcmp(cmd_info.arg[0], "exit")) exit(0); pid_t pid = exec_simple(&cmd_info); waitpid(pid, NULL, 0); free_mem(&cmd_info); } return 0; }

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• C - array count, strtok, etc

  - by Pedro

  Hi... i have a little problem on my code... HI open a txt that have this: LEI;7671;Maria Albertina da silva;[email protected]; 9;8;12;9;12;11;6;15;7;11; LTCGM;6567;Artur Pereira Ribeiro;[email protected]; 6;13;14;12;11;16;14; LEI;7701;Ana Maria Carvalho;[email protected]; 8;13;11;7;14;12;11;16;14; LEI, LTCGM are the college; 7671, 6567, 7701 is student number; Maria, Artur e Ana are the students name; [email protected], ...@gmail are emails from students; the first number of every line is the total of classes that students have; after that is students school notes; example: College: LEI Number: 7671 Name: Maria Albertina da Silva email: [email protected] total of classes: 9 Classe Notes: 8 12 9 12 11 6 15 7 11. My code: typedef struct aluno{ char sigla[5];//college char numero[80];//number char nome[80];//student name char email[20];//email int total_notas;// total of classes char tot_not[40]; // total classes char notas[20];// classe notes int nota; //class notes char situacao[80]; //situation (aproved or disaproved) }ALUNO; void ordena(ALUNO*alunos, int tam)//bubble sort { int i=0; int j=0; char temp[100]; for( i=0;i<tam;i++) for(j=0;j<tam-1;j++) if(strcmp( alunos[i].sigla[j], alunos[i].sigla[j+1])>0){ strcpy(temp, alunos[i].sigla[j]); strcpy(alunos[i].sigla[j],alunos[i].sigla[j+1]); strcpy(alunos[i].sigla[j+1], temp); } } void xml(ALUNO*alunos, int tam){ FILE *fp; char linha[60];//line int soma, max, min, count;//biggest note and lowest note and students per course count float media; //media of notes fp=fopen("example.txt","r"); if(fp==NULL){ exit(1); } else{ while(!(feof(fp))){ soma=0; media=0; max=0; min=0; count=0; fgets(linha,60,fp); if(linha[0]=='L'){ if(ap_dados=strtok(linha,";")){ strcpy(alunos[i].sigla,ap_dados);//copy to struct // i need to call bubble sort here, but i don't know how printf("College: %s\n",alunos[i].sigla); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].numero,ap_dados);//copy to struct printf("number: %s\n",alunos[i].numero); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].nome, ap_dados);//copy to struct printf("name: %s\n",alunos[i].nome); if(ap_dados=strtok(NULL,";")){ strcpy(alunos[i].email, ap_dados);//copy to struct printf("email: %s\n",alunos[i].email); } } } }i++; } if(isdigit(linha[0])){ if(info_notas=strtok(linha,";")){ strcpy(alunos[i].tot_not,info_notas); alunos[i].total_notas=atoi(alunos[i].tot_not);//total classes for(z=0;z<=alunos[i].total_notas;z++){ if(info_notas=strtok(NULL,";")){ strcpy(alunos[i].notas,info_notas); alunos[i].nota=atoi(alunos[i].notas); // student class notes } soma=soma + alunos[i].nota; media=soma/alunos[i].total_notas;//doesn't work if(alunos[i].nota>max){ max=alunos[i].nota;;//doesn't work } else{ if(min<alunos[i].nota){ min=alunos[i].nota;;//doesn't work } } //now i need to count the numbers of students in the same college, but doesn't work /*If(strcmp(alunos[i].sigla, alunos[i+1].sigla)=0){ count ++; printf("%d\n", count); here for LEI should appear 2 students and for LTCGM appear 1, don't work }*/ //Now i need to see if student is aproved or disaproved // Student is disaproved if he gets 3 notes under 10, how can i do that? } printf("media %d\n",media); //media printf("Nota maxima %d\n",max);// biggest note printf("Nota minima %d\n",min); //lowest note }i++; } } } fclose(fp); } int main(int argc, char *argv[]){ ALUNO alunos; FILE *fp; int tam; fp=fopen(nomeFicheiro,"r"); alunos = (ALUNO*) calloc (tam, sizeof(ALUNO)); xml(alunos,nomeFicheiro, tam); system("PAUSE"); return 0; }

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• Parsing "true" and "false" using Boost.Spirit.Lex and Boost.Spirit.Qi

  - by Andrew Ross

  As the first stage of a larger grammar using Boost.Spirit I'm trying to parse "true" and "false" to produce the corresponding bool values, true and false. I'm using Spirit.Lex to tokenize the input and have a working implementation for integer and floating point literals (including those expressed in a relaxed scientific notation), exposing int and float attributes. Token definitions #include <boost/spirit/include/lex_lexertl.hpp> namespace lex = boost::spirit::lex; typedef boost::mpl::vector<int, float, bool> token_value_type; template <typename Lexer> struct basic_literal_tokens : lex::lexer<Lexer> { basic_literal_tokens() { this->self.add_pattern("INT", "[-+]?[0-9]+"); int_literal = "{INT}"; // To be lexed as a float a numeric literal must have a decimal point // or include an exponent, otherwise it will be considered an integer. float_literal = "{INT}(((\\.[0-9]+)([eE]{INT})?)|([eE]{INT}))"; literal_true = "true"; literal_false = "false"; this->self = literal_true | literal_false | float_literal | int_literal; } lex::token_def<int> int_literal; lex::token_def<float> float_literal; lex::token_def<bool> literal_true, literal_false; }; Testing parsing of float literals My real implementation uses Boost.Test, but this is a self-contained example. #include <string> #include <iostream> #include <cmath> #include <cstdlib> #include <limits> bool parse_and_check_float(std::string const & input, float expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); float actual; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, basic_literal_lexer.float_literal, actual); return result && std::abs(expected - actual) < std::numeric_limits<float>::epsilon(); } int main(int argc, char *argv[]) { if (parse_and_check_float("+31.4e-1", 3.14)) { return EXIT_SUCCESS; } else { return EXIT_FAILURE; } } Parsing "true" and "false" My problem is when trying to parse "true" and "false". This is the test code I'm using (after removing the Boost.Test parts): bool parse_and_check_bool(std::string const & input, bool expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); bool actual; lex::token_def<bool> parser = expected ? basic_literal_lexer.literal_true : basic_literal_lexer.literal_false; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, parser, actual); return result && actual == expected; } but compilation fails with: boost/spirit/home/qi/detail/assign_to.hpp: In function ‘void boost::spirit::traits::assign_to(const Iterator&, const Iterator&, Attribute&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, Attribute = bool]’: boost/spirit/home/lex/lexer/lexertl/token.hpp:434: instantiated from ‘static void boost::spirit::traits::assign_to_attribute_from_value<Attribute, boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>, void>::call(const boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>&, Attribute&) [with Attribute = bool, Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, AttributeTypes = boost::mpl::vector<int, float, bool, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, HasState = mpl_::bool_<true>]’ ... backtrace of instantiation points .... boost/spirit/home/qi/detail/assign_to.hpp:79: error: no matching function for call to ‘boost::spirit::traits::assign_to_attribute_from_iterators<bool, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, void>::call(const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, bool&)’ boost/spirit/home/qi/detail/construct.hpp:64: note: candidates are: static void boost::spirit::traits::assign_to_attribute_from_iterators<bool, Iterator, void>::call(const Iterator&, const Iterator&, char&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >] My interpretation of this is that Spirit.Qi doesn't know how to convert a string to a bool - surely that's not the case? Has anyone else done this before? If so, how?

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• C question: Padding bits in unsigned integers and bitwise operations (C89)

  - by Anonymous Question Guy

  I have a lot of code that performs bitwise operations on unsigned integers. I wrote my code with the assumption that those operations were on integers of fixed width without any padding bits. For example an array of 32 bit unsigned integers of which all 32 bits available for each integer. I'm looking to make my code more portable and I'm focused on making sure I'm C89 compliant (in this case). One of the issues that I've come across is possible padded integers. Take this extreme example, taken from the GMP manual: However on Cray vector systems it may be noted that short and int are always stored in 8 bytes (and with sizeof indicating that) but use only 32 or 46 bits. The nails feature can account for this, by passing for instance 8*sizeof(int)-INT_BIT. I've also read about this type of padding in other places. I actually read of a post on SO last night (forgive me, I don't have the link and I'm going to cite something similar from memory) where if you have, say, a double with 60 usable bits the other 4 could be used for padding and those padding bits could serve some internal purpose so they cannot be modified. So let's say for example my code is compiled on a platform where an unsigned int type is sized at 4 bytes, each byte being 8 bits, however the most significant 2 bits are padding bits. Would UINT_MAX in that case be 0x3FFFFFFF (1073741823) ? #include <stdio.h> #include <stdlib.h> /* padding bits represented by underscores */ int main( int argc, char **argv ) { unsigned int a = 0x2AAAAAAA; /* __101010101010101010101010101010 */ unsigned int b = 0x15555555; /* __010101010101010101010101010101 */ unsigned int c = a ^ b; /* ?? __111111111111111111111111111111 */ unsigned int d = c << 5; /* ?? __111111111111111111111111100000 */ unsigned int e = d >> 5; /* ?? __000001111111111111111111111111 */ printf( "a: %X\nb: %X\nc: %X\nd: %X\ne: %X\n", a, b, c, d, e ); return 0; } is it safe to XOR two integers with padding bits? wouldn't I XOR whatever the padding bits are? I can't find this behavior covered in C89. furthermore is the c var guaranteed to be 0x3FFFFFFF or if for example the two padding bits were both on in a or b would c be 0xFFFFFFFF ? same question with d and e. am i manipulating the padding bits by shifting? I would expect to see this below, assuming 32 bits with the 2 most significant bits used for padding, but I want to know if something like this is guaranteed: a: 2AAAAAAA b: 15555555 c: 3FFFFFFF d: 3FFFFFE0 e: 01FFFFFF Also are padding bits always the most significant bits or could they be the least significant bits? Thanks guys EDIT 12/19/2010 5PM EST: Christoph has answered my question. Thanks! I had also asked (above) whether padding bits are always the most significant bits. This is cited in the rationale for the C99 standard, and the answer is no. I am playing it safe and assuming the same for C89. Here is specifically what the C99 rationale says for §6.2.6.2 (Representation of Integer Types): Padding bits are user-accessible in an unsigned integer type. For example, suppose a machine uses a pair of 16-bit shorts (each with its own sign bit) to make up a 32-bit int and the sign bit of the lower short is ignored when used in this 32-bit int. Then, as a 32-bit signed int, there is a padding bit (in the middle of the 32 bits) that is ignored in determining the value of the 32-bit signed int. But, if this 32-bit item is treated as a 32-bit unsigned int, then that padding bit is visible to the user’s program. The C committee was told that there is a machine that works this way, and that is one reason that padding bits were added to C99. Footnotes 44 and 45 mention that parity bits might be padding bits. The committee does not know of any machines with user-accessible parity bits within an integer. Therefore, the committee is not aware of any machines that treat parity bits as padding bits. EDIT 12/28/2010 3PM EST: I found an interesting discussion on comp.lang.c from a few months ago. Bitwise Operator Effects on Padding Bits (VelocityReviews reader) Bitwise Operator Effects on Padding Bits (Google Groups alternate link) One point made by Dietmar which I found interesting: Let's note that padding bits are not necessary for the existence of trap representations; combinations of value bits which do not represent a value of the object type would also do.

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• NSStream sockets missing data

  - by Chris T.

  I am trying to pull some sample data from FreeDB as a proof of concept, but I am having a tough time retrieving all of the data off the incoming stream (I am only getting the last bits for the final query listed here (if handshakeCode = 3) I think this may be something with the threading on the main runloop, but I am not sure. Odd thing is when the buffer size is larger than 1-2 bytes (which works as expected), I seem to be losing access to the data programmatically (the totalOutput variable on the first set of data is incomplete). I set up a packet capture, and it looks like those 1024 bytes are coming across the wire, but the app just isn't working with it. It looks like the next event is coming through and basically taking over. I tried using an NSLock to no avail as well. If I drop the buffer size down to 1 or 2, things seem to be reading just fine. This is probably obvious to someone who does this all the time, but this is my first foray into this with something I am familiar with, technology wise in other languages / platforms. The following code will show you what is happening. Run with the buffer set to 1024, and you will see a short final string, but once you set it to 1, you will see the amount of data I was expecting (I was even expecting it to be split, so that's not a big worry) #import <Foundation/Foundation.h> #import <Cocoa/Cocoa.h> //STACK OVERFLOW CODE: @interface stackoverflow : NSObject <NSStreamDelegate> { NSInputStream *iStream; NSOutputStream *oStream; int handshakeCode; NSString *selectedDiscId; NSString *selectedGenre; } -(void)getMatchesFromFreeDB; -(void)sendToOutputStream:(NSString*)command; @end @implementation stackoverflow -(void)getMatchesFromFreeDB { NSHost *host = [NSHost hostWithName:@"freedb.freedb.org"]; [NSStream getStreamsToHost:host port:8880 inputStream:&iStream outputStream:&oStream]; [iStream retain]; [oStream retain]; [iStream setDelegate:self]; [oStream setDelegate:self]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [iStream open]; [oStream open]; handshakeCode = 0; //not done any processing } -(void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode { switch(eventCode) { case NSStreamEventOpenCompleted: { NSLog(@"Stream open completed"); break; } case NSStreamEventHasBytesAvailable: { NSLog(@"Stream has bytes available"); if (aStream == iStream) { NSMutableString *totalOutput = [NSMutableString stringWithString:@""]; //read data uint8_t buffer[1024]; int len; while ([iStream hasBytesAvailable]) { len = [iStream read:buffer maxLength:sizeof(buffer)]; if (len 0) { NSString *output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSUTF8StringEncoding]; //this could have also been put into an NSData object if (nil != output) { //append to the total output [totalOutput appendString:output]; } } } NSLog(@"OUTPUT , %i:\n\n%@", [totalOutput lengthOfBytesUsingEncoding:NSUTF8StringEncoding], totalOutput); NSArray *outputComponents = [totalOutput componentsSeparatedByString:@" "]; //Attempt to get handshake code, since we haven't done it yet: if (handshakeCode == 1) { //we are just getting the sign-on banner: //let's move on: handshakeCode = 2; } else if (handshakeCode == 2) { handshakeCode = [[outputComponents objectAtIndex:0] intValue]; if (handshakeCode == 200) { NSLog(@"---Handshake OK %i", handshakeCode); NSMutableString *query = [NSMutableString stringWithString:@"cddb query f3114b11 17 225 19915 36489 54850 69425 87025 103948 123242 136075 152817 178335 192850 211677 235104 262090 284882 308658 4430\n"]; handshakeCode = 3; [self sendToOutputStream:query]; } } else if (handshakeCode == 3) { //now, we are reading out the matches: if ([[outputComponents objectAtIndex:0] intValue] == 200) //found exact match: { NSLog(@"Found exact match"); selectedGenre = [outputComponents objectAtIndex:1] ; selectedDiscId = [outputComponents objectAtIndex:2]; if (selectedGenre && selectedDiscId) { //send off the request to get the entry: NSString *query = [NSString stringWithFormat:@"cddb read %@ %@\n", selectedGenre, selectedDiscId]; [self sendToOutputStream:query]; handshakeCode = 4; } } } } break; } case NSStreamEventEndEncountered: { NSLog(@"Stream event end encountered"); break; } case NSStreamEventErrorOccurred: { NSLog(@"Stream error occurred"); break; } case NSStreamEventHasSpaceAvailable: { NSLog(@"Stream has space available"); if (aStream == oStream) { if (handshakeCode == 0) { handshakeCode = 1; [self sendToOutputStream:@"cddb hello stackoverflow localhost.localdomain test .01BETA\n"]; } } break; } } } -(void)sendToOutputStream:(NSString*)command { const uint8_t *rawCommand = (const uint8_t *)[command UTF8String]; [oStream write:rawCommand maxLength:strlen(rawCommand)]; NSLog(@"Sent command: %@",command); } @end int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; stackoverflow *test = [[stackoverflow alloc] init]; [test getMatchesFromFreeDB]; NSRunLoop *runLoop = [NSRunLoop currentRunLoop]; [runLoop run]; [pool drain]; return 0; } Any help is much appreciated! Thanks

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• [ebp + 6] instead of +8 in a JIT compiler

  - by David Titarenco

  I'm implementing a simplistic JIT compiler in a VM I'm writing for fun (mostly to learn more about language design) and I'm getting some weird behavior, maybe someone can tell me why. First I define a JIT "prototype" both for C and C++: #ifdef __cplusplus typedef void* (*_JIT_METHOD) (...); #else typedef (*_JIT_METHOD) (); #endif I have a compile() function that will compile stuff into ASM and stick it somewhere in memory: void* compile (void* something) { // grab some memory unsigned char* buffer = (unsigned char*) malloc (1024); // xor eax, eax // inc eax // inc eax // inc eax // ret -> eax should be 3 /* WORKS! buffer[0] = 0x67; buffer[1] = 0x31; buffer[2] = 0xC0; buffer[3] = 0x67; buffer[4] = 0x40; buffer[5] = 0x67; buffer[6] = 0x40; buffer[7] = 0x67; buffer[8] = 0x40; buffer[9] = 0xC3; */ // xor eax, eax // mov eax, 9 // ret 4 -> eax should be 9 /* WORKS! buffer[0] = 0x67; buffer[1] = 0x31; buffer[2] = 0xC0; buffer[3] = 0x67; buffer[4] = 0xB8; buffer[5] = 0x09; buffer[6] = 0x00; buffer[7] = 0x00; buffer[8] = 0x00; buffer[9] = 0xC3; */ // push ebp // mov ebp, esp // mov eax, [ebp + 6] ; wtf? shouldn't this be [ebp + 8]!? // mov esp, ebp // pop ebp // ret -> eax should be the first value sent to the function /* WORKS! */ buffer[0] = 0x66; buffer[1] = 0x55; buffer[2] = 0x66; buffer[3] = 0x89; buffer[4] = 0xE5; buffer[5] = 0x66; buffer[6] = 0x66; buffer[7] = 0x8B; buffer[8] = 0x45; buffer[9] = 0x06; buffer[10] = 0x66; buffer[11] = 0x89; buffer[12] = 0xEC; buffer[13] = 0x66; buffer[14] = 0x5D; buffer[15] = 0xC3; // mov eax, 5 // add eax, ecx // ret -> eax should be 50 /* WORKS! buffer[0] = 0x67; buffer[1] = 0xB8; buffer[2] = 0x05; buffer[3] = 0x00; buffer[4] = 0x00; buffer[5] = 0x00; buffer[6] = 0x66; buffer[7] = 0x01; buffer[8] = 0xC8; buffer[9] = 0xC3; */ return buffer; } And finally I have the main chunk of the program: void main (int argc, char **args) { DWORD oldProtect = (DWORD) NULL; int i = 667, j = 1, k = 5, l = 0; // generate some arbitrary function _JIT_METHOD someFunc = (_JIT_METHOD) compile(NULL); // windows only #if defined _WIN64 || defined _WIN32 // set memory permissions and flush CPU code cache VirtualProtect(someFunc,1024,PAGE_EXECUTE_READWRITE, &oldProtect); FlushInstructionCache(GetCurrentProcess(), someFunc, 1024); #endif // this asm just for some debugging/testing purposes __asm mov ecx, i // run compiled function (from wherever *someFunc is pointing to) l = (int)someFunc(i, k); // did it work? printf("result: %d", l); free (someFunc); _getch(); } As you can see, the compile() function has a couple of tests I ran to make sure I get expected results, and pretty much everything works but I have a question... On most tutorials or documentation resources, to get the first value of a function passed (in the case of ints) you do [ebp+8], the second [ebp+12] and so forth. For some reason, I have to do [ebp+6] then [ebp+10] and so forth. Could anyone tell me why?

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• Why does this XML validation via XSD fail in libxml2 (but succeed in xmllint) and how do I fix it?

  - by mtree

  If I run this XML validation via xmllint: xmllint --noout --schema schema.xsd test.xml I get this success message: .../test.xml validates However if I run the same validation via libxml2's C API: int result = xmlSchemaValidateDoc(...) I get a return value of 1845 and this failure message: Element '{http://example.com/XMLSchema/1.0}foo': No matching global declaration available for the validation root. Which I can make absolutely no sense of. :( schema.xsd: <?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE xs:schema PUBLIC "-//W3C//DTD XMLSCHEMA 200102//EN" "XMLSchema.dtd" > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://example.com/XMLSchema/1.0" targetNamespace="http://example.com/XMLSchema/1.0" elementFormDefault="qualified" attributeFormDefault="unqualified"> <xs:element name="foo"> </xs:element> </xs:schema> test.xml: <?xml version="1.0" encoding="UTF-8"?> <foo xmlns="http://example.com/XMLSchema/1.0"> </foo> main.c: #include <stdio.h> #include <sys/stat.h> #include <sys/types.h> #include <string.h> #include <libxml/parser.h> #include <libxml/valid.h> #include <libxml/xmlschemas.h> u_int32_t get_file_size(const char *file_name) { struct stat buf; if ( stat(file_name, &buf) != 0 ) return(0); return (unsigned int)buf.st_size; } void handleValidationError(void *ctx, const char *format, ...) { char *errMsg; va_list args; va_start(args, format); vasprintf(&errMsg, format, args); va_end(args); fprintf(stderr, "Validation Error: %s", errMsg); free(errMsg); } int main (int argc, const char * argv[]) { const char *xsdPath = argv[1]; const char *xmlPath = argv[2]; printf("\n"); printf("XSD File: %s\n", xsdPath); printf("XML File: %s\n", xmlPath); int xmlLength = get_file_size(xmlPath); char *xmlSource = (char *)malloc(sizeof(char) * xmlLength); FILE *p = fopen(xmlPath, "r"); char c; unsigned int i = 0; while ((c = fgetc(p)) != EOF) { xmlSource[i++] = c; } printf("\n"); printf("XML Source:\n\n%s\n", xmlSource); fclose(p); printf("\n"); int result = 42; xmlSchemaParserCtxtPtr parserCtxt = NULL; xmlSchemaPtr schema = NULL; xmlSchemaValidCtxtPtr validCtxt = NULL; xmlDocPtr xmlDocumentPointer = xmlParseMemory(xmlSource, xmlLength); parserCtxt = xmlSchemaNewParserCtxt(xsdPath); if (parserCtxt == NULL) { fprintf(stderr, "Could not create XSD schema parsing context.\n"); goto leave; } schema = xmlSchemaParse(parserCtxt); if (schema == NULL) { fprintf(stderr, "Could not parse XSD schema.\n"); goto leave; } validCtxt = xmlSchemaNewValidCtxt(schema); if (!validCtxt) { fprintf(stderr, "Could not create XSD schema validation context.\n"); goto leave; } xmlSetStructuredErrorFunc(NULL, NULL); xmlSetGenericErrorFunc(NULL, handleValidationError); xmlThrDefSetStructuredErrorFunc(NULL, NULL); xmlThrDefSetGenericErrorFunc(NULL, handleValidationError); result = xmlSchemaValidateDoc(validCtxt, xmlDocumentPointer); leave: if (parserCtxt) { xmlSchemaFreeParserCtxt(parserCtxt); } if (schema) { xmlSchemaFree(schema); } if (validCtxt) { xmlSchemaFreeValidCtxt(validCtxt); } printf("\n"); printf("Validation successful: %s (result: %d)\n", (result == 0) ? "YES" : "NO", result); return 0; } console output: XSD File: /Users/dephiniteloop/Desktop/xml_validate/schema.xsd XML File: /Users/dephiniteloop/Desktop/xml_validate/test.gkml XML Source: <?xml version="1.0" encoding="UTF-8"?> <foo xmlns="http://example.com/XMLSchema/1.0"> </foo> Validation Error: Element '{http://example.com/XMLSchema/1.0}foo': No matching global declaration available for the validation root. Validation successful: NO (result: 1845) In case it matters: I'm on OSX 10.6.7 with its default libxml2.dylib (/Developer/SDKs/MacOSX10.6.sdk/usr/lib/libxml2.2.7.3.dylib)

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• Thread scheduling C

  - by MRP

  include <pthread.h> include <stdio.h> include <stdlib.h> #define NUM_THREADS 4 #define TCOUNT 5 #define COUNT_LIMIT 13 int done = 0; int count = 0; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,1}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void *inc_count(void *t) { int i; long my_id = (long)t; long run_time = thread_runtime[my_id]; if (my_id==2 && done ==0) { for(i=0; i< 5 ; i++) { if( i==4 ){done =1;} pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } if (my_id==3 && done==1) { for(i=0; i< 4 ; i++) { if(i == 3 ){ done = 2;} pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } if (my_id==4&& done == 2) { for(i=0; i< 8 ; i++) { pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n",my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } pthread_exit(NULL); } void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); count += 125; printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } int main (int argc, char *argv[]) { int i, rc; long t1=1, t2=2, t3=3, t4=4; pthread_t threads[4]; pthread_attr_t attr; pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } so this code creates 4 threads. thread 1 keeps track of the count value while the other 3 increment the count value. the run time is the number of times the thread will increment the count value. I have a done value that allows the first thread to increment the count value first until its run time is up.. so its like a First Come First Serve. my question is, is there a better way of implementing this? I have read about SCHED_FIFO or SCHED_RR.. I guess I dont know how to implement them into this code or if it can be.

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• Flex/bison, error: undeclared

  - by Imran

  hallo, i have a problem, the followed program gives back an error, error:: Undeclared(first use in function), why this error appears all tokens are declared, but this error comes, can anyone help me, here are the lex and yac files.thanks lex: %{ int yylinenu= 1; int yycolno= 1; %} %x STR DIGIT [0-9] ALPHA [a-zA-Z] ID {ALPHA}(_?({ALPHA}|{DIGIT}))*_? GROUPED_NUMBER ({DIGIT}{1,3})(\.{DIGIT}{3})* SIMPLE_NUMBER {DIGIT}+ NUMMER {GROUPED_NUMBER}|{SIMPLE_NUMBER} %% <INITIAL>{ [\n] {++yylinenu ; yycolno=1;} [ ]+ {yycolno=yycolno+yyleng;} [\t]+ {yycolno=yycolno+(yyleng*8);} "*" {return MAL;} "+" {return PLUS;} "-" {return MINUS;} "/" {return SLASH;} "(" {return LINKEKLAMMER;} ")" {return RECHTEKLAMMER;} "{" {return LINKEGESCHWEIFTEKLAMMER;} "}" {return RECHTEGESCHEIFTEKLAMMER;} "=" {return GLEICH;} "==" {return GLEICHVERGLEICH;} "!=" {return UNGLEICH;} "<" {return KLEINER;} ">" {return GROSSER;} "<=" {return KLEINERGLEICH;} ">=" {return GROSSERGLEICH;} "while" {return WHILE;} "if" {return IF;} "else" {return ELSE;} "printf" {return PRINTF;} ";" {return SEMIKOLON;} \/\/[^\n]* { ;} {NUMMER} {return NUMBER;} {ID} {return IDENTIFIER;} \" {BEGIN(STR);} . {;} } <STR>{ \n {++yylinenu ;yycolno=1;} ([^\"\\]|"\\t"|"\\n"|"\\r"|"\\b"|"\\\"")+ {return STRING;} \" {BEGIN(INITIAL);} } %% yywrap() { } YACC: %{ #include stdio.h> #include string.h> #include "lex.yy.c" void yyerror(char *err); int error=0,linecnt=1; %} %token IDENTIFIER NUMBER STRING COMMENT PLUS MINUS MAL SLASH LINKEKLAMMER RECHTEKLAMMER LINKEGESCHWEIFTEKLAMMER RECHTEGESCHEIFTEKLAMMER GLEICH GLEICHVERGLEICH UNGLEICH GROSSER KLEINER GROSSERGLEICH KLEINERGLEICH IF ELSE WHILE PRINTF SEMIKOLON %start Stmts %% Stmts : Stmt {puts("\t\tStmts : Stmt");} |Stmt Stmts {puts("\t\tStmts : Stmt Stmts");} ; //NEUE REGEL---------------------------------------------- Stmt : LINKEGESCHWEIFTEKLAMMER Stmts RECHTEGESCHEIFTEKLAMMER {puts("\t\tStmt : '{' Stmts '}'");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : '(' Cond ')' Stmt");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt ELSE Stmt {puts("\t\tStmt : '(' Cond ')' Stmt 'ELSE' Stmt");} |WHILE LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : 'PRINTF' Expr ';'");} |PRINTF Expr SEMIKOLON {puts("\t\tStmt : 'PRINTF' Expr ';'");} |IDENTIFIER GLEICH Expr SEMIKOLON {puts("\t\tStmt : 'IDENTIFIER' '=' Expr ';'");} |SEMIKOLON {puts("\t\tStmt : ';'");} ;//NEUE REGEL --------------------------------------------- Cond: Expr GLEICHVERGLEICH Expr {puts("\t\tCond : '==' Expr");} |Expr UNGLEICH Expr {puts("\t\tCond : '!=' Expr");} |Expr KLEINER Expr {puts("\t\tCond : '<' Expr");} |Expr KLEINERGLEICH Expr {puts("\t\tCond : '<=' Expr");} |Expr GROSSER Expr {puts("\t\tCond : '>' Expr");} |Expr GROSSERGLEICH Expr {puts("\t\tCond : '>=' Expr");} ;//NEUE REGEL -------------------------------------------- Expr:Term {puts("\t\tExpr : Term");} |Term PLUS Expr {puts("\t\tExpr : Term '+' Expr");} |Term MINUS Expr {puts("\t\tExpr : Term '-' Expr");} ;//NEUE REGEL -------------------------------------------- Term:Factor {puts("\t\tTerm : Factor");} |Factor MAL Term {puts("\t\tTerm : Factor '*' Term");} |Factor SLASH Term {puts("\t\tTerm : Factor '/' Term");} ;//NEUE REGEL -------------------------------------------- Factor:SimpleExpr {puts("\t\tFactor : SimpleExpr");} |MINUS SimpleExpr {puts("\t\tFactor : '-' SimpleExpr");} ;//NEUE REGEL -------------------------------------------- SimpleExpr:LINKEKLAMMER Expr RECHTEKLAMMER {puts("\t\tSimpleExpr : '(' Expr ')'");} |IDENTIFIER {puts("\t\tSimpleExpr : 'IDENTIFIER'");} |NUMBER {puts("\t\tSimpleExpr : 'NUMBER'");} |STRING {puts("\t\tSimpleExpr : 'String'");} ;//ENDE ------------------------------------------------- %% void yyerror(char *msg) { error=1; printf("Line: %d , Column: %d : %s \n", yylinenu, yycolno,yytext, msg); } int main(int argc, char *argv[]) { int val; while(yylex()) { printf("\n",yytext); } return yyparse(); }

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• "The usage of semaphores is subtly wrong"

  - by Hoonose

  This past semester I was taking an OS practicum in C, in which the first project involved making a threads package, then writing a multiple producer-consumer program to demonstrate the functionality. However, after getting grading feedback, I lost points for "The usage of semaphores is subtly wrong" and "The program assumes preemption (e.g. uses yield to change control)" (We started with a non-preemptive threads package then added preemption later. Note that the comment and example contradict each other. I believe it doesn't assume either, and would work in both environments). This has been bugging me for a long time - the course staff was kind of overwhelmed, so I couldn't ask them what's wrong with this over the semester. I've spent a long time thinking about this and I can't see the issues. If anyone could take a look and point out the error, or reassure me that there actually isn't a problem, I'd really appreciate it. I believe the syntax should be pretty standard in terms of the thread package functions (minithreads and semaphores), but let me know if anything is confusing. #include <stdio.h> #include <stdlib.h> #include "minithread.h" #include "synch.h" #define BUFFER_SIZE 16 #define MAXCOUNT 100 int buffer[BUFFER_SIZE]; int size, head, tail; int count = 1; int out = 0; int toadd = 0; int toremove = 0; semaphore_t empty; semaphore_t full; semaphore_t count_lock; // Semaphore to keep a lock on the // global variables for maintaining the counts /* Method to handle the working of a student * The ID of a student is the corresponding minithread_id */ int student(int total_burgers) { int n, i; semaphore_P(count_lock); while ((out+toremove) < arg) { n = genintrand(BUFFER_SIZE); n = (n <= total_burgers - (out + toremove)) ? n : total_burgers - (out + toremove); printf("Student %d wants to get %d burgers ...\n", minithread_id(), n); toremove += n; semaphore_V(count_lock); for (i=0; i<n; i++) { semaphore_P(empty); out = buffer[tail]; printf("Student %d is taking burger %d.\n", minithread_id(), out); tail = (tail + 1) % BUFFER_SIZE; size--; toremove--; semaphore_V(full); } semaphore_P(count_lock); } semaphore_V(count_lock); printf("Student %d is done.\n", minithread_id()); return 0; } /* Method to handle the working of a cook * The ID of a cook is the corresponding minithread_id */ int cook(int total_burgers) { int n, i; printf("Creating Cook %d\n",minithread_id()); semaphore_P(count_lock); while ((count+toadd) <= arg) { n = genintrand(BUFFER_SIZE); n = (n <= total_burgers - (count + toadd) + 1) ? n : total_burgers - (count + toadd) + 1; printf("Cook %d wants to put %d burgers into the burger stack ...\n", minithread_id(),n); toadd += n; semaphore_V(count_lock); for (i=0; i<n; i++) { semaphore_P(full); printf("Cook %d is putting burger %d into the burger stack.\n", minithread_id(), count); buffer[head] = count++; head = (head + 1) % BUFFER_SIZE; size++; toadd--; semaphore_V(empty); } semaphore_P(count_lock); } semaphore_V(count_lock); printf("Cook %d is done.\n", minithread_id()); return 0; } /* Method to create our multiple producers and consumers * and start their respective threads by fork */ void starter(int* c){ int i; for (i=0;i<c[2];i++){ minithread_fork(cook, c[0]); } for (i=0;i<c[1];i++){ minithread_fork(student, c[0]); } } /* The arguments are passed as command line parameters * argv[1] is the no of students * argv[2] is the no of cooks */ void main(int argc, char *argv[]) { int pass_args[3]; pass_args[0] = MAXCOUNT; pass_args[1] = atoi(argv[1]); pass_args[2] = atoi(argv[2]); size = head = tail = 0; empty = semaphore_create(); semaphore_initialize(empty, 0); full = semaphore_create(); semaphore_initialize(full, BUFFER_SIZE); count_lock = semaphore_create(); semaphore_initialize(count_lock, 1); minithread_system_initialize(starter, pass_args); }

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• Singleton code linker errors in vc 9.0. Runs fine in linux compiled with gcc

  - by user306560

  I have a simple logger that is implemented as a singleton. It works like i want when I compile and run it with g++ in linux but when I compile in Visual Studio 9.0 with vc++ I get the following errors. Is there a way to fix this? I don't mind changing the logger class around, but I would like to avoid changing how it is called. 1>Linking... 1>loggerTest.obj : error LNK2005: "public: static class Logger * __cdecl Logger::getInstance(void)" (?getInstance@Logger@@SAPAV1@XZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::log(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?log@Logger@@QAEXABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::closeLog(void)" (?closeLog@Logger@@QAEXXZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "private: static class Logger * Logger::_instance" (?_instance@Logger@@0PAV1@A) already defined in Logger.obj 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) The code, three files Logger.h Logger.cpp test.cpp #ifndef __LOGGER_CPP__ #define __LOGGER_CPP__ #include "Logger.h" Logger* Logger::_instance = 0; //string Logger::_path = "log"; //ofstream Logger::_log; //boost::mutex Logger::_mutex; Logger* Logger::getInstance(){ { boost::mutex::scoped_lock lock(_mutex); if(_instance == 0) { _instance = new Logger; _path = "log"; } } //mutex return _instance; } void Logger::log(const std::string& msg){ { boost::mutex::scoped_lock lock(_mutex); if(!_log.is_open()){ _log.open(_path.c_str()); } if(_log.is_open()){ _log << msg.c_str() << std::endl; } } } void Logger::closeLog(){ Logger::_log.close(); } #endif ` ... #ifndef __LOGGER_H__ #define __LOGGER_H__ #include <iostream> #include <string> #include <fstream> #include <boost/thread/mutex.hpp> #include <boost/thread.hpp> using namespace std; class Logger { public: static Logger* getInstance(); void log(const std::string& msg); void closeLog(); protected: Logger(){} private: static Logger* _instance; static string _path; static bool _logOpen; static ofstream _log; static boost::mutex _mutex; //check mutable }; #endif test.cpp ` #include <iostream> #include "Logger.cpp" using namespace std; int main(int argc, char *argv[]) { Logger* log = Logger::getInstance(); log->log("hello world\n"); return 0; }

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• Unknown error in Producer/Consumer program, believe it to be an infinite loop.

  - by ray2k

  Hello, I am writing a program that is solving the producer/consumer problem, specifically the bounded-buffer version(i believe they mean the same thing). The producer will be generating x number of random numbers, where x is a command line parameter to my program. At the current moment, I believe my program is entering an infinite loop, but I'm not sure why it is occurring. I believe I am executing the semaphores correctly. You compile it like this: gcc -o prodcon prodcon.cpp -lpthread -lrt Then to run, ./prodcon 100(the number of randum nums to produce) This is my code. typedef int buffer_item; #include <stdlib.h> #include <stdio.h> #include <pthread.h> #include <semaphore.h> #include <unistd.h> #define BUFF_SIZE 10 #define RAND_DIVISOR 100000000 #define TRUE 1 //two threads void *Producer(void *param); void *Consumer(void *param); int insert_item(buffer_item item); int remove_item(buffer_item *item); int returnRandom(); //the global semaphores sem_t empty, full, mutex; //the buffer buffer_item buf[BUFF_SIZE]; //buffer counter int counter; //number of random numbers to produce int numRand; int main(int argc, char** argv) { /* thread ids and attributes */ pthread_t pid, cid; pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM); numRand = atoi(argv[1]); sem_init(&empty,0,BUFF_SIZE); sem_init(&full,0,0); sem_init(&mutex,0,0); printf("main started\n"); pthread_create(&pid, &attr, Producer, NULL); pthread_create(&cid, &attr, Consumer, NULL); printf("main gets here"); pthread_join(pid, NULL); pthread_join(cid, NULL); printf("main done\n"); return 0; } //generates a randum number between 1 and 100 int returnRandom() { int num; srand(time(NULL)); num = rand() % 100 + 1; return num; } //begin producing items void *Producer(void *param) { buffer_item item; int i; for(i = 0; i < numRand; i++) { //sleep for a random period of time int rNum = rand() / RAND_DIVISOR; sleep(rNum); //generate a random number item = returnRandom(); //acquire the empty lock sem_wait(&empty); //acquire the mutex lock sem_wait(&mutex); if(insert_item(item)) { fprintf(stderr, " Producer report error condition\n"); } else { printf("producer produced %d\n", item); } /* release the mutex lock */ sem_post(&mutex); /* signal full */ sem_post(&full); } return NULL; } /* Consumer Thread */ void *Consumer(void *param) { buffer_item item; int i; for(i = 0; i < numRand; i++) { /* sleep for a random period of time */ int rNum = rand() / RAND_DIVISOR; sleep(rNum); /* aquire the full lock */ sem_wait(&full); /* aquire the mutex lock */ sem_wait(&mutex); if(remove_item(&item)) { fprintf(stderr, "Consumer report error condition\n"); } else { printf("consumer consumed %d\n", item); } /* release the mutex lock */ sem_post(&mutex); /* signal empty */ sem_post(&empty); } return NULL; } /* Add an item to the buffer */ int insert_item(buffer_item item) { /* When the buffer is not full add the item and increment the counter*/ if(counter < BUFF_SIZE) { buf[counter] = item; counter++; return 0; } else { /* Error the buffer is full */ return -1; } } /* Remove an item from the buffer */ int remove_item(buffer_item *item) { /* When the buffer is not empty remove the item and decrement the counter */ if(counter > 0) { *item = buf[(counter-1)]; counter--; return 0; } else { /* Error buffer empty */ return -1; } }

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• Application is crash..

  - by user338322

  Below is my crash Report. 0 0x326712f8 in prepareForMethodLookup () 1 0x3266cf5c in lookUpMethod () 2 0x32668f28 in objc_msgSend_uncached () 3 0x33f70996 in NSPopAutoreleasePool () 4 0x33f82a6c in -[NSAutoreleasePool drain] () 5 0x00003d3e in -[CameraViewcontroller save:] (self=0x811400, _cmd=0x319c00d4, number=0x11e210) at /Users/hardikrathore/Desktop/LiveVideoRecording/Classes/CameraViewcontroller.m:266 6 0x33f36f8a in __NSFireDelayedPerform () 7 0x32da44c2 in CFRunLoopRunSpecific () 8 0x32da3c1e in CFRunLoopRunInMode () 9 0x31bb9374 in GSEventRunModal () 10 0x30bf3c30 in -[UIApplication _run] () 11 0x30bf2230 in UIApplicationMain () 12 0x00002650 in main (argc=1, argv=0x2ffff474) at /Users/hardikrathore/Desktop/LiveVideoRecording/main.m:14 And this is the code. lines, where I am getting the error. -(void)save:(id)number { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; j =[number intValue]; while(screens[j] != NULL){ NSLog(@" image made : %d",j); UIImage * image = [UIImage imageWithCGImage:screens[j]]; image=[self imageByCropping:image toRect:CGRectMake(0, 0, 320, 240)]; NSData *imgdata = UIImageJPEGRepresentation(image,0.3); [image release]; CGImageRelease(screens[j]); screens[j] = NULL; UIImage * image1 = [UIImage imageWithCGImage:screens[j+1]]; image1=[self imageByCropping:image1 toRect:CGRectMake(0, 0, 320, 240)]; NSData *imgdata1 = UIImageJPEGRepresentation(image1,0.3); [image1 release]; CGImageRelease(screens[j+1]); screens[j+1] = NULL; NSString *urlString=@"http://www.test.itmate4.com/iPhoneToServerTwice.php"; // setting up the request object now NSMutableURLRequest *request = [[NSMutableURLRequest alloc]init]; [request setURL:[NSURL URLWithString:urlString]]; [request setHTTPMethod:@"POST"]; NSString *fileName=[VideoID stringByAppendingString:@"_"]; fileName=[fileName stringByAppendingString:[NSString stringWithFormat:@"%d",k]]; NSString *fileName2=[VideoID stringByAppendingString:@"_"]; fileName2=[fileName2 stringByAppendingString:[NSString stringWithFormat:@"%d",k+1]]; /* add some header info now we always need a boundary when we post a file also we need to set the content type You might want to generate a random boundary.. this is just the same as my output from wireshark on a valid html post */ NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"]; NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary]; [request addValue:contentType forHTTPHeaderField: @"Content-Type"]; /* now lets create the body of the post */ //NSString *count=[NSString stringWithFormat:@"%d",front];; NSMutableData *body = [NSMutableData data]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; //[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; count=\"@\"";filename=\"%@.jpg\"\r\n",count,fileName] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"%@.jpg\"\r\n",fileName] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[NSData dataWithData:imgdata]]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; //second boundary NSString *string1 = [[NSString alloc] initWithFormat:@"\r\n--%@\r\n",boundary]; NSString *string2 =[[NSString alloc] initWithFormat:@"Content-Disposition: form-data; name=\"userfile2\"; filename=\"%@.jpg\"\r\n",fileName2]; NSString *string3 =[[NSString alloc] initWithFormat:@"\r\n--%@--\r\n",boundary]; [body appendData:[string1 dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[string2 dataUsingEncoding:NSUTF8StringEncoding]]; //experiment //[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile2\"; filename=\"%@.jpg\"\r\n",fileName2] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[NSData dataWithData:imgdata1]]; //[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[string3 dataUsingEncoding:NSUTF8StringEncoding]]; // setting the body of the post to the reqeust [request setHTTPBody:body]; // now lets make the connection to the web NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]; NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding]; if([returnString isEqualToString:@"SUCCESS"]) { NSLog(returnString); k=k+2; j=j+2; [self performSelectorInBackground:@selector(save:) withObject:(id)[NSNumber numberWithInt:j]]; } //k=k+2; [imgdata release]; [imgdata1 release]; [NSThread sleepForTimeInterval:.01]; } [pool drain]; <-------------Line 266 } As you can see in log report. I am getting the error, Line 266. Some autorelease problem Any help !!!? coz I am not getting why its happening.

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• EXC_BAD_ACCESS at UITableView on IOS

  - by Suprie

  Hi all, When scrolling through table, my application crash and console said it was EXC_BAD_ACCESS. I've look everywhere, and people suggest me to use NSZombieEnabled on my executables environment variables. I've set NSZombieEnabled, NSDebugEnabled, MallocStackLogging and MallocStackLoggingNoCompact to YES on my executables. But apparently i still can't figure out which part of my program that cause EXC_BAD_ACCESS. This is what my console said [Session started at 2010-12-21 21:11:21 +0700.] GNU gdb 6.3.50-20050815 (Apple version gdb-1510) (Wed Sep 22 02:45:02 UTC 2010) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 9335. TwitterSearch(9335) malloc: recording malloc stacks to disk using standard recorder TwitterSearch(9335) malloc: process 9300 no longer exists, stack logs deleted from /tmp/stack-logs.9300.TwitterSearch.suirlR.index TwitterSearch(9335) malloc: stack logs being written into /tmp/stack- logs.9335.TwitterSearch.tQJAXk.index 2010-12-21 21:11:25.446 TwitterSearch[9335:207] View Did Load Program received signal: “EXC_BAD_ACCESS”. And this is when i tried to type backtrace on gdb : Program received signal: “EXC_BAD_ACCESS”. (gdb) backtrace #0 0x00f20a67 in objc_msgSend () #1 0x0565cd80 in ?? () #2 0x0033b7fa in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] () #3 0x0033177f in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] () #4 0x00346450 in -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] () #5 0x0033e538 in -[UITableView layoutSubviews] () #6 0x01ffc451 in -[CALayer layoutSublayers] () #7 0x01ffc17c in CALayerLayoutIfNeeded () #8 0x01ff537c in CA::Context::commit_transaction () #9 0x01ff50d0 in CA::Transaction::commit () #10 0x020257d5 in CA::Transaction::observer_callback () #11 0x00d9ffbb in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ () #12 0x00d350e7 in __CFRunLoopDoObservers () #13 0x00cfdbd7 in __CFRunLoopRun () #14 0x00cfd240 in CFRunLoopRunSpecific () #15 0x00cfd161 in CFRunLoopRunInMode () #16 0x01a73268 in GSEventRunModal () #17 0x01a7332d in GSEventRun () #18 0x002d642e in UIApplicationMain () #19 0x00001d4e in main (argc=1, argv=0xbfffee34) at /Users/suprie/Documents/Projects/Self/cocoa/TwitterSearch/main.m:14 I really appreciate for any clue to help me debug my application. EDIT this is the Header file of table #import <UIKit/UIKit.h> @interface TwitterTableViewController : UITableViewController { NSMutableArray *twitters; } @property(nonatomic,retain) NSMutableArray *twitters; @end and the implementation file #import "TwitterTableViewController.h" @implementation TwitterTableViewController @synthesize twitters; #pragma mark - #pragma mark Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { // Return the number of sections. return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in the section. return [twitters count]; } - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { return 90.0f; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { const NSInteger TAG_IMAGE_VIEW = 1001; const NSInteger TAG_TWEET_VIEW = 1002; const NSInteger TAG_FROM_VIEW = 1003; static NSString *CellIdentifier = @"Cell"; UIImageView *imageView; UILabel *tweet; UILabel *from; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; // Image imageView = [[[[UIImageView alloc] initWithFrame:CGRectMake(5.0f, 5.0f, 60.0f, 60.0f)] autorelease] retain]; [cell.contentView addSubview:imageView]; imageView.tag = TAG_IMAGE_VIEW; // Tweet tweet = [[[UILabel alloc] initWithFrame:CGRectMake(105.0f, 5.0f, 200.0f, 50.0f)] autorelease]; [cell.contentView addSubview:tweet]; tweet.tag = TAG_TWEET_VIEW; tweet.numberOfLines = 2; tweet.font = [UIFont fontWithName:@"Helvetica" size:12]; tweet.textColor = [UIColor blackColor]; tweet.backgroundColor = [UIColor clearColor]; // From from = [[[UILabel alloc] initWithFrame:CGRectMake(105.0f, 55.0, 200.0f, 35.0f)] autorelease]; [cell.contentView addSubview:from]; from.tag = TAG_FROM_VIEW; from.numberOfLines = 1; from.font = [UIFont fontWithName:@"Helvetica" size:10]; from.textColor = [UIColor blackColor]; from.backgroundColor = [UIColor clearColor]; } // Configure the cell... NSMutableDictionary *twitter = [twitters objectAtIndex:(NSInteger) indexPath.row]; // cell.text = [twitter objectForKey:@"text"]; tweet.text = (NSString *) [twitter objectForKey:@"text"]; tweet.hidden = NO; from.text = (NSString *) [twitter objectForKey:@"from_user"]; from.hidden = NO; NSString *avatar_url = (NSString *)[twitter objectForKey:@"profile_image_url"]; NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: avatar_url]]; imageView.image = [UIImage imageWithData: imageData]; imageView.hidden = NO; return cell; } #pragma mark - #pragma mark Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSMutableDictionary *twitter = [twitters objectAtIndex:(NSInteger)indexPath.row]; NSLog(@"Twit ini kepilih :%@", [twitter objectForKey:@"text"]); } #pragma mark - #pragma mark Memory management - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; } - (void)viewDidUnload { } - (void)dealloc { [super dealloc]; } @end

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• Custom Memory Allocator for STL map

  - by Prasoon Tiwari

  This question is about construction of instances of custom allocator during insertion into a std::map. Here is a custom allocator for std::map<int,int> along with a small program that uses it: #include <stddef.h> #include <stdio.h> #include <map> #include <typeinfo> class MyPool { public: void * GetNext() { return malloc(24); } void Free(void *ptr) { free(ptr); } }; template<typename T> class MyPoolAlloc { public: static MyPool *pMyPool; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef T* pointer; typedef const T* const_pointer; typedef T& reference; typedef const T& const_reference; typedef T value_type; template<typename X> struct rebind { typedef MyPoolAlloc<X> other; }; MyPoolAlloc() throw() { printf("-------Alloc--CONSTRUCTOR--------%08x %32s\n", this, typeid(T).name()); } MyPoolAlloc(const MyPoolAlloc&) throw() { printf(" Copy Constructor ---------------%08x %32s\n", this, typeid(T).name()); } template<typename X> MyPoolAlloc(const MyPoolAlloc<X>&) throw() { printf(" Construct T Alloc from X Alloc--%08x %32s %32s\n", this, typeid(T).name(), typeid(X).name()); } ~MyPoolAlloc() throw() { printf(" Destructor ---------------------%08x %32s\n", this, typeid(T).name()); }; pointer address(reference __x) const { return &__x; } const_pointer address(const_reference __x) const { return &__x; } pointer allocate(size_type __n, const void * hint = 0) { if (__n != 1) perror("MyPoolAlloc::allocate: __n is not 1.\n"); if (NULL == pMyPool) { pMyPool = new MyPool(); printf("======>Creating a new pool object.\n"); } return reinterpret_cast<T*>(pMyPool->GetNext()); } //__p is not permitted to be a null pointer void deallocate(pointer __p, size_type __n) { pMyPool->Free(reinterpret_cast<void *>(__p)); } size_type max_size() const throw() { return size_t(-1) / sizeof(T); } void construct(pointer __p, const T& __val) { printf("+++++++ %08x %s.\n", __p, typeid(T).name()); ::new(__p) T(__val); } void destroy(pointer __p) { printf("-+-+-+- %08x.\n", __p); __p->~T(); } }; template<typename T> inline bool operator==(const MyPoolAlloc<T>&, const MyPoolAlloc<T>&) { return true; } template<typename T> inline bool operator!=(const MyPoolAlloc<T>&, const MyPoolAlloc<T>&) { return false; } template<typename T> MyPool* MyPoolAlloc<T>::pMyPool = NULL; int main(int argc, char *argv[]) { std::map<int, int, std::less<int>, MyPoolAlloc<std::pair<const int,int> > > m; //random insertions in the map m.insert(std::pair<int,int>(1,2)); m[5] = 7; m[8] = 11; printf("======>End of map insertions.\n"); return 0; } Here is the output of this program: -------Alloc--CONSTRUCTOR--------bffcdaa6 St4pairIKiiE Construct T Alloc from X Alloc--bffcda77 St13_Rb_tree_nodeISt4pairIKiiEE St4pairIKiiE Copy Constructor ---------------bffcdad8 St13_Rb_tree_nodeISt4pairIKiiEE Destructor ---------------------bffcda77 St13_Rb_tree_nodeISt4pairIKiiEE Destructor ---------------------bffcdaa6 St4pairIKiiE ======Creating a new pool object. Construct T Alloc from X Alloc--bffcd9df St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d028 St4pairIKiiE. Destructor ---------------------bffcd9df St4pairIKiiE Construct T Alloc from X Alloc--bffcd95f St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d048 St4pairIKiiE. Destructor ---------------------bffcd95f St4pairIKiiE Construct T Alloc from X Alloc--bffcd95f St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d068 St4pairIKiiE. Destructor ---------------------bffcd95f St4pairIKiiE ======End of map insertions. Construct T Alloc from X Alloc--bffcda23 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d068. Destructor ---------------------bffcda23 St4pairIKiiE Construct T Alloc from X Alloc--bffcda43 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d048. Destructor ---------------------bffcda43 St4pairIKiiE Construct T Alloc from X Alloc--bffcda43 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d028. Destructor ---------------------bffcda43 St4pairIKiiE Destructor ---------------------bffcdad8 St13_Rb_tree_nodeISt4pairIKiiEE Last two columns of the output show that an allocator for std::pair<const int, int> is constructed everytime there is a insertion into the map. Why is this necessary? Is there a way to suppress this? Thanks! Edit: This code tested on x86 machine with g++ version 4.1.2. If you wish to run it on a 64-bit machine, you'll have to change at least the line return malloc(24). Changing to return malloc(48) should work.

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• Dynamically register constructor methods in an AbstractFactory at compile time using C++ templates

  - by Horacio

  When implementing a MessageFactory class to instatiate Message objects I used something like: class MessageFactory { public: static Message *create(int type) { switch(type) { case PING_MSG: return new PingMessage(); case PONG_MSG: return new PongMessage(); .... } } This works ok but every time I add a new message I have to add a new XXX_MSG and modify the switch statement. After some research I found a way to dynamically update the MessageFactory at compile time so I can add as many messages as I want without need to modify the MessageFactory itself. This allows for cleaner and easier to maintain code as I do not need to modify three different places to add/remove message classes: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <inttypes.h> class Message { protected: inline Message() {}; public: inline virtual ~Message() { } inline int getMessageType() const { return m_type; } virtual void say() = 0; protected: uint16_t m_type; }; template<int TYPE, typename IMPL> class MessageTmpl: public Message { enum { _MESSAGE_ID = TYPE }; public: static Message* Create() { return new IMPL(); } static const uint16_t MESSAGE_ID; // for registration protected: MessageTmpl() { m_type = MESSAGE_ID; } //use parameter to instanciate template }; typedef Message* (*t_pfFactory)(); class MessageFactory· { public: static uint16_t Register(uint16_t msgid, t_pfFactory factoryMethod) { printf("Registering constructor for msg id %d\n", msgid); m_List[msgid] = factoryMethod; return msgid; } static Message *Create(uint16_t msgid) { return m_List[msgid](); } static t_pfFactory m_List[65536]; }; template <int TYPE, typename IMPL> const uint16_t MessageTmpl<TYPE, IMPL >::MESSAGE_ID = MessageFactory::Register( MessageTmpl<TYPE, IMPL >::_MESSAGE_ID, &MessageTmpl<TYPE, IMPL >::Create); class PingMessage: public MessageTmpl < 10, PingMessage > {· public: PingMessage() {} virtual void say() { printf("Ping\n"); } }; class PongMessage: public MessageTmpl < 11, PongMessage > {· public: PongMessage() {} virtual void say() { printf("Pong\n"); } }; t_pfFactory MessageFactory::m_List[65536]; int main(int argc, char **argv) { Message *msg1; Message *msg2; msg1 = MessageFactory::Create(10); msg1->say(); msg2 = MessageFactory::Create(11); msg2->say(); delete msg1; delete msg2; return 0; } The template here does the magic by registering into the MessageFactory class, all new Message classes (e.g. PingMessage and PongMessage) that subclass from MessageTmpl. This works great and simplifies code maintenance but I still have some questions about this technique: Is this a known technique/pattern? what is the name? I want to search more info about it. I want to make the array for storing new constructors MessageFactory::m_List[65536] a std::map but doing so causes the program to segfault even before reaching main(). Creating an array of 65536 elements is overkill but I have not found a way to make this a dynamic container. For all message classes that are subclasses of MessageTmpl I have to implement the constructor. If not it won't register in the MessageFactory. For example commenting the constructor of the PongMessage: class PongMessage: public MessageTmpl < 11, PongMessage > { public: //PongMessage() {} /* HERE */ virtual void say() { printf("Pong\n"); } }; would result in the PongMessage class not being registered by the MessageFactory and the program would segfault in the MessageFactory::Create(11) line. The question is why the class won't register? Having to add the empty implementation of the 100+ messages I need feels inefficient and unnecessary.

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• Undefined reference to ...

  - by Patrick LaChance

  I keep getting this error message every time I try to compile, and I cannot find out what the problem is. any help would be greatly appreciated: C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::List()' C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::add(int)' collect2: ld returned 1 exit status code: //List.h #ifndef LIST_H #define LIST_H #include <exception> //brief Definition of linked list class class List { public: /** \brief Exception for operating on empty list */ class Empty : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Exception for invalid operations other than operating on an empty list */ class InvalidOperation : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Node within List */ class Node { public: /** data element stored in this node */ int element; /** next node in list */ Node* next; /** previous node in list */ Node* previous; Node (int element); ~Node(); void print() const; void printDebug() const; }; List(); ~List(); void add(int element); void remove(int element); int first()const; int last()const; int removeFirst(); int removeLast(); bool isEmpty()const; int size()const; void printForward() const; void printReverse() const; void printDebug() const; /** enables extra output for debugging purposes */ static bool traceOn; private: /** head of list */ Node* head; /** tail of list */ Node* tail; /** count of number of nodes */ int count; }; #endif //List.cpp I only included the parts of List.cpp that might be the issue #include "List.h" #include <iostream> #include <iomanip> using namespace std; List::List() { //List::size = NULL; head = NULL; tail = NULL; } List::~List() { Node* current; while(head != NULL) { current = head-> next; delete current->previous; if (current->next!=NULL) { head = current; } else { delete current; } } } void List::add(int element) { Node* newNode; Node* current; newNode->element = element; if(newNode->element > head->element) { current = head->next; } else { head->previous = newNode; newNode->next = head; newNode->previous = NULL; return; } while(newNode->element > current->element) { current = current->next; } if(newNode->element <= current->element) { newNode->previous = current->previous; newNode->next = current; } } //main.cpp #include "List.h" #include <iostream> #include <string> using namespace std; //void add(int element); int main (char** argv, int argc) { List* MyList = new List(); bool quit = false; string value; int element; while(quit==false) { cin>>value; if(value == "add") { cin>>element; MyList->add(element); } if(value=="quit") { quit = true; } } return 0; } I'm doing everything I think I'm suppose to be doing. main.cpp isn't complete yet, just trying to get the add function to work first. Any help will be greatly appreciated.

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• libcurl - unable to download a file

  - by marmistrz

  I'm working on a program which will download lyrics from sites like AZLyrics. I'm using libcurl. It's my code lyricsDownloader.cpp #include "lyricsDownloader.h" #include <curl/curl.h> #include <cstring> #include <iostream> #define DEBUG 1 ///////////////////////////////////////////////////////////////////////////// size_t lyricsDownloader::write_data_to_var(char *ptr, size_t size, size_t nmemb, void *userdata) // this function is a static member function { ostringstream * stream = (ostringstream*) userdata; size_t count = size * nmemb; stream->write(ptr, count); return count; } string AZLyricsDownloader::toProviderCode() const { /*this creates an url*/ } CURLcode AZLyricsDownloader::download() { CURL * handle; CURLcode err; ostringstream buff; handle = curl_easy_init(); if (! handle) return static_cast<CURLcode>(-1); // set verbose if debug on curl_easy_setopt( handle, CURLOPT_VERBOSE, DEBUG ); curl_easy_setopt( handle, CURLOPT_URL, toProviderCode().c_str() ); // set the download url to the generated one curl_easy_setopt(handle, CURLOPT_WRITEDATA, &buff); curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, &AZLyricsDownloader::write_data_to_var); err = curl_easy_perform(handle); // The segfault should be somewhere here - after calling the function but before it ends cerr << "cleanup\n"; curl_easy_cleanup(handle); // copy the contents to text variable lyrics = buff.str(); return err; } main.cpp #include <QString> #include <QTextEdit> #include <iostream> #include "lyricsDownloader.h" int main(int argc, char *argv[]) { AZLyricsDownloader dl(argv[1], argv[2]); dl.perform(); QTextEdit qtexted(QString::fromStdString(dl.lyrics)); cout << qPrintable(qtexted.toPlainText()); return 0; } When running ./maelyrica Anthrax Madhouse I'm getting this logged from curl * About to connect() to azlyrics.com port 80 (#0) * Trying 174.142.163.250... * connected * Connected to azlyrics.com (174.142.163.250) port 80 (#0) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: azlyrics.com Accept: */* < HTTP/1.1 301 Moved Permanently < Server: nginx/1.0.12 < Date: Thu, 05 Jul 2012 16:59:21 GMT < Content-Type: text/html < Content-Length: 185 < Connection: keep-alive < Location: http://www.azlyrics.com/lyrics/anthrax/madhouse.html < Segmentation fault Strangely, the file is there. The same error is displayed when there's no such page (redirect to azlyrics.com mainpage) What am I doing wrong? Thanks in advance EDIT: I made the function for writing data static, but this changes nothing. Even wget seems to have problems $ wget http://www.azlyrics.com/lyrics/anthrax/madhouse.html --2012-07-06 10:36:05-- http://www.azlyrics.com/lyrics/anthrax/madhouse.html Resolving www.azlyrics.com... 174.142.163.250 Connecting to www.azlyrics.com|174.142.163.250|:80... connected. HTTP request sent, awaiting response... No data received. Retrying. Why does opening the page in a browser work and wget/curl not? EDIT2: After adding this: curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1); The log is: * About to connect() to azlyrics.com port 80 (#0) * Trying 174.142.163.250... * connected * Connected to azlyrics.com (174.142.163.250) port 80 (#0) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: azlyrics.com Accept: */* < HTTP/1.1 301 Moved Permanently < Server: nginx/1.0.12 < Date: Fri, 06 Jul 2012 09:09:47 GMT < Content-Type: text/html < Content-Length: 185 < Connection: keep-alive < Location: http://www.azlyrics.com/lyrics/anthrax/madhouse.html < * Ignoring the response-body * Connection #0 to host azlyrics.com left intact * Issue another request to this URL: 'http://www.azlyrics.com/lyrics/anthrax/madhouse.html' * About to connect() to www.azlyrics.com port 80 (#1) * Trying 174.142.163.250... * connected * Connected to www.azlyrics.com (174.142.163.250) port 80 (#1) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: www.azlyrics.com Accept: */* < HTTP/1.1 200 OK < Server: nginx/1.0.12 < Date: Fri, 06 Jul 2012 09:09:47 GMT < Content-Type: text/html < Transfer-Encoding: chunked < Connection: keep-alive < Segmentation fault

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• C++ converting binary(P5) image to ascii(P2) image (.pgm)

  - by tubby

  I am writing a simple program to convert grayscale binary (P5) to grayscale ascii (P2) but am having trouble reading in the binary and converting it to int. #include <iostream> #include <fstream> #include <sstream> using namespace::std; int usage(char* arg) { // exit program cout << arg << ": Error" << endl; return -1; } int main(int argc, char* argv[]) { int rows, cols, size, greylevels; string filetype; // open stream in binary mode ifstream istr(argv[1], ios::in | ios::binary); if(istr.fail()) return usage(argv[1]); // parse header istr >> filetype >> rows >> cols >> greylevels; size = rows * cols; // check data cout << "filetype: " << filetype << endl; cout << "rows: " << rows << endl; cout << "cols: " << cols << endl; cout << "greylevels: " << greylevels << endl; cout << "size: " << size << endl; // parse data values int* data = new int[size]; int fail_tracker = 0; // find which pixel failing on for(int* ptr = data; ptr < data+size; ptr++) { char t_ch; // read in binary char istr.read(&t_ch, sizeof(char)); // convert to integer int t_data = static_cast<int>(t_ch); // check if legal pixel if(t_data < 0 || t_data > greylevels) { cout << "Failed on pixel: " << fail_tracker << endl; cout << "Pixel value: " << t_data << endl; return usage(argv[1]); } // if passes add value to data array *ptr = t_data; fail_tracker++; } // close the stream istr.close(); // write a new P2 binary ascii image ofstream ostr("greyscale_ascii_version.pgm"); // write header ostr << "P2 " << rows << cols << greylevels << endl; // write data int line_ctr = 0; for(int* ptr = data; ptr < data+size; ptr++) { // print pixel value ostr << *ptr << " "; // endl every ~20 pixels for some readability if(++line_ctr % 20 == 0) ostr << endl; } ostr.close(); // clean up delete [] data; return 0; } sample image - Pulled this from an old post. Removed the comment within the image file as I am not worried about this functionality now. When compiled with g++ I get output: $> ./a.out a.pgm filetype: P5 rows: 1024 cols: 768 greylevels: 255 size: 786432 Failed on pixel: 1 Pixel value: -110 a.pgm: Error The image is a little duck and there's no way the pixel value can be -110...where am I going wrong? Thanks.

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