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  • How to return a string literal from a function

    - by skydoor
    Hi I am always confused about return a string literal or a string from a function. I was told that there might be memory leak because you don't know when the memory will be deleted? For example, in the code below, how to implement foo() so that make the output of the code is "Hello World"? void foo ( ) // you can add parameters here. { } int main () { char *c; foo ( ); printf ("%s",c); return 0; } Also if the return type of foo() is not void, but you can return char*, what should it be.

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  • Why does accessing a member of a malloced array of structs seg fault?

    - by WSkinner
    I am working through Learn C The Hard Way and am stumped on something. I've written a simplified version of the problem I am running into to make it easier to get down to it. Here is the code: #include <stdlib.h> #define GROUP_SIZE 10 #define DATA_SIZE 64 struct Dummy { char *name; }; struct Group { struct Dummy **dummies; }; int main() { struct Group *group1 = malloc(sizeof(struct Group)); group1->dummies = malloc(sizeof(struct Dummy) * GROUP_SIZE); struct Dummy *dummy1 = group1->dummies[3]; // Why does this seg fault? dummy1->name = (char *) malloc(DATA_SIZE); return 0; } when I try to set the name pointer on one of my dummies I get a seg fault. Using valgrind it tells me this is uninitialized space. Why is this?

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • Sorting array of structs

    - by mrblippy
    Hi, i am having trouble making a method to sort an array of structs. i am tring to sort them in ascending order based on classcode. any help you could give would be appreciated struct unit { char classcode[4]; char *classname; }; void insertion_sort(struct unit u[], int n) { int j, p; struct unit tmp[1]; for(p = 1; p < n; p++) { tmp[0] = u[p]; for(j = p; j > 0 && (strcmp(tmp[j-1].classcode, tmp[p].classcode) > 0); j--) u[j] = u[j-1]; u[j] = tmp[0]; } }

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  • C++ catch constructor exception

    - by aaa
    hi. I do not seem to understand how to catch constructor exception. Here is relevant code: struct Thread { rysq::cuda::Fock fock_; template<class iterator> Thread(const rysq::cuda::Centers &centers, const iterator (&blocks)[4]) : fock_() { if (!fock_) throw; } }; Thread *ct; try { ct = new Thread(centers_, blocks); } catch(...) { return false; } // catch never happens, So catch statement do not execute and I get unhandled exception. What did I do wrong? this is straight C++ using g++.

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  • newline character on text area

    - by Prady
    I have a custom field called Current_Address__c which is of datatype textarea. I need to populate this field in the format below. ie a newline char after street and another newline after zip. street City state Zip Country The values of city state zip country etc are been taken from contact object. I dont want to use this as a formula field. So i need to populate it in my controller and display it on my VF page. I am trying to add a newline char by using the code below this.customobj.Current_Address__c = currentStreet + '\\n ' + currentCity + ' ' + currentState + ' ' + currentZIP + '\\n ' + currentCountry ; i had also used \n instead of \n. It still show the field in one line instead of 3 lines

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  • Redirecting one file to another using dub2 and strtok

    - by Sergiy Zakharov
    OK, here goes. I have to write a program, in which I need to use strtok and dup2 to redirect one file to another, but I need to also have the user to actually put the command cat < file1 file2, but not from the shell, but instead by using my program. That's why I need strtok. And the reason my program doesn't work is probably because of that, because I don't really understand how strtok works. I found a similar program on the internet, but they just take the ls command and redirect it to the file. That's it. My program is much more complicated. I mean, it would've been easier just to say in shell cat < file1 file2, but for some reason they want us to do it this way. So, anyways, here is what I have so far (here I just combined what I have found on the internet with what I already had from before. We had to do something similar but then the user would just go ls or ls -l. Very simple stuff. This is much harder, for me, at least.) #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <errno.h> #include <sys/wait.h> #include <string.h> int main() { pid_t pid; char line[256]; char *args[129]; int i; int fd; int status; char *temp; while (1) { printf(">"); if (fgets(line, 256, stdin) == 0) { exit(0); } else { pid = fork(); if (pid == 0) { i = 0; temp = strtok("<",line); while (temp != NULL) { args[i++] = temp; temp = strtok(">",line); args[i] = '\0'; } fd = open("hello", O_RDONLY); dup2(fd, STDIN_FILENO); fd = open("world", O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU); dup2(fd, STDOUT_FILENO ); close(fd); execvp(args[0], args); } else { close(fd); wait(&status); } } } } Any help would be greatly appreciated.

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  • test cases for testing a strtok-alike function [C++]

    - by Neeraj
    Consider the following class definition: class StrToTokens { StrToTokens(const char* str, const char* delimiters = "\t\r\n"); //constructor string getNextToken(); void reset(); bool empty(); } Can someone list some good testcases to test the above class. A few I could think of are: empty string, empty delimiters, repeated delimiters, consecutive delimiters, string with only delimiters. However, the interviewer expected some more(better ones). Can you help out. Thanks.

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  • setsockopt (sys/socket.h)

    - by lojin
    The prototype for setsockopt is: int setsockopt(int socket, int level, int option_name, const void *option_value, socklen_t option_len); Are the following all correct ? Which are not ? a.) int buffsize = 50000; setsockopt(s, SOL_SOCKET, SO_RCVBUF, (char *)&buffsize, sizeof(buffsize)); b.) int buffsize = 50000; setsockopt(s, SOL_SOCKET, SO_RCVBUF, (void *)&buffsize, sizeof(buffsize)); c.) char *buffsize = "50000"; setsockopt(s, SOL_SOCKET, SO_RCVBUF, buffsize, strlen(buffsize)); d.) setsockopt(s, SOL_SOCKET, SO_RCVBUF, "50000", 5);

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  • Haskell. Numbers in binary numbers. words

    - by Katja
    Hi! I need to code words into binary numbers. IN: "BCD..." OUT:1011... I have written already funktion for coding characters into siple numbers IN: 'C' OUT: 3 IN: 'c' OUT: 3 lett2num :: Char -> Int lett2num x | (ord 'A' <= ord x) && (ord x <= ord 'Z') = (ord x - ord 'A') + 1 | (ord 'a' <= ord x) && (ord x <= ord 'z') = (ord x - ord 'a') +1 num2lett :: Int -> Char num2lett n | (n <= ord 'A') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) | (n <= ord 'a') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) I wrote as well function for codind simple numbers into binary. num2bin :: Int->[Int] num2bin 0 = [] num2bin n | n>=0 = n `mod` 2 : (num2bin( n `div` 2)) | otherwise = error but I donw want those binary numbers to be in a list how can I get rid of the lists? Thanks

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  • PLEASE HELP JAVA/SQL question

    - by fred-ghosn
    Hello everyone, well I'm new here and I really need some help.. I want to create a table and this table's name will be inserted from a textfield. However when I run the query it's giving me an error, any help on this one? Ill paste the code here: public boolean CreateTable() { TableNumber=jTextField4.getText(); try { String password = null; String s = "CREATE TABLE '"+TableNumber+'" (Item char(50),Price char(50))"; ConnectionForOrders(); stmt = conn.createStatement(); stmt.executeUpdate(s); boolean f=false; ConnectionForOrdersclose();

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  • C++ : size of int, long, etc...

    - by Jérôme
    I'm looking for detailed informations regarding the size of basic C++ types. I know that it depends on the architecture (16 bits, 32 bits, 64 bits) and the compiler. But are there any standards ? I'm using Visual Studio 2008 on a 32 bit achitecture. Here is what I get : char : 1 byte short : 2 bytes int : 4 bytes long : 4 bytes float : 4 bytes double : 8 bytes I tried to find, without much success, reliable informations telling the sizes of char, short, int , long, double, float (and other types I don't think of) under different architecture and compiler.

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  • Hiredis waiting for message

    - by Vivek Goel
    I am using hiredis C library to connect to redis server. I am not able to figure out how to wait for new messages after subscribing to new message. My code look like: signal(SIGPIPE, SIG_IGN ); struct event_base *base = event_base_new(); redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379); if (c->err) { /* Let *c leak for now... */ printf("Error: %s\n", c->errstr); return 1; } redisLibeventAttach(c, base); redisAsyncSetConnectCallback(c, connectCallback); redisAsyncSetDisconnectCallback(c, disconnectCallback); redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1], strlen(argv[argc - 1])); redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key"); redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo"); Now how to tell hiredis to wait for message on channel ?

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  • How to move the mouse

    - by GroundZero
    I'm making a little bot in C#. At the moment it works pretty well, it can load text from a file and type it for you. But for now, I need to manualy click the textfield to put the focus on it, remaximize my form and then click the Type-button. After the typing, I need to manualy slide the scorebar and press submit. I'd like to know how I can move my mouse with C# and if possible, if possible I'd like to load the mouse positions from a xml-file. I need to move to the textfield, click in it to focus on it, start the type script, move to the slider, hold the mouse down on it while dragging, releasing it on the correct position & clicking on the submitbutton This is what I have for now: To load in the variables, I'm using this script: private void Initialize() { XmlTextReader reader = new XmlTextReader(Application.StartupPath + @"..\..\..\CursorPositions.xml"); while (reader.Read()) { switch (reader.NodeType) { case XmlNodeType.Element: // The node is an element. element = reader.Value; break; case XmlNodeType.Text: //Display the text in each element. switch (element) { case "Textbox-X": textX = int.Parse(reader.Value); break; case "Textbox-Y": textY = int.Parse(reader.Value); break; case "SliderBegin-X": sliderX = int.Parse(reader.Value); break; case "SliderBegin-Y": sliderY = int.Parse(reader.Value); break; case "SubmitButton-X": submitX = int.Parse(reader.Value); break; case "SubmitButton-Y": submitY = int.Parse(reader.Value); break; } break; } } This is the xml-file: <?xml version="1.0" encoding="utf-8" ?> <CursorPositions> <Textbox-X>430</Textbox-X> <Textbox-Y>270</Textbox-Y> <SliderBegin-X>430</SliderBegin-X> <SliderBegin-Y>470</SliderBegin-Y> <SubmitButton-X>860</SubmitButton-X> <SubmitButton-Y>365</SubmitButton-Y> </CursorPositions> To move the mouse I'm using this piece of code: public partial class FrmMain : Form { [System.Runtime.InteropServices.DllImport("user32.dll")] public static extern void mouse_event(int dwFlags, int dx, int dy, int cButtons, int dwExtraInfo); public const int MOUSEEVENTF_LEFTDOWN = 0x0002; public const int MOUSEEVENTF_LEFTUP = 0x0004; public const int MOUSEEVENTF_RIGHTDOWN = 0x0008; public const int MOUSEEVENTF_RIGHTUP = 0x0010; ... private void btnStart_Click(object sender, EventArgs e) { // start button (de)activates loop if (!running) { btnStart.Text = "Stop"; btnStart.Cursor = Cursors.No; running = true; } else { btnStart.Text = "Start"; btnStart.Cursor = Cursors.AppStarting; running = false; } while (running) { // move to textbox & type Cursor.Position = new Point(textX, textY); mouse_event(MOUSEEVENTF_LEFTDOWN, textX, textY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, textX, textY, 0, 0); Type(); // wait 90 seconds till slider available Thread.Sleep(90 * 1000); // move to slider & slide according to score Cursor.Position = new Point(sliderX, sliderY); mouse_event(MOUSEEVENTF_LEFTDOWN, sliderX, sliderY, 0, 0); Cursor.Position = new Point(sliderX + 345 / 10 * score, sliderY); mouse_event(MOUSEEVENTF_LEFTUP, sliderX + 345 / 10 * score, sliderY, 0, 0); // submit Cursor.Position = new Point(submitX, submitY); mouse_event(MOUSEEVENTF_LEFTDOWN, submitX, submitY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, submitX, submitY, 0, 0); // wait 10 sec to be sure it's submitted Thread.Sleep(10 * 1000); // refresh page SendKeys.SendWait("{F5}"); // get new text NewText(); // wait 10 sec to refresh and load song Thread.Sleep(10 * 1000); } } } PS: I get the coordinates via my form. I've got 2 labels that show my X & Y coordinates. To capture them outside the form, I press and hold my Left Mouse Button and 'drag' it outside the form to the correct place. This way I get the coordinates of my mouse outside the form

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  • Are pointers primitive types in C++?

    - by Space_C0wb0y
    I was wondering about the last constructor for std::string mentioned here. It says: template<class InputIterator> string (InputIterator begin, InputIterator end); If InputIterator is an integral type, behaves as the sixth constructor version (the one right above this) by typecasting begin and end to call it: string(static_cast<size_t>(begin),static_cast<char>(end)); In any other case, the parameters are taken as iterators, and the content is initialized with the values of the elements that go from the element referred by iterator begin to the element right before the one referred by iterator end. So what does that mean if InputIterator is a char * ?

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  • How to extract img src, title and alt from html using php?

    - by Sam
    I would like to create a page where all images which reside on my website are listed with title and alternative representation. I already wrote me a little program to find and load all html files, but now I am stuck at how to extract src, title and alt from the html < img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny"/ I guess this should be done with some regex, but since the order of the tags may vary, and I need all of them, I don't really know how to parse this in an elegant way (I could do it the hard char by char way, but thats painful).

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  • error in encryption program

    - by Raja
    #include<iostream> #include<math.h> #include<string> using namespace std; int gcd(int n,int m) { if(m<=n && n%m ==0) return m; if(n<m) return gcd(m,n); else return gcd(m,n%m); } int REncryptText(char m) { int p = 11, q = 3; int e = 3; int n = p * q; int phi = (p - 1) * (q - 1); int check1 = gcd(e, p - 1); int check2 = gcd(e, q - 1); int check3 = gcd(e, phi); // // Compute d such that ed = 1 (mod phi) //i.e. compute d = e-1 mod phi = 3-1 mod 20 //i.e. find a value for d such that phi divides (ed-1) //i.e. find d such that 20 divides 3d-1. //Simple testing (d = 1, 2, ...) gives d = 7 // double d = Math.Pow(e, -1) % phi; int d = 7; // public key = (n,e) // (33,3) //private key = (n,d) //(33 ,7) double g = pow(m,e); int ciphertext = g %n; // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. //double decrypt = Math.Pow(ciphertext, d) % n; return ciphertext; } int main() { char plaintext[80],str[80]; cout<<" enter the text you want to encrpt"; cin.get(plaintext,79); int l =strlen(plaintext); for ( int i =0 ; i<l ; i++) { char s = plaintext[i]; str[i]=REncryptText(s); } for ( int i =0 ; i<l ; i++) { cout<<"the encryption of string"<<endl; cout<<str[i]; } return 0; }

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  • Prolog .. Can i convert from a list of chars to a string or term in Prolog !!

    - by AhmadAssaf
    i use read_line_to_codes(Stream,Line) to read a line from a file .. first is there any way to read a line and assign it to a term in prolog ?? if not i managed to read a line and put it in this char list .. now this char list contains spaces .. which is bad .. so i want to convert it to a term or a string in prolog so that i can process it easier .. spaces cannot be atoms so thats a problem .. i appreciate the help !!

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  • how to reloadData in tableView when tableview access data from database.

    - by Ajeet Kumar Yadav
    I am new in iphone i am developing a application that take value from data base and display data in tableview. in this application we save data from one data table to other data table this is when add first time work and when we do second time application is crash. how to solve this problem i am not understand code is given bellow my appdelegate code for insert value from one table to other is given bellow -(void)sopinglist { //////databaseName= @"SanjeevKapoor.sqlite"; databaseName =@"AjeetTest.sqlite"; NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDir = [documentPaths objectAtIndex:0]; databasePath =[documentsDir stringByAppendingPathComponent:databaseName]; [self checkAndCreateDatabase]; list1 = [[NSMutableArray alloc] init]; sqlite3 *database; if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { if(addStmt == nil) { ///////////const char *sql = "insert into Dataa(item) Values(?)"; const char *sql = " insert into Slist select * from alootikki"; ///////////// const char *sql =" Update Slist ( Incredients, Recipename,foodtype) Values(?,?,?)"; if(sqlite3_prepare_v2(database, sql, -1, &addStmt, NULL) != SQLITE_OK) NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(database)); } /////for( NSString * j in k) sqlite3_bind_text(addStmt, 1, [k UTF8String], -1, SQLITE_TRANSIENT); //sqlite3_bind_int(addStmt,1,i); // sqlite3_bind_text(addStmt, 1, [coffeeName UTF8String], -1, SQLITE_TRANSIENT); // sqlite3_bind_double(addStmt, 2, [price doubleValue]); if(SQLITE_DONE != sqlite3_step(addStmt)) NSAssert1(0, @"Error while inserting data. '%s'", sqlite3_errmsg(database)); else //SQLite provides a method to get the last primary key inserted by using sqlite3_last_insert_rowid coffeeID = sqlite3_last_insert_rowid(database); //Reset the add statement. sqlite3_reset(addStmt); // sqlite3_clear_bindings(detailStmt); //} } sqlite3_finalize(addStmt); addStmt = nil; sqlite3_close(database); } And the table View code for access data from database is given bellow SanjeevKapoorAppDelegate *appDelegate =(SanjeevKapoorAppDelegate *)[[UIApplication sharedApplication] delegate]; [appDelegate sopinglist]; ////[appDelegate recpies]; /// NSArray *a =[[appDelegate list1] componentsJoinedByString:@","]; k= [[appDelegate list1] componentsJoinedByString:@","];

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  • template typename question

    - by stephenteh
    Hi, I have a problem with template and wondering is there a possible way to achieve what I wanted to do. Here is my question. template <typename T> class A { public: typedef T* pointer; typedef const pointer const_pointer; A() {} template <typename D> A(const D& d) { // how can I store the D type // so I can refer it later on // outside of this function } };

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  • How to call a bool function...

    - by Gerri
    Hello, I did not see anything that address my particular code problem. I have a bool function in a class; the bool function is named: bool Triplet::operator ==(const Triplet& operand)const And I am trying to call it in Main but having problems just getting the call right. Apparently if I leave out any thing in the wording it gives an error that I have too few aruguments and if I try to use the entire wording of the function, I get the error that I need a semi-colon, but I already have a semi-colon at the end of the call, so I know that something else is wrong and I simply cannot figure out what is wrong! Any help would be appreciated! Thanks in advance.

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  • emacs: how do I use edebug on code that is defined in a macro?

    - by Cheeso
    I don't even know the proper terminology for this lisp syntax, so I don't know if the words I'm using to ask the question, make sense. But the question makes sense, I'm sure. So let me just show you. cc-mode (cc-fonts.el) has things called "matchers" which are bits of code that run to decide how to fontify a region of code. That sounds simple enough, but the matcher code is in a form I don't completely understand, with babckticks and comma-atsign and just comma and so on, and furthermore it is embedded in a c-lang-defcost, which itself is a macro. And I want to run edebug on that code. Look: (c-lang-defconst c-basic-matchers-after "Font lock matchers for various things that should be fontified after generic casts and declarations are fontified. Used on level 2 and higher." t `(;; Fontify the identifiers inside enum lists. (The enum type ;; name is handled by `c-simple-decl-matchers' or ;; `c-complex-decl-matchers' below. ,@(when (c-lang-const c-brace-id-list-kwds) `((,(c-make-font-lock-search-function (concat "\\<\\(" (c-make-keywords-re nil (c-lang-const c-brace-id-list-kwds)) "\\)\\>" ;; Disallow various common punctuation chars that can't come ;; before the '{' of the enum list, to avoid searching too far. "[^\]\[{}();,/#=]*" "{") '((c-font-lock-declarators limit t nil) (save-match-data (goto-char (match-end 0)) (c-put-char-property (1- (point)) 'c-type 'c-decl-id-start) (c-forward-syntactic-ws)) (goto-char (match-end 0))))))) I am reading up on lisp syntax to figure out what those things are and what to call them, but aside from that, how can I run edebug on the code that follows the comment that reads ;; Fontify the identifiers inside enum lists. ? I know how to run edebug on a defun - just invoke edebug-defun within the function's definition, and off I go. Is there a corresponding thing I need to do to edebug the cc-mode matcher code forms?

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  • C: using clock() to measure time in multi-threaded programs

    - by Shinka
    I've always used clock() to measure how much time my application took from start to finish, as; int main(int argc, char *argv[]) { const clock_t START = clock(); // ... const double T_ELAPSED = (double)(clock() - START) / CLOCKS_PER_SEC; } Since I've started using POSIX threads this seem to fail. It looks like clock() increases N times faster with N threads. As I don't know how many threads are going to be running simultaneously, this approach fails. So how can I measure how much time has passed ?

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  • win7 + vc7.1 + mfc = stackoverflow

    - by fogbit
    Hello! I've moved my vc7.1 project from WInXP to Win7. After rebuilding i got stackoverflow error in function _malloc_dbg when i start the program. "Unhandled exception at 0x0051bf0f in XXX.exe: 0xC00000FD: Stack overflow." Call stack: msvcr71d.dll!_malloc_dbg(unsigned int nSize=140, int nBlockUse=2, const char * szFileName=0x10267784, int nLine=163) msvcr71d.dll!_calloc_dbg(unsigned int nNum=1, unsigned int nSize=140, int nBlockUse=2, const char * szFileName=0x10267784, int nLine=163) msvcr71d.dll!_mtinit() msvcr71d.dll!_CRTDLL_INIT(void * hDllHandle=0x10200000, unsigned long dwReason=1, void * lpreserved=0x0018fd24) I tried to set up different stacksizes in project options (from 10 to 100 mbytes), in all cases i got this error. How can i fix this?

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  • About the String#substring() method

    - by alain.janinm
    If we take a look at the String#substring method implementation : new String(offset + beginIndex, endIndex - beginIndex, value); We see that a new String is created with the same original content (parameter char [] value). So the workaround is to use new String(toto.substring(...)) to drop the reference to the original char[] value and make it eligible for GC (if no more references exist). I would like to know if there is a special reason that explain this implementation. Why the method doesn't create herself the new shorter String and why she keeps the full original value instead? The other related question is : should we always use new String(...) when dealing with substring?

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