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  • In C, would !~b ever be faster than b == 0xff ?

    - by James Morris
    From a long time ago I have a memory which has stuck with me that says comparisons against zero are faster than any other value (ahem Z80). In some C code I'm writing I want to skip values which have all their bits set. Currently the type of these values is char but may change. I have two different alternatives to perform the test: if (!~b) /* skip */ and if (b == 0xff) /* skip */ Apart from the latter making the assumption that b is an 8bit char whereas the former does not, would the former ever be faster due to the old compare to zero optimization trick, or are the CPUs of today way beyond this kind of thing?

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  • What's the performance penalty of weak_ptr?

    - by Kornel Kisielewicz
    I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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  • Struct sockaddr, sin_family is not a member

    - by leon22
    According to this article from msdn ( http://msdn.microsoft.com/en-us/library/windows/desktop/ms740496(v=vs.85).aspx) the struct varies depending on which protocol is selected! Now I want to use this code from http://www.intelliproject.net/articles/showArticle/index/check_tcp_udp_port to check if a port is open or not! Now I have the struct sockaddr as follows: struct sockaddr { ushort sa_family; char sa_data[14]; }; but need this strcuture: struct sockaddr { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; }; Which changes are necessary? (Ws2_32.lib is linked and following includes #define WIN32_LEAN_AND_MEAN // sockets #include "windows.h" #include <winsock2.h> #include <ws2tcpip.h> Thx

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  • Console class in java Exception in reading password

    - by satheesh
    Hi, i am trying to use Console class in java. with this code import java.io.Console; public class ConsoleClass { public static void main(String[] args){ Console c=System.console(); char[] pw; pw=c.readPassword("%s","pw :"); for(char ch:pw){ c.format("%c",ch); } c.format("\n"); MyUtility mu =new MyUtility(); while(true){ String name=c.readLine("%s", "input?: "); c.format("output: %s \n",mu.doStuff(name)); } } } class MyUtility{ String doStuff(String arg1){ return "result is " +arg1; } } here i am getting NullPointerException when i tried to run in netbeans but i am not getting any Exception when tried to run in cmd with out netbeans IDE.Why?

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  • iPhone/Objective-C struct question my own CGRectZero

    - by Mark
    I am designing a Padding struct as follows: /* Padding. */ struct CGPadding { CGFloat left; CGFloat top; CGFloat right; CGFloat bottom; }; typedef struct CGPadding CGPadding; CG_INLINE CGPadding CGPaddingMake(CGFloat left, CGFloat top, CGFloat right, CGFloat bottom) { CGPadding p; p.left = left; p.top = top; p.right = right; p.bottom = bottom; return p; } This all works perfectly well, the problem is how can I create a const CGPadding CGPaddingZero? If I do like this: const CGPadding CGPaddingZero = (CGPadding){0.0, 0.0, 0.0, 0.0}; It doesnt work. So what am I doing wrong?

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  • How to implement best matching logic in TSQL (SQL Server 2000)

    - by sanjay-kumar1911
    I have two tables X and Y: Table X C1 C2 C3 1 A 13 2 B 16 3 C 8 Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 N 3 A 12 N 4 A 5 N 5 B 7 N 6 B 16 N 7 B 9 N 8 B 5 N 9 C 8 N 10 C 2 N 11 C 8 N 12 C 6 N Records in Table Y can be n number CREATE TABLE X(C1 INT, C2 CHAR(1), C3 INT); CREATE TABLE Y(C1 INT, C2 CHAR(1), C3 INT, C4 CHAR(1)); with following data: INSERT INTO X VALUES (1 'A',13 ); INSERT INTO X VALUES (2 'B',16 ); INSERT INTO X VALUES (3 'C',8 ); INSERT INTO Y VALUES (1,'A', 2,'N'); INSERT INTO Y VALUES (2,'A', 8,'N'); INSERT INTO Y VALUES (3,'A', 12,'N'); INSERT INTO Y VALUES (4,'A', 5,'N'); INSERT INTO Y VALUES (5,'B', 7,'N'); INSERT INTO Y VALUES (6,'B', 16,'N'); INSERT INTO Y VALUES (7,'B', 9,'N'); INSERT INTO Y VALUES (8,'B', 5,'N'); INSERT INTO Y VALUES (9,'C', 8,'N'); INSERT INTO Y VALUES (10,'C', 2,'N'); INSERT INTO Y VALUES (11,'C', 8,'N'); INSERT INTO Y VALUES (12,'C', 6,'N'); EXPECTED RESULT Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 Y 3 A 12 N 4 A 5 Y 5 B 7 N 6 B 16 Y 7 B 9 N 8 B 5 N 9 C 8 Y 10 C 2 N 11 C 8 N 12 C 6 N How do I compare value of column C3 in Table X with all possible matches of column C3 of Table Y and to mark records as matched and unmatched in column C4 of Table Y? Possible matches for A (i.e. value of column C2 in Table X) would be (where R is row number i.e. value of column C1 in Table Y): R1, R2, R3, R4, R1+R2, R1+R3, R1+R4, R2+R3, R2+R4, R3+R4, R4+R5, R1+R2+R3, R1+R2+R4, R2+R3+R4, R1+R2+R3+R4

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  • MFC: Reading entire file to buffer...

    - by deostroll
    I've meddled with some code but I am unable to read the entire file properly...a lot of junk gets appended to the output. How do I fix this? // wmfParser.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "wmfParser.h" #include <cstring> #ifdef _DEBUG #define new DEBUG_NEW #endif // The one and only application object CWinApp theApp; using namespace std; int _tmain(int argc, TCHAR* argv[], TCHAR* envp[]) { int nRetCode = 0; // initialize MFC and print and error on failure if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0)) { // TODO: change error code to suit your needs _tprintf(_T("Fatal Error: MFC initialization failed\n")); nRetCode = 1; } else { // TODO: code your application's behavior here. CFile file; CFileException exp; if( !file.Open( _T("c:\\sample.txt"), CFile::modeRead, &exp ) ){ exp.ReportError(); cout<<'\n'; cout<<"Aborting..."; system("pause"); return 0; } ULONGLONG dwLength = file.GetLength(); cout<<"Length of file to read = " << dwLength << '\n'; /* BYTE* buffer; buffer=(BYTE*)calloc(dwLength, sizeof(BYTE)); file.Read(buffer, 25); char* str = (char*)buffer; cout<<"length of string : " << strlen(str) << '\n'; cout<<"string from file: " << str << '\n'; */ char str[100]; file.Read(str, sizeof(str)); cout << "Data : " << str <<'\n'; file.Close(); cout<<"File was closed\n"; //AfxMessageBox(_T("This is a test message box")); system("pause"); } return nRetCode; }

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  • While making an RSS reader which saves articles, how can I prevent duplicates?

    - by Koning Baard
    Lets say I have a RSS feed which lists the 3 newest questions on SO. At 1 o'clock, the feed looks like this: While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ How to deploy a Java Swing application with an embedded JavaDB database? At 2 o'clock, this feed looks like: django url from another template than the one associated with the view-function While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ (duplicate articles are bold) I want to download the RSS feed every 5 minutes, parse it and save the articles that aren't already saved, but I do not want duplicates (items that remain in the new, updated feed like the examples above). What can I use to determine if an article is already saved? Thanks

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  • Should I call class destructor in this code?

    - by peterg
    I am using this sample to decode/encode some data I am retrieving/sending from/to a web server, and I want to use it like this: BOOL HandleMessage(UINT uMsg,WPARAM wParam,LPARAM lParam,LRESULT* r) { if(uMsg == WM_DESTROY) { PostQuitMessage(0); return TRUE; } else if(uMsg == WM_CREATE) { // Start timer StartTimer(); return TRUE; } else if(uMsg == WM_TIMER) { //get data from server char * test = "test data"; Base64 base64; char *temp = base64.decode(test); MessageBox(TEXT(temp), 0, 0); } } The timer is set every 5 minutes. Should I use delete base64 at the end? Does delete deallocates everything used by base64?

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  • Fseek on C problem

    - by Pedro
    i'm testing this code, but doesn't work, it always says that an error occurred :S int main(int argc, char **argv) { FILE *file_pointer; file_pointer = fopen("text.txt","r"); if(fseek(file_pointer, 0, -1)) { puts("An error occurred"); } else { char buffer[100]; fgets(buffer, 100, file_pointer); puts("The first line of the file is:"); puts(buffer); } fclose(file_pointer); return 0; }

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  • Why freed struct in C still has data?

    - by kliketa
    When I run this code: #include <stdio.h> typedef struct _Food { char name [128]; } Food; int main (int argc, char **argv) { Food *food; food = (Food*) malloc (sizeof (Food)); snprintf (food->name, 128, "%s", "Corn"); free (food); printf ("%d\n", sizeof *food); printf ("%s\n", food->name); } I still get 128 Corn although I have freed food. Why is this? Is memory really freed?

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  • grdb not working variables

    - by stupid_idiot
    hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake? I see the problem, dunno how to fix it yet though. The thing is, for some reason the instruction pointer starts at 0x100 and all the segment registers at 0x1628. To address the instruction the used combination is i guess [cs:ip] (one of the segment registers and the instruction pointer for sure). The offset to var1 is 0x10 (probably because from the begining of the code it's the 0x10th byte in order), i tried to examine the memory and what i got was: 1628:100 8 bytes 1628:108 8 bytes 1628:110 <- wtf? (assume another 8 bytes) 1628:118 ... whatever tricks are there in the memory [cs:var1] points somewhere else than in my code, which is probably where the label .data would usually address ds.... probably.. i don't know what is supposed to be at 1628:10 ok, i found out what caused the assness and wasted me whole fuckin day. the behaviour described above is just correct, the code is fully functional. what i didn't know is that grdb debugger for some reason sets the begining address to 0x100... the sollution is to insert the directive ORG 0x100 on the first line and that's the whole thing. the code was working because instruction pointer has the right address to first instruction and goes one by one, but your assembler doesn't know what effective address will be your program stored at so it pretty much remains relative to first line of the code which means all the variables (if not using label for data section) will remain pointing as if it started at 0x0. which of course wouldn't work with DOS. and grdb apparently emulates some DOS features... sry for the language, thx everyone for effort, hope this will spare someone's time if having the same problem... heheh.. at least now i know the reason why to use .data section :))))

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  • Primary reasons why programming language runtimes use stacks?

    - by manuel aldana
    Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • help me with xor encryption in c#

    - by x86shadow
    I wrote this code in c# to encrypt a text with a key : using System; using System.Linq; using System.Collections.Generic; using System.Text; namespace ENCRYPT { class XORENC { private static int Bin2Dec(string num) { int _num = 0; for (int i = 0; i < num.Length; i++) { _num += (int)Math.Pow(2, num.Length - i - 1) * int.Parse(num[i].ToString()); } return _num; } private static string Dec2Bin(int num) { if (num < 2) return num.ToString(); return Dec2Bin(num / 2) + (num % 2).ToString(); } public static string StrXor(string str, string key) { string _str = ""; string _key = ""; string _dec = ""; string _temp = ""; for (int i = 0; i < str.Length; i++) { _temp = Dec2Bin(str[i]); for (int j = 0; j < 8 - _temp.Length + 1; j++) { _temp = '0' + _temp; } _str += _temp; } for (int i = 0; i < key.Length; i++) { _temp = Dec2Bin(key[i]); for (int j = 0; j < 8 - _temp.Length + 1; j++) { _temp = '0' + _temp; } _key += _temp; } while (_key.Length < _str.Length) { _key += _key; } if (_key.Length > _str.Length) _key = _key.Substring(0, _str.Length); for (int i = 0; i < _str.Length; i++) { if (_str[i] == _key[i]) { _dec += '0'; } else { _dec += '1'; } } _str = ""; for (int i = 0; i < _dec.Length; i = i + 8) { char _chr = (char)0; _chr = (char)Bin2Dec(_dec.Substring(i, 8)); _str += _chr; } return _str; } } } the problem is that I always get error when I want to decrypt an encryted text with this code. see the example below for more info : string enc_text = ENCRYPT.XORENC("abc","a"); //enc_text = " ??" string dec_text = ENCRYPT.XORENC(enc_text,"a"); //ERROR any one can help ?

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  • C# StringBuilder question

    - by andrew
    in a C# file i have a class Archiver { [DllImport("Archiver.dll")] public static extern void archive(string data, StringBuilder response); } string data is an input, and StringBuilder response is where the function writes something the archive function prototype (written in C) looks like this: void archive(char * dataChr, char * outChr); and it receives a string in dataChr, and then does a strcpy(outChr,"some big text"); from C# i call it something like this: string message = "some text here"; StringBuilder response = new StringBuilder(10000); Archiver.archive(message,response); this works, but the problem, as you might see is that i give a value to the StringBuilder size, but the archive function might give back a (way) larger text than the size i've given to my StringBuilder. any way to fix this?

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  • abstract class in C++

    - by Alexander
    I have a derived derived class from an abstract class. The code is below. I have a FishTank class which is derived from an Aquarium and Aquarium is derived from item. My question is that should I put the definition of virtual int minWidth() const = 0; in aquarium again or is the code below sufficient? class Item{ public: virtual int minWidth() const = 0; }; class Aquarium{ public: virtual int calWidth() = 0; // Pure virtual function. }; class FishTank : public Aquarium{ public: FishTank(int base1, int base2, int height); ~FishTank(); int calWidth(); int minWidth(); };

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  • How to implement square root and exponentiation on arbitrary length numbers?

    - by tomp
    I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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  • Is there a way to use template specialization to separate new from new[]?

    - by Marlon
    I have an auto pointer class and in the constructor I am passing in a pointer. I want to be able to separate new from new[] in the constructor so that I can properly call delete or delete[] in the destructor. Can this be done through template specialization? I don't want to have to pass in a boolean in the constructor. template <typename T> class MyAutoPtr { public: MyAutoPtr(T* aPtr); }; // in use: MyAutoPtr<int> ptr(new int); MyAutoPtr<int> ptr2(new int[10]);

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  • How return a std::string from C's "getcwd" function

    - by rubenvb
    Sorry to keep hammering on this, but I'm trying to learn :). Is this any good? And yes, I care about memory leaks. I can't find a decent way of preallocating the char*, because there simply seems to be no cross-platform way. const string getcwd() { char* a_cwd = getcwd(NULL,0); string s_cwd(a_cwd); free(a_cwd); return s_cwd; } UPDATE2: without Boost or Qt, the most common stuff can get long-winded (see accepted answer)

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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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  • How to free memory in try-catch blocks?

    - by Kra
    Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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  • How to get Doxygen to recognize custom latex command

    - by Halpo
    Is there a way to use extra latex packages and/or extra latex commands with Doxygen code documentation system. For example I define the shortcut in a custom sty file. \newcommand{\tf}{\Theta_f} Then I use it about 300 time in the code, which is across about a dozen files. /*! Stochastic approximation of the latent response*/ void dual_bc_genw( //... double const * const psi, ///< \f$ \psi = B\tf \f$ //... ){/* lots of brilliant code */} But how do I get the system to recognize the extra package.

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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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