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  • Thread-local storage segfaults on NetBSD only?

    - by bortzmeyer
    Trying to run a C++ program, I get segmentation faults which appear to be specific to NetBSD. Bert Hubert wrote the simple test program (at the end of this message) and, indeed, it crashes only on NetBSD. % uname -a NetBSD golgoth 5.0.1 NetBSD 5.0.1 (GENERIC) #0: Thu Oct 1 15:46:16 CEST 2009 +stephane@golgoth:/usr/obj/sys/arch/i386/compile/GENERIC i386 % g++ --version g++ (GCC) 4.1.3 20080704 prerelease (NetBSD nb2 20081120) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. % gdb thread-local-storage-powerdns GNU gdb 6.5 Copyright (C) 2006 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--netbsdelf"... (gdb) run Starting program: /home/stephane/Programmation/C++/essais/thread-local-storage-powerdns Program received signal SIGSEGV, Segmentation fault. 0x0804881b in main () at thread-local-storage-powerdns.cc:20 20 t_a = new Bogo('a'); (gdb) On other Unix, it works fine. Is there a known issue in NetBSD with C++ thread-local storage? #include <stdio.h> class Bogo { public: explicit Bogo(char a) { d_a = a; } char d_a; }; __thread Bogo* t_a; int main() { t_a = new Bogo('a'); Bogo* b = t_a; printf("%c\n", b->d_a); }

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  • What do I name this class whose sole purpose is to report failure?

    - by Blair Holloway
    In our system, we have a number of classes whose construction must happen asynchronously. We wrap the construction process in another class that derives from an IConstructor class: class IConstructor { public: virtual void Update() = 0; virtual Status GetStatus() = 0; virtual int GetLastError() = 0; }; There's an issue with the design of the current system - the functions that create the IConstructor-derived classes are often doing additional work which can also fail. At that point, instead of getting a constructor which can be queried for an error, a NULL pointer is returned. Restructuring the code to avoid this is possible, but time-consuming. In the meantime, I decided to create a constructor class which we create and return in case of error, instead of a NULL pointer: class FailedConstructor : public IConstructor public: virtual void Update() {} virtual Status GetStatus() { return STATUS_ERROR; } virtual int GetLastError() { return m_errorCode; } private: int m_errorCode; }; All of the above this the setup for a mundane question: what do I name the FailedConstructor class? In our current system, FailedConstructor would indicate "a class which constructs an instance of Failed", not "a class which represents a failed attempt to construct another class". I feel like it should be named for one of the design patterns, like Proxy or Adapter, but I'm not sure which.

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  • How to delete a QProcess instance correctly?

    - by Kopfschmerzen
    Hi everyone! I have a class looking like this: class FakeRunner : public QObject { Q_OBJECT private: QProcess* proc; public: FakeRunner(); int run() { if (proc) return -1; proc = new QProcess(); QStringList args; QString programName = "fake.exe"; connect(comp, SIGNAL(started()), this, SLOT(procStarted())); connect(comp, SIGNAL(error(QProcess::ProcessError)), this, SLOT(procError(QProcess::ProcessError))); connect(comp, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(procFinished(int, QProcess::ExitStatus))); proc->start(programName, args); return 0; }; private slots: void procStarted() {}; void procFinished(int, QProcess::ExitStatus) {}; void procError(QProcess::ProcessError); } Since "fake.exe" does not exist on my system, proc emits the error() signal. If I handle it like following, my program crashes: void FakeRunner::procError(QProcess::ProcessError rc) { delete proc; proc = 0; } It works well, though, if I don't delete the pointer. So, the question is how (and when) should I delete the pointer to QProcess? I believe I have to delete it to avoid a memory leak. FakeRunner::run() can be invoked many times, so the leak, if there is one, will grow. Thanks!

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  • Speedup writing C programs using a subset of the Python syntax

    - by psihodelia
    I am constantly trying to optimize my time. Writing a C code takes a lot of time and requires much more keyboard touches than say writing a Python program. However, in order to speed up the time required to create a C program, one can automatize many things. I'd like to write my programs using smth. like Python but with C semantics. It means, all keywords are C keywords, but syntax is optimized. For example, this C code: #include "dsplib.h" #include "coeffs.h" #define MODULENAME "dsplib" #define NUM_SAMPLES 320 typedef float t_Vec; typedef struct s_Inter { char *pc_Name; struct s_Inter *px_Next; }t_Inter; typedef struct s_DspLibControl { t_Vec f_Y; }t_DspLibControl; void v_DspLibName(void) { printf("Module: %s", MODULENAME); printf("\n"); } int v_DspLibInitInterControl(t_DspLibControl *px_Con) { int y; px_Con->f_Y = 0.0; for(int i=0;i<10;i++) { y += i * i; } return y; } in optimized pythonized version can look like: include dsplib, coeffs define MODULENAME="dsplib", NUM_SAMPLES=320 typedef float t_Vec typedef struct s_Inter: char *pc_Name struct s_Inter *px_Next t_Inter typedef struct s_DspLibControl: t_Vec f_Y t_DspLibControl v_DspLibName(): printf("Module: %s", MODULENAME); printf("\n") int v_DspLibInitInterControl(t_DspLibControl *px_Con): int y px_Con->f_Y = 0.0 for int i=0;i<10;i++: y += i * i return y My question is: Do you know any VIM script, which allows to translate an original pythonized C code into a standard C code? For example, one is writing a C code but uses pythonized syntax, once she decides to translate pythonized blocks into standard C, she selects such blocks and press some key. And she doesn't save such pythonized code of course, VIM translates it into standard C.

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  • String Manipulation: Splitting Delimitted Data

    - by Milli Szabo
    I need to split some info from a asterisk delimitted data. Data Format: NAME*ADRESS LINE1*ADDRESS LINE2 Rules: 1. Name should be always present 2. Address Line 1 and 2 might not be 3. There should be always three asterisks. Samples: MR JONES A ORTEGA*ADDRESS 1*ADDRESS2* Name: MR JONES A ORTEGA Address Line1: ADDRESS 1 Address Line2: ADDRESS 2 A PAUL*ADDR1** Name: A PAUL Address Line1: ADDR1 Address Line2: Not Given My algo is: 1. Iterate through the characters in the line 2. Store all chars in a temp variables until first * is found. Reject the data if no char is found before first occurence of asterisk. If some chars found, use it as the name. 3. Same as step 2 for finding address line 1 and 2 except that this won't reject the data if no char is found My algo looks ugly. The code looks uglier. Spliting using //* doesn't work either since name can be replaced with address line 1 if the data was *Address 1*Address2. Any suggestion?

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  • Binding type variables that only occur in assertions

    - by Giuseppe Maggiore
    Hi! I find it extremely difficult to describe my problem, so here goes nothing: I have a bunch of assertions on the type of a function. These assertions rely on a type variable that is not used for any parameter of the function, but is only used for internal bindings. Whenever I use this function it does not compile because, of course, the compiler has no information from which to guess what type to bind my type variable. Here is the code: {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances, FlexibleContexts, EmptyDataDecls, ScopedTypeVariables, TypeOperators, TypeSynonymInstances #-} class C a a' where convert :: a -> a' class F a b where apply :: a -> b class S s a where select :: s -> a data CInt = CInt Int instance S (Int,String) Int where select (i,_) = i instance F Int CInt where apply = CInt f :: forall s a b . (S s a, F a b) => s -> b f s = let v = select s :: a y = apply v :: b in y x :: Int x = f (10,"Pippo") And here is the generated error: FunctorsProblems.hs:21:4: No instances for (F a Int, S (t, [Char]) a) arising from a use of `f' at FunctorsProblems.hs:21:4-17 Possible fix: add an instance declaration for (F a Int, S (t, [Char]) a) In the expression: f (10, "Pippo") In the definition of `x': x = f (10, "Pippo") Failed, modules loaded: none. Prelude>

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  • Is it possible to store pointers in shared memory without using offsets?

    - by Joseph Garvin
    When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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  • EXPORT AS INSERT STATEMENTS: But in SQL Plus the line overrides 2500 characters!

    - by The chicken in the kitchen
    Hello, I have to export an Oracle table as INSERT STATEMENTS. But the INSERT STATEMENTS so generated, override 2500 characters. I am obliged to execute them in SQL Plus, so I receive an error message. This is my Oracle table: CREATE TABLE SAMPLE_TABLE ( C01 VARCHAR2 (5 BYTE) NOT NULL, C02 NUMBER (10) NOT NULL, C03 NUMBER (5) NOT NULL, C04 NUMBER (5) NOT NULL, C05 VARCHAR2 (20 BYTE) NOT NULL, c06 VARCHAR2 (200 BYTE) NOT NULL, c07 VARCHAR2 (200 BYTE) NOT NULL, c08 NUMBER (5) NOT NULL, c09 NUMBER (10) NOT NULL, c10 VARCHAR2 (80 BYTE), c11 VARCHAR2 (200 BYTE), c12 VARCHAR2 (200 BYTE), c13 VARCHAR2 (4000 BYTE), c14 VARCHAR2 (1 BYTE) DEFAULT 'N' NOT NULL, c15 CHAR (1 BYTE), c16 CHAR (1 BYTE) ); ASSUMPTIONS: a) I am OBLIGED to export table data as INSERT STATEMENTS; I am allowed to use UPDATE statements, in order to avoid the SQL*Plus error "sp2-0027 input is too long(2499 characters)"; b) I am OBLIGED to use SQL*Plus to execute the script so generated. c) Please assume that every record can contain special characters: CHR(10), CHR(13), and so on; d) I CAN'T use SQL Loader; e) I CAN'T export and then import the table: I can only add the "delta" using INSERT / UPDATE statements through SQL Plus.

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  • Closing a hook that captures global input events

    - by Margus
    Intro Here is an example to illustrate the problem. Consider I am tracking and displaying mouse global current position and last click button and position to the user. Here is an image: To archive capturing click events on windows box, that would and will be sent to the other programs event messaging queue, I create a hook using winapi namely user32.dll library. This is outside JDK sandbox, so I use JNA to call the native library. This all works perfectly, but it does not close as I expect it to. My question is - How do I properly close following example program? Example source Code below is not fully written by Me, but taken from this question in Oracle forum and partly fixed. import java.awt.AWTException; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.GridLayout; import java.awt.MouseInfo; import java.awt.Point; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JFrame; import javax.swing.JLabel; import com.sun.jna.Native; import com.sun.jna.NativeLong; import com.sun.jna.Platform; import com.sun.jna.Structure; import com.sun.jna.platform.win32.BaseTSD.ULONG_PTR; import com.sun.jna.platform.win32.Kernel32; import com.sun.jna.platform.win32.User32; import com.sun.jna.platform.win32.WinDef.HWND; import com.sun.jna.platform.win32.WinDef.LRESULT; import com.sun.jna.platform.win32.WinDef.WPARAM; import com.sun.jna.platform.win32.WinUser.HHOOK; import com.sun.jna.platform.win32.WinUser.HOOKPROC; import com.sun.jna.platform.win32.WinUser.MSG; import com.sun.jna.platform.win32.WinUser.POINT; public class MouseExample { final JFrame jf; final JLabel jl1, jl2; final CWMouseHook mh; final Ticker jt; public class Ticker extends Thread { public boolean update = true; public void done() { update = false; } public void run() { try { Point p, l = MouseInfo.getPointerInfo().getLocation(); int i = 0; while (update == true) { try { p = MouseInfo.getPointerInfo().getLocation(); if (!p.equals(l)) { l = p; jl1.setText(new GlobalMouseClick(p.x, p.y) .toString()); } Thread.sleep(35); } catch (InterruptedException e) { e.printStackTrace(); return; } } } catch (Exception e) { update = false; } } } public MouseExample() throws AWTException, UnsupportedOperationException { this.jl1 = new JLabel("{}"); this.jl2 = new JLabel("{}"); this.jf = new JFrame(); this.jt = new Ticker(); this.jt.start(); this.mh = new CWMouseHook() { @Override public void globalClickEvent(GlobalMouseClick m) { jl2.setText(m.toString()); } }; mh.setMouseHook(); jf.setLayout(new GridLayout(2, 2)); jf.add(new JLabel("Position")); jf.add(jl1); jf.add(new JLabel("Last click")); jf.add(jl2); jf.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent we) { mh.dispose(); jt.done(); jf.dispose(); } }); jf.setLocation(new Point(0, 0)); jf.setPreferredSize(new Dimension(200, 90)); jf.pack(); jf.setVisible(true); } public static class GlobalMouseClick { private char c; private int x, y; public GlobalMouseClick(char c, int x, int y) { super(); this.c = c; this.x = x; this.y = y; } public GlobalMouseClick(int x, int y) { super(); this.x = x; this.y = y; } public char getC() { return c; } public void setC(char c) { this.c = c; } public int getX() { return x; } public void setX(int x) { this.x = x; } public int getY() { return y; } public void setY(int y) { this.y = y; } @Override public String toString() { return (c != 0 ? c : "") + " [" + x + "," + y + "]"; } } public static class CWMouseHook { public User32 USER32INST; public CWMouseHook() throws UnsupportedOperationException { if (!Platform.isWindows()) { throw new UnsupportedOperationException( "Not supported on this platform."); } USER32INST = User32.INSTANCE; mouseHook = hookTheMouse(); Native.setProtected(true); } private static LowLevelMouseProc mouseHook; private HHOOK hhk; private boolean isHooked = false; public static final int WM_LBUTTONDOWN = 513; public static final int WM_LBUTTONUP = 514; public static final int WM_RBUTTONDOWN = 516; public static final int WM_RBUTTONUP = 517; public static final int WM_MBUTTONDOWN = 519; public static final int WM_MBUTTONUP = 520; public void dispose() { unsetMouseHook(); mousehook_thread = null; mouseHook = null; hhk = null; USER32INST = null; } public void unsetMouseHook() { isHooked = false; USER32INST.UnhookWindowsHookEx(hhk); System.out.println("Mouse hook is unset."); } public boolean isIsHooked() { return isHooked; } public void globalClickEvent(GlobalMouseClick m) { System.out.println(m); } private Thread mousehook_thread; public void setMouseHook() { mousehook_thread = new Thread(new Runnable() { @Override public void run() { try { if (!isHooked) { hhk = USER32INST.SetWindowsHookEx(14, mouseHook, Kernel32.INSTANCE.GetModuleHandle(null), 0); isHooked = true; System.out .println("Mouse hook is set. Click anywhere."); // message dispatch loop (message pump) MSG msg = new MSG(); while ((USER32INST.GetMessage(msg, null, 0, 0)) != 0) { USER32INST.TranslateMessage(msg); USER32INST.DispatchMessage(msg); if (!isHooked) break; } } else System.out .println("The Hook is already installed."); } catch (Exception e) { System.err.println("Caught exception in MouseHook!"); } } }); mousehook_thread.start(); } private interface LowLevelMouseProc extends HOOKPROC { LRESULT callback(int nCode, WPARAM wParam, MOUSEHOOKSTRUCT lParam); } private LowLevelMouseProc hookTheMouse() { return new LowLevelMouseProc() { @Override public LRESULT callback(int nCode, WPARAM wParam, MOUSEHOOKSTRUCT info) { if (nCode >= 0) { switch (wParam.intValue()) { case CWMouseHook.WM_LBUTTONDOWN: globalClickEvent(new GlobalMouseClick('L', info.pt.x, info.pt.y)); break; case CWMouseHook.WM_RBUTTONDOWN: globalClickEvent(new GlobalMouseClick('R', info.pt.x, info.pt.y)); break; case CWMouseHook.WM_MBUTTONDOWN: globalClickEvent(new GlobalMouseClick('M', info.pt.x, info.pt.y)); break; default: break; } } return USER32INST.CallNextHookEx(hhk, nCode, wParam, info.getPointer()); } }; } public class Point extends Structure { public class ByReference extends Point implements Structure.ByReference { }; public NativeLong x; public NativeLong y; } public static class MOUSEHOOKSTRUCT extends Structure { public static class ByReference extends MOUSEHOOKSTRUCT implements Structure.ByReference { }; public POINT pt; public HWND hwnd; public int wHitTestCode; public ULONG_PTR dwExtraInfo; } } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { new MouseExample(); } catch (AWTException e) { e.printStackTrace(); } } }); } }

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  • Best way to detect similar email addresses?

    - by Chris
    I have a list of ~20,000 email addresses, some of which I know to be fraudulent attempts to get around a "1 per e-mail" limit. ([email protected], [email protected], [email protected], etc...). I want to find similar email addresses for evaluation. Currently I'm using a levenshtein algorithm to check each e-mail against the others in the list and report any with an edit distance of less than 2. However, this is painstakingly slow. Is there a more efficient approach? The test code I'm using now is: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; namespace LevenshteinAnalyzer { class Program { const string INPUT_FILE = @"C:\Input.txt"; const string OUTPUT_FILE = @"C:\Output.txt"; static void Main(string[] args) { var inputWords = File.ReadAllLines(INPUT_FILE); var outputWords = new SortedSet<string>(); for (var i = 0; i < inputWords.Length; i++) { if (i % 100 == 0) Console.WriteLine("Processing record #" + i); var word1 = inputWords[i].ToLower(); for (var n = i + 1; n < inputWords.Length; n++) { if (i == n) continue; var word2 = inputWords[n].ToLower(); if (word1 == word2) continue; if (outputWords.Contains(word1)) continue; if (outputWords.Contains(word2)) continue; var distance = LevenshteinAlgorithm.Compute(word1, word2); if (distance <= 2) { outputWords.Add(word1); outputWords.Add(word2); } } } File.WriteAllLines(OUTPUT_FILE, outputWords.ToArray()); Console.WriteLine("Found {0} words", outputWords.Count); } } }

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  • How can I create a properly sizing QWebView?

    - by chacham15
    I want to make a QWebView appear expanding to the width and height so that ideally it will have no scroll bars. Some websites may have fixed widths that wont allow this, but I am not concerned with those. In any case, I cannot do as I wish because QWebView implements sizeHint as follows: QSize QWebView::sizeHint() const { return QSize(800, 600); // ####... } This is incorrect on a number of levels. 1. It doesnt at all take into account the size of the actual web page. 2. It doesnt take into account that the height and width are related to each other. (To prove #2 think about text in web pages that wraps to the next line.) As a simple fix I tried to do (where QResizingWebView extends QWebView): QSize QResizingWebView::sizeHint() const{ return this-page()-mainFrame()-contentsSize(); } While this is closer to the result, it also has 2 flaws. 1. It doesnt take into account the relation between the displayed width/height. 2. this->page()->mainFrame()->contentsSize() is inaccurate from what I can tell from my preliminary testing (it has returned heights larger than it should under many cases, although this may be related to #1). Does anyone have any tips to fix this?

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  • Why wont this compile its killing me. (java)

    - by Ryan The Leach
    import java.util.*; public class Caesar { public static void main(String [] args) { final boolean DEBUG = false; System.out.println("Welcome to the Caesar Cypher"); System.out.println("----------------------------"); Scanner keyboard = new Scanner (System.in); System.out.print("Enter a String : "); String plainText = keyboard.nextLine(); System.out.print("Enter an offset: "); int offset = keyboard.nextInt(); String cipherText = ""; for(int i=0;i<plainText.length();i++) { int chVal = plainText.charAt(i); if (DEBUG) {int debugchVal = chVal;} chVal +=offset; if (DEBUG) {System.out.print(chVal + "\t");} while (chVal <32 || chVal > 127) { if (chVal < 32) chVal += 96; if (chVal > 127) chVal -= 96; if(DEBUG) {System.out.print(chVal+" ");} } if (DEBUG) {System.out.println();} char c = (char) chVal; cipherText = cipherText + c; if (DEBUG) {System.out.println(i + "\t" + debugchVal + "\t" + chVal + "\t" + c + "\t" + cipherText);} } System.out.println(cipherText); } }

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  • Project Euler Problem #11

    - by SoulBeaver
    Source: http://projecteuler.net/index.php?section=problems&id=11 Quick overview: Take a 20x20 grid of numbers and compute the largest product of 4 pairs of numbers in either horizontal, vertical, or diagonal. My current approach is to divide the 20x20 grid up into single rows and single columns and go from there with a much more manageable grid. The code I'm using to divide the rows into rows is void fillRows ( string::const_iterator& fieldIter, list<int>& rowElements, vector<list<int>>& rows ) { int count(0); for( ; fieldIter < field.end(); ++fieldIter ) { if(isdigit(field[*fieldIter])) { rowElements.push_back(toInt(field[*fieldIter])); ++count; } if(count == 40) { rows.push_back(rowElements); count = 0; rowElements.clear(); } } } Short explanation: I have the field set as static const std::string field and I am filling a vector with lists of rows. Why a list? Because the queue doesn't have a clear function. Also practice using STL container lists and not ones I write myself. However, this thing isn't working. Oftentimes I see it omitting a character( function toInt parses the const char as int ) and I end up with 18 rows, two rows short of the 20x20 grid. The length of the rows seem good. Rows: 18 RowElements[0]: 40 (instead of pairs I saved each number individually. Will fix that later) What am I doing wrong?

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  • Where do I input a piece of code in Emacs?

    - by Vivi
    Hi there, I have just started using Emacs for the specific purpose of editing latex documents. I was attracted to Emacs because I want to be able to customize syntax highlighting even to the point of defining the colors of specific words. I am new to Emacs and not a programmer, so I having an extreme difficulty in doing what I want to do because most help I find assume too much knowledge for my level (it took me days just to be able to install emacs + auctex and change the first face color). I found something that I think will help me but I don't know how to do it. The post below is what I want to do, but what I am supposed to do with this code? Where should I insert it or where should I type it? I am using GNU Emacs in Windows. Thank you so much for you help :) M-x what-face will print the face found at the current point. And the code for that is: (defun what-face (pos) (interactive "d") (let ((face (or (get-char-property (point) 'read-face-name) (get-char-property (point) 'face)))) (if face (message "Face: %s" face) (message "No face at %d" pos)))) By the way, I found this in another post that can be found here: http://stackoverflow.com/questions/1242352/get-font-face-under-cursor-in-emacs

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  • Why are virtual methods considered early bound?

    - by AspOnMyNet
    One definition of binding is that it is the act of replacing function names with memory addresses. a) Thus I assume early binding means function calls are replaced with memory addresses during compilation process, while with late binding this replacement happens during runtime? b) Why are virtual methods also considered early bound (thus the target method is found at compile time, and code is created that will call this method)? As far as I know, with virtual methods the call to actual method is resolved only during runtime and not compile time?! thanx EDIT: 1) A a=new A(); a.M(); As far as I know, it is not known at compile time where on the heap (thus at which memory address ) will instance a be created during runtime. Now, with early binding the function calls are replaced with memory addresses during compilation process. But how can compiler replace function call with memory address, if it doesn’t know where on the heap will object a be created during runtime ( here I’m assuming the address of method a.M will also be at same memory location as a )? 2) v-table calls are neither early nor late bound. Instead there's an offset into a table of function pointers. The offset is fixed at compile time, but which table the function pointer is chosen from depends on the runtime type of the object (the object contains a hidden pointer to its v-table), so the final function address is found at runtime. But assuming the object of type T is created via reflection ( thus app doesn’t even know of existence of type T ), then how can at compile time exist an entry point for that type of object?

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  • Why execution of a portion of code loaded from external file is not halted by the OS?

    - by menjaraz
    I've harnessed a project released on internet a long time ago. Here comes the details, all irrelevant things being stripped off for sake of concision and clarity. A binary file whose content is descibed below HEX DUMP: 55 89 E5 83 EC 08 C7 45 FC 00 00 00 00 8B 45 FC 3B 45 10 72 02 EB 19 8B 45 FC 8B 55 0C 01 C2 8B 45 FC 03 45 08 8A 00 88 02 8D 45 FC FF 00 EB DD C6 45 FA 00 83 7D 10 01 76 6C 80 7D FA 00 74 02 EB 64 C6 45 FA 01 C7 45 FC 00 00 00 00 8B 45 10 48 39 45 FC 72 02 EB E2 8B 45 FC 8B 4D 0C 01 C1 8B 45 FC 03 45 0C 8D 50 01 8A 01 3A 02 73 30 8B 45 FC 03 45 0C 8A 00 88 45 FB 8B 45 FC 8B 55 0C 01 C2 8B 45 FC 03 45 0C 40 8A 00 88 02 8B 45 FC 03 45 0C 8D 50 01 8A 45 FB 88 02 C6 45 FA 00 8D 45 FC FF 00 EB A7 C9 C2 0C 00 90 90 90 90 90 90 is loaded into memory and executed using the following method snippet var MySrcArray, MyDestArray: array [1 .. 15] of Byte; // ... MyBuffer: Pointer; TheProc: procedure; SortIt: procedure(ASrc, ADest: Pointer; ASize: LongWord); stdcall; begin // Initialization of MySrcArray with random Bytes and display here ... // Instructions of loading of the binary file into MyBuffer using merely **GetMem** here ... @SortIt := MyBuffer; try SortIt(@MySrcArray, @MyDestArray, 15); // Display of MyDestArray (The outcome of the processing !) except // Invalid code error handling end; // Cleaning code here ... end; works like a charm on my box. My Question: How comes it works without using VirtualAlloc and/or VirtualProtect?

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  • How to provide js-ctypes in a spidermonkey embedding?

    - by Triston J. Taylor
    Summary I have looked over the code the SpiderMonkey 'shell' application uses to create the ctypes JavaScript object, but I'm a less-than novice C programmer. Due to the varying levels of insanity emitted by modern build systems, I can't seem to track down the code or command that actually links a program with the desired functionality. method.madness This js-ctypes implementation by The Mozilla Devs is an awesome addition. Since its conception, scripting has been primarily used to exert control over more rigorous and robust applications. The advent of js-ctypes to the SpiderMonkey project, enables JavaScript to stand up and be counted as a full fledged object oriented rapid application development language flying high above 'the bar' set by various venerable application development languages such as Microsoft's VB6. Shall we begin? I built SpiderMonkey with this config: ./configure --enable-ctypes --with-system-nspr followed by successful execution of: make && make install The js shell works fine and a global ctypes javascript object was verified operational in that shell. Working with code taken from the first source listing at How to embed the JavaScript Engine -MDN, I made an attempt to instantiate the JavaScript ctypes object by inserting the following code at line 66: /* Populate the global object with the ctypes object. */ if (!JS_InitCTypesClass(cx, global)) return NULL; /* I compiled with: g++ $(./js-config --cflags --libs) hello.cpp -o hello It compiles with a few warnings: hello.cpp: In function ‘int main(int, const char**)’: hello.cpp:69:16: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] hello.cpp:80:20: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] hello.cpp:89:17: warning: NULL used in arithmetic [-Wpointer-arith] But when you run the application: ./hello: symbol lookup error: ./hello: undefined symbol: JS_InitCTypesClass Moreover JS_InitCTypesClass is declared extern in 'dist/include/jsapi.h', but the function resides in 'ctypes/CTypes.cpp' which includes its own header 'CTypes.h' and is compiled at some point by some command during 'make' to yeild './CTypes.o'. As I stated earlier, I am less than a novice with the C code, and I really have no idea what to do here. Please give or give direction to a generic example of making the js-ctypes object functional in an embedding.

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  • No JSON object could be decoded - RPC POST call

    - by user1307067
    var body = JSON.stringify(params); // Create an XMLHttpRequest 'POST' request w/ an optional callback handler req.open('POST', '/rpc', async); req.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); req.setRequestHeader("Content-length", body.length); req.setRequestHeader("Connection", "close"); if (async) { req.onreadystatechange = function() { if(req.readyState == 4 && req.status == 200) { var response = null; try { response = JSON.parse(req.responseText); } catch (e) { response = req.responseText; } callback(response); } }; } // Make the actual request req.send(body); ---- on the server side ---- class RPCHandler(BaseHandler): '''@user_required''' def post(self): RPCmethods = ("UpdateScenario", "DeleteScenario") logging.info(u'body ' + self.request.body) args = simplejson.loads(self.request.body) ---- Get the following error on the server logs body %5B%22UpdateScenario%22%2C%22c%22%2C%224.5%22%2C%2230frm%22%2C%22Refinance%22%2C%22100000%22%2C%22740%22%2C%2294538%22%2C%2250000%22%2C%22owner%22%2C%22sfr%22%2C%22Fremont%22%2C%22CA%22%5D= No JSON object could be decoded: line 1 column 0 (char 0): Traceback (most recent call last): File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/_webapp25.py", line 703, in call handler.post(*groups) File "/base/data/home/apps/s~mortgageratealert-staging/1.357912751535215625/main.py", line 418, in post args = json.loads(self.request.body) File "/base/python_runtime/python_lib/versions/1/simplejson/init.py", line 388, in loads return _default_decoder.decode(s) File "/base/python_runtime/python_lib/versions/1/simplejson/decoder.py", line 402, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) File "/base/python_runtime/python_lib/versions/1/simplejson/decoder.py", line 420, in raw_decode raise JSONDecodeError("No JSON object could be decoded", s, idx) JSONDecodeError: No JSON object could be decoded: line 1 column 0 (char 0) --- firebug shows the following --- Parameters application/x-www-form-urlencoded ["UpdateScenario","c","4.... Source ["UpdateScenario","c","4.5","30frm","Refinance","100000","740","94538","50000","owner","sfr","Fremont","CA"] Based on the firebug report and also the logs shows self.request.body as anticipated. However simplejson load doesn't like it. Please help!

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  • Do I have to bind an UDP socket in my client program, to receive data? (I always get WASEINVAL)...

    - by Incubbus
    Hey There, I have the following problem: I am starting WSA, then I am creating a UDP socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP) and try to recvfrom on this socket, but it always returns -1 and I get WSAEINVAL (10022)... I don´t know why?... When I bind the port, that does not happen... But it is very lame to bind the clients socket... (As far as I remember, i never had this problem before:/ )... Anyone knows why this happens?... (I am sending data to my server, which anwsers[ or at least, tries to^^])... Inc::STATS CConnection::_RecvData(sockaddr* addr, std::string &strData) { int ret, len, fromlen; //return code / length of the data / sizeof(sockaddr) char *buffer; //will hold the data char c; //recv length of the message fromlen = sizeof(sockaddr); ret = recvfrom(m_InSock, &c, 1, 0, addr, &fromlen); if(ret != 1) { #ifdef __MYDEBUG__ std::stringstream ss; ss << WSAGetLastError(); MessageBox(NULL, ss.str().c_str(), "", MB_ICONERROR | MB_OK); #endif return Inc::ERECV; }...

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  • Stored procedure using cursor in mySql.

    - by RAVI
    I wrote a stored procedure using cursor in mysql but that procedure is taking 10 second to fetch the result while that result set have only 450 records so, I want to know that why that proedure is taking that much time to fetch tha record. procedure as below: DELIMITER // DROP PROCEDURE IF EXISTS curdemo123// CREATE PROCEDURE curdemo123(IN Branchcode int,IN vYear int,IN vMonth int) BEGIN DECLARE EndOfData,tempamount INT DEFAULT 0; DECLARE tempagent_code,tempplantype,tempsaledate CHAR(12); DECLARE tempspot_rate DOUBLE; DECLARE var1,totalrow INT DEFAULT 1; DECLARE cur1 CURSOR FOR select SQL_CALC_FOUND_ROWS ad.agentCode,ad.planType,ad.amount,ad.date from adplan_detailstbl ad where ad.branchCode=Branchcode and (ad.date between '2009-12-1' and '2009-12-31')order by ad.NUM_ID asc; DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET EndOfData = 1; DROP TEMPORARY TABLE IF EXISTS temptable; CREATE TEMPORARY TABLE temptable (agent_code varchar(15), plan_type char(12),sale double,spot_rate double default '0.0', dATE DATE); OPEN cur1; SET totalrow=FOUND_ROWS(); while var1 <= totalrow DO fetch cur1 into tempagent_code,tempplantype,tempamount,tempsaledate; IF((tempplantype='Unit Plan' OR tempplantype='MIP') OR tempplantype='STUP') then select spotRate into tempspot_rate from spot_amount where ((monthCode=vMonth and year=vYear) and ((agentCode=tempagent_code and branchCode=Branchcode) and (planType=tempplantype))); INSERT INTO temptable VALUES(tempagent_code,tempplantype,tempamount,tempspot_rate,tempsaledate); else INSERT INTO temptable(agent_code,plan_type,sale,dATE) VALUES(tempagent_code,tempplantype,tempamount,tempsaledate); END IF; SET var1=var1+1; END WHILE; CLOSE cur1; select * from temptable; DROP TABLE temptable; END // DELIMITER ;

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  • What is difference between my atoi() calls?

    - by Lucas
    I have a big number stored in a string and try to extract a single digit. But what are the differences between those calls? #include <iostream> #include <string> int main(){ std::string bigNumber = "93485720394857230"; char tmp = bigNumber.at(5); int digit = atoi(&tmp); int digit2 = atoi(&bigNumber.at(5)) int digit3 = atoi(&bigNumber.at(12)); std::cout << "digit: " << digit << std::endl; std::cout << "digit2: " << digit2 << std::endl; std::cout << "digit3: " << digit3 << std::endl; } This will produce the following output. digit: 7 digit2: 2147483647 digit3: 57230 The first one is the desired result. The second one seems to me to be a random number, which I cannot find in the string. The third one is the end of the string, but not just a single digit as I expected, but up from the 12th index to the end of the string. Can somebody explain the different outputs to me? EDIT: Would this be an acceptable solution? char tmp[2] = {bigNumber.at(5), '\0'}; int digit = atoi(tmp); std::cout << "digit: " << digit << std::endl;

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  • Experts help needed on libcurl programming in sending HTTP HEAD Request.

    - by Mani
    Hi all, I need clarifications on using libcurl for the following: I need to send an http HEAD request shown as below :: HEAD /mshare/3/30002:12:primary/stream_xNKNVH.mpeg HTTP/1.1 Host: 192.168.70.1:8080 Accept: */* User-Agent: Kreatel_IP-STB getcontentFeatures.dlna.org: 1 The code I wrote (shown below) , sends the HEAD Request in slightly different way: curl_global_init(CURL_GLOBAL_ALL); CURL* ctx = NULL; const char *url = "http://192.168.70.1:8080/mshare/3/30002:12:primary/stream_xNKNVH.mpeg" ; char *returnString; struct curl_slist *headers = NULL; ctx = curl_easy_init(); headers = curl_slist_append(headers,"Accept: /"); headers = curl_slist_append(headers,"User-Agent: Kreatel_IP-STB");\ headers = curl_slist_append(headers,"getcontentFeatures.dlna.org: 1"); headers = curl_slist_append(headers,"Pragma:"); headers = curl_slist_append(headers,"Proxy-Connection:"); curl_easy_setopt(ctx,CURLOPT_HTTPHEADER , headers ); curl_easy_setopt(ctx,CURLOPT_NOBODY ,1 ); curl_easy_setopt(ctx,CURLOPT_VERBOSE, 1); curl_easy_setopt(ctx,CURLOPT_URL,url ); curl_easy_setopt(ctx,CURLOPT_NOPROGRESS ,1 ); curl_easy_perform(ctx); curl_easy_cleanup(ctx); curl_global_cleanup(); The code shown above sends the HEAD Request in slightly different form (shown below) HEAD http://192.168.70.1:8080/mshare/3/30002:12:primary/stream_xNKNVH.mpeg HTTP/1.1 Host: 192.168.70.1:8080 Proxy-Connection: Keep-Alive Accept: */* User-Agent: Kreatel_IP-STB getcontentFeatures.dlna.org: 1 Can any one , share the appropriate code ?

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  • Binary files printing and desired precision

    - by yCalleecharan
    Hi, I'm printing a variable say z1 which is a 1-D array containing floating point numbers to a text file so that I can import into Matlab or GNUPlot for plotting. I've heard that binary files (.dat) are smaller than .txt files. The definition that I currently use for printing to a .txt file is: void create_out_file(const char *file_name, const long double *z1, size_t z_size){ FILE *out; size_t i; if((out = _fsopen(file_name, "w+", _SH_DENYWR)) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < z_size; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } I have three questions: Are binary files really more compact than text files?; If yes, I would like to know how to modify the above code so that I can print the values of the array z1 to a binary file. I've read that fprintf has to be replaced with fwrite. My output file say dodo.dat should contain the values of array z1 with one floating number per line. I have %.16Le up in my code but I think that %.15Le is right as I have 15 precision digits with long double. I have put a dot (.) in the width position as I believe that this allows expansion to an arbitrary field to hold the desired number. Am I right? As an example with %.16Le, I can have an output like 1.0047914240730432e-002 which gives me 16 precision digits and the width of the field has the right width to display the number correctly. Is placing a dot (.) in the width position instead of a width value a good practice? Thanks a lot...

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  • [MFC] Creating multiple dialogs in an MFC app with no main Window, they become children of each othe

    - by John
    (title updated) Following on from this question, now I have a clearer picture what's going on... I have a MFC application with no main window, which exposes an API to create dialogs. When I call some of these methods repeatedly, the dialogs created are parented to each other instead of all being parented to the desktop... I have no idea why. But anyway even after creation, I am unable to change the parent back to NULL or CWnd::GetDesktopWindow()... if I call SetParent followed by GetParent, nothing has changed. So apart from the really weird question of why Windows is magically parenting each dialog to the last one created, is there anything I'm missing to be able to set these windows as children of the desktop? UPDATED: I have found the reason for all this, but not the solution. From my dialog constructor, we end up in: BOOL CDialog::CreateIndirect(LPCDLGTEMPLATE lpDialogTemplate, CWnd* pParentWnd, void* lpDialogInit, HINSTANCE hInst) { ASSERT(lpDialogTemplate != NULL); if (pParentWnd == NULL) pParentWnd = AfxGetMainWnd(); m_lpDialogInit = lpDialogInit; return CreateDlgIndirect(lpDialogTemplate, pParentWnd, hInst); } Note: if (pParentWnd == NULL)pParentWnd = AfxGetMainWnd(); The call-stack from my dialog constructor looks like this: mfc80d.dll!CDialog::CreateIndirect(const DLGTEMPLATE * lpDialogTemplate=0x005931a8, CWnd * pParentWnd=0x00000000, void * lpDialogInit=0x00000000, HINSTANCE__ * hInst=0x00400000) mfc80d.dll!CDialog::CreateIndirect(void * hDialogTemplate=0x005931a8, CWnd * pParentWnd=0x00000000, HINSTANCE__ * hInst=0x00400000) mfc80d.dll!CDialog::Create(const char * lpszTemplateName=0x0000009d, CWnd * pParentWnd=0x00000000) mfc80d.dll!CDialog::Create(unsigned int nIDTemplate=157, CWnd * pParentWnd=0x00000000) MyApp.exe!CMyDlg::CMyDlg(CWnd * pParent=0x00000000) Running in the debugger, if I manually change pParentWnd back to 0 in CDialog::CreateIndirect, everything works fine... but how do I stop it happening in the first place?

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  • How to asynchronously read to std::string using Boost::asio?

    - by SpyBot
    Hello. I'm learning Boost::asio and all that async stuff. How can I asynchronously read to variable user_ of type std::string? Boost::asio::buffer(user_) works only with async_write(), but not with async_read(). It works with vector, so what is the reason for it not to work with string? Is there another way to do that besides declaring char user_[max_len] and using Boost::asio::buffer(user_, max_len)? Also, what's the point of inheriting from boost::enable_shared_from_this<Connection> and using shared_from_this() instead of this in async_read() and async_write()? I've seen that a lot in the examples. Here is a part of my code: class Connection { public: Connection(tcp::acceptor &acceptor) : acceptor_(acceptor), socket_(acceptor.get_io_service(), tcp::v4()) { } void start() { acceptor_.get_io_service().post( boost::bind(&Connection::start_accept, this)); } private: void start_accept() { acceptor_.async_accept(socket_, boost::bind(&Connection::handle_accept, this, placeholders::error)); } void handle_accept(const boost::system::error_code& err) { if (err) { disconnect(); } else { async_read(socket_, boost::asio::buffer(user_), boost::bind(&Connection::handle_user_read, this, placeholders::error, placeholders::bytes_transferred)); } } void handle_user_read(const boost::system::error_code& err, std::size_t bytes_transferred) { if ( err or (bytes_transferred != sizeof(user_)) ) { disconnect(); } else { ... } } ... void disconnect() { socket_.shutdown(tcp::socket::shutdown_both); socket_.close(); socket_.open(tcp::v4()); start_accept(); } tcp::acceptor &acceptor_; tcp::socket socket_; std::string user_; std::string pass_; ... };

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