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  • Qt application crashing immediately without debugging info. How do I track down the problem?

    - by jjacksonRIAB
    I run an Qt app I've built: ./App Segmentation fault I run it with strace: strace ./App execve("./App", ["./App"], [/* 27 vars */]) = 0 --- SIGSEGV (Segmentation fault) @ 0 (0) --- +++ killed by SIGSEGV +++ Process 868 detached Again, no useful info. I run it with gdb: (gdb) run Starting program: /root/test/App Reading symbols from shared object read from target memory...(no debugging symbols found)...done. Loaded system supplied DSO at 0xffffe000 Program received signal SIGSEGV, Segmentation fault. 0x00000001 in ?? () Again, nothing. I run it with valgrind: ==948== Process terminating with default action of signal 11 (SIGSEGV) ==948== Bad permissions for mapped region at address 0x0 ==948== at 0x1: (within /root/test/App) Even if I put in debugging symbols, it doesn't give any more useful info. ldd shows all libraries being linked properly. Is there any other way I can find out what's wrong? I can't even do standard printf, cout, etc debugging. The executable doesn't even seem to start running at all. I rebuilt with symbols, and tried the suggestion below (gdb) break main Breakpoint 1 at 0x45470 (gdb) run Starting program: /root/test/App Breakpoint 1 at 0x80045470 Reading symbols from shared object read from target memory...done. Loaded system supplied DSO at 0xffffe000 Program received signal SIGSEGV, Segmentation fault. 0x00000001 in ?? () I checked for static initializers and I don't seem to have any. Yep, I tried printf, cout, etc. It doesn't even make it into the main routine, so I'm looking for problems with static initializers in link libraries, adding them in one-by-one. I'm not getting any stack traces either.

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  • Automatically creating C# wrappers from c headers?

    - by Winner
    Is there a way to automatically create p/invoke wrappers for .net from a c header? Of course I could create them by hand, but maintaining them would be painful, and I'd probably make a mistake somewhere resulting in hard to debug crashes. I tried SWIG, but it created full classes where simple structs would be sufficient. I'd prefer if the output worked on mono too, but that is not necessary.

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  • Can this extension method be improved?

    - by Newbie
    I have the following extension method public static class ListExtensions { public static IEnumerable<T> Search<T>(this ICollection<T> collection, string stringToSearch) { foreach (T t in collection) { Type k = t.GetType(); PropertyInfo pi = k.GetProperty("Name"); if (pi.GetValue(t, null).Equals(stringToSearch)) { yield return t; } } } } What it does is by using reflection, it finds the name property and then filteres the record from the collection based on the matching string. This method is being called as List<FactorClass> listFC = new List<FactorClass>(); listFC.Add(new FactorClass { Name = "BKP", FactorValue="Book to price",IsGlobal =false }); listFC.Add(new FactorClass { Name = "YLD", FactorValue = "Dividend yield", IsGlobal = false }); listFC.Add(new FactorClass { Name = "EPM", FactorValue = "emp", IsGlobal = false }); listFC.Add(new FactorClass { Name = "SE", FactorValue = "something else", IsGlobal = false }); List<FactorClass> listFC1 = listFC.Search("BKP").ToList(); It is working fine. But a closer look into the extension method will reveal that Type k = t.GetType(); PropertyInfo pi = k.GetProperty("Name"); is actually inside a foreach loop which is actually not needed. I think we can take it outside the loop. But how? PLease help. (C#3.0)

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  • Dependency Injection into your Singleton

    - by Langali
    I have a singleton that has a spring injected Dao (simplified below): public class MyService<T> implements Service<T> { private final Map<String, T> objects; private static MyService instance; MyDao myDao; public void set MyDao(MyDao myDao) { this. myDao = myDao; } private MyService() { this.objects = Collections.synchronizedMap(new HashMap<String, T>()); // start a background thread that runs for ever } public static synchronized MyService getInstance() { if(instance == null) { instance = new MyService(); } return instance; } public void doSomething() { myDao.persist(objects); } } My spring config will probably look like this: <bean id="service" class="MyService" factory-method="getInstance"/> But this will instantiate the MyService during startup. Is there a programmatic way to do a dependency injection of MyDao into MyService, but not have spring manage the MyService? Basically I want to be able to do this from my code: MyService.getInstance().doSomething(); while having spring inject the MyDao for me.

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  • Objects With No Behavior

    - by Patrick Donovan
    I've been teaching myself object oriented programming and I'm thinking about a situation where I have an object "Transaction", that has quite a few properties to it like account, amount, date, currency, type, etc. I never plan to mutate these data points, and calculation logic will live in other classes. My question is, is it poor Python design to instantiate thousands of objects just to hold data? I find the data far easier to work with embedded in a class rather than trying to cram it into some combination of data structures.

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  • Question about the evolution of interaction paradigm between web server program and content provider program?

    - by smwikipedia
    Hi experts, In my opinion, web server is responsible to deliver content to client. If it is static content like pictures and static html document, web server just deliver them as bitstream directly. If it is some dynamic content that is generated during processing client's request, the web server will not generate the conetnt itself but call some external proram to genearte the content. AFAIK, this kind of dynamice content generation technologies include the following: CGI ISAPI ... And from here, I noticed that: ...In IIS 7, modules replace ISAPI filters... Is there any others? Could anyone help me complete the above list and elabrate on or show some links to their evolution? I think it would be very helpful to understand application such as IIS, TomCat, and Apache. I once wrote a small CGI program, and though it serves as a content generator, it is still nothing but a normal standalone program. I call it normal because the CGI program has a main() entry point. But with the recenetly technology like ASP.NET, I am not writing complete program, but only some class library. Why does such radical change happens? Many thanks.

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  • Different behaviour of method overloading in C#

    - by Wondering
    Hi All, I was going through C# Brainteasers(http://www.yoda.arachsys.com/csharp/teasers.html) and came accross one question:what should be the o/p of below code class Base { public virtual void Foo(int x) { Console.WriteLine ("Base.Foo(int)"); } } class Derived : Base { public override void Foo(int x) { Console.WriteLine ("Derived.Foo(int)"); } public void Foo(object o) { Console.WriteLine ("Derived.Foo(object)"); } } class Test { static void Main() { Derived d = new Derived(); int i = 10; d.Foo(i); // it prints ("Derived.Foo(object)" } } but if I change the code to enter code here class Derived { public void Foo(int x) { Console.WriteLine("Derived.Foo(int)"); } public void Foo(object o) { Console.WriteLine("Derived.Foo(object)"); } } class Program { static void Main(string[] args) { Derived d = new Derived(); int i = 10; d.Foo(i); // prints Derived.Foo(int)"); Console.ReadKey(); } } I want to why the o/p is getting changde when we are inheriting vs not inheriting , why method overloading is behaving differently in both the cases

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  • Are these two functions the same?

    - by Ranhiru
    There is a function in the AES algorithm, to multiply a byte by 2 in Galois Field. This is the function given in a website private static byte gfmultby02(byte b) { if (b < 0x80) return (byte)(int)(b <<1); else return (byte)( (int)(b << 1) ^ (int)(0x1b) ); } This is the function i wrote. private static byte MulGF2(byte x) { if (x < 0x80) return (byte)(x << 1); else { return (byte)((x << 1) ^ 0x1b); } } What i need to know is, given any byte whether this will perform in the same manner. Actually I am worried about the extra conversion of to int and then again to byte. So far I have tested and it looks fine. Does the extra cast to int and then to byte make a difference?

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  • JNI cached jclass global reference variables being garbage collected?

    - by bubbadoughball
    I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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  • Fulltext searching array of strings

    - by Gotys
    I have a PHP array of strings: ie: "Big green car parked outside"..etc I would like to perform boolean search operations on these strings, similar to MySQL fulltext searching , or Sphinx Searching. For example, I would like to find all strings containing word "green" but not "car" Does anyone know of any existing PHP classes or libraries which would help me accomplish this ? Or can anyone suggest any google terms I could search for ? Thank you in advance!

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  • How to get around DnsRecordListFree error in .NET Framework 4.0?

    - by Greg Finzer
    I am doing an MxRecordLookup. I am getting an error when calling the DnsRecordListFree in the .NET Framework 4.0. I am using Windows 7. How do I get around it? Here is the error: System.MethodAccessException: Attempt by security transparent method to call native code through method. Here is my code: [DllImport("dnsapi", EntryPoint = "DnsQuery_W", CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)] private static extern int DnsQuery([MarshalAs(UnmanagedType.VBByRefStr)]ref string pszName, QueryTypes wType, QueryOptions options, int aipServers, ref IntPtr ppQueryResults, int pReserved); [DllImport("dnsapi", CharSet = CharSet.Auto, SetLastError = true)] private static extern void DnsRecordListFree(IntPtr pRecordList, int FreeType); public List<string> GetMXRecords(string domain) { List<string> records = new List<string>(); IntPtr ptr1 = IntPtr.Zero; IntPtr ptr2 = IntPtr.Zero; MXRecord recMx; try { int result = DnsQuery(ref domain, QueryTypes.DNS_TYPE_MX, QueryOptions.DNS_QUERY_BYPASS_CACHE, 0, ref ptr1, 0); if (result != 0) { if (result == 9003) { //No Record Exists } else { //Some other error } } for (ptr2 = ptr1; !ptr2.Equals(IntPtr.Zero); ptr2 = recMx.pNext) { recMx = (MXRecord)Marshal.PtrToStructure(ptr2, typeof(MXRecord)); if (recMx.wType == 15) { records.Add(Marshal.PtrToStringAuto(recMx.pNameExchange)); } } } finally { DnsRecordListFree(ptr1, 0); } return records; }

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  • Attempted to render a circle in opengl es 1.1, renders as oval

    - by eipxen
    Hi all, I attempted to render a circle in opengl es 1.1 as a test before building a larger program, but it renders as an oval. Here is the code I use to generate and render my vertices: static const int numVerts = 40; static GLfloat myFirstCircle[82]; myFirstCircle[0] = 0.0f; myFirstCircle[1] = 0.0f; for (int i = 2; i < (numVerts+1)*2; i+=2) { myFirstCircle[i] = .5 * cosf(i*2*3.14159/numVerts); myFirstCircle[i+1] = .5 * sinf(i*2*3.14159/numVerts); } glVertexPointer(2, GL_FLOAT, 0, myFirstCircle); glEnableClientState(GL_VERTEX_ARRAY); glDrawArrays(GL_TRIANGLE_FAN, 0, 22); I'm still somewhat new to this system, so I may have a silly error that I do not see, but it seems to me like this should generate 40 vertices on a circle of radius .5. When it renders, the shape on screen appears to be an oval, significantly taller than it is wide. My question is thus: why is my circle rendering this way, and what could I do to fix it? This is the first question on stackoverflow, so I'm not sure how to share an image of my output.

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  • Django admins disappearing from the admin index

    - by btol45
    We're running a Django website with rough 45 install Django admin classes. The handler is mod_fastcgi. Every once in a while about half the admins disappear from /admin/ screen. Touching the production.fcgi file restores everything to normal, but we have yet to determine the underling cause. Any thoughts on what the underlying issue might be?

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  • Why Enumerable.Range is faster than a direct yield loop?

    - by Morgan Cheng
    Below code is checking performance of three different ways to do same solution. public static void Main(string[] args) { // for loop { Stopwatch sw = Stopwatch.StartNew(); int accumulator = 0; for (int i = 1; i <= 100000000; ++i) { accumulator += i; } sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, accumulator); } //Enumerable.Range { Stopwatch sw = Stopwatch.StartNew(); var ret = Enumerable.Range(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } //self-made IEnumerable<int> { Stopwatch sw = Stopwatch.StartNew(); var ret = GetIntRange(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } } private static IEnumerable<int> GetIntRange(int start, int count) { int end = start + count; for (int i = start; i < end; ++i) { yield return i; } } } The result is like this: time = 306; result = 987459712 time = 1301; result = 987459712 time = 2860; result = 987459712 It is not surprising that "for loop" is faster than the other two solutions, because Enumerable.Aggregate takes more method invocations. However, it really surprises that "Enumerable.Range" is faster than the "self-made IEnumerable". I thought that Enumerable.Range will take more overhead than the simple GetIntRange method. What is the possible reason for this?

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  • Extend and Overload MS and Point Types

    - by dr d b karron
    Do I have make my own Point and Vector types to overload them ? Why does this not work ? namespace System . windows { public partial struct Point : IFormattable { public static Point operator * ( Point P , double D ) { Point Po = new Point ( ); return Po; } } } namespace SilverlightApplication36 { public partial class MainPage : UserControl { public static void ShrinkingRectangle ( WriteableBitmap wBM , int x1 , int y1 , int x2 , int y2 , Color C ) { wBM . DrawRectangle ( x1 , y1 , x2 , y2 , Colors . Red ); Point Center = Mean ( x1 , y1 , x2 , y2 ); wBM . SetPixel ( Center , Colors.Blue , 3 ); Point P1 = new Point ( x1 , y1 ); Point P2 = new Point ( x1 , y2 ); Point P3 = new Point ( x1 , y2 ); Point P4 = new Point ( x2 , y1 ); const int Steps = 10; for ( int i = 0 ; i < Steps ; i++ ) { double iF = (double)(i+1) / (double)Steps; double jF = ( 1.0 - iF ); Point P11 = **P1 * jF;** } }

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  • Why are enums considered compound types?

    - by FredOverflow
    Arrays, functions, pointers, references, classes, unions, enumerations and pointers to members are compound types. My understanding of a compound type is that is based on other type(s). For example, T[n], T* and T& are all based on T. Then what other type(s) is an enumeration based on? Or if my understanding of compound types is incorrect, what exactly is it about a type that makes it a compound type? Is compound simply a synonym for user-defined?

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  • In Selenium, how do I turn off logging?

    - by someguy
    I am using the following method: set_browser_log_level 'off' but my log level continues to include INFOs. I am trying to suppress both logging and the "Last 4 commands" display for when my test enters a login password. http://release.seleniumhq.org/selenium-remote-control/0.9.2/doc/ruby/classes/Selenium/SeleniumDriver.html#M000128

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  • Thread Management Object

    - by Gusdor
    I feel rather foolish as this is just a short question. I was reading about a bunch of thread management helper classes in .net, specifically one that aids the storage of threads to help a service manager object automatically invoke delegates onto the subscribing thread. I'm pretty sure it had something to do with creating dispatchers. Totally forgotten the name, can't find it :( Anyone know what I'm talking about?

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  • Visual Studio C#: Why is a "using" directive insufficient for some libraries?

    - by JYelton
    Scenario: I needed to add HttpUtility to my project, and I started by adding "using System.Web" to my collection of using directives. However the HttpUtility class would still not resolve, and I discovered (via this question) that I needed to add a reference to my project. Question: Why do I need to add a reference to this library when for most other classes a "using" directive will suffice?

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  • What exactly is a reentrant function?

    - by eSKay
    Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely on locks to singleton resources. Must not modify its own code (unless executing in its own unique thread storage) Must not call non-reentrant computer programs or routines. How is safely defined? If a program can be safely executed concurrently, does it always mean that it is reentrant? What exactly is the common thread between the six points mentioned that I should keep in mind while checking my code for reentrant capabilities? Also, Are all recursive functions reentrant? Are all thread-safe functions reentrant? Are all recursive and thread-safe functions reentrant? While writing this question, one thing comes to mind: Are the terms like reentrance and thread safety absolute at all i.e. do they have fixed concrete definations? For, if they are not, this question is not very meaningful. Thanks!

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  • Most Elegant Way to write isPrime in java

    - by Anantha Kumaran
    public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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