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• Cocoa - does CGDataProviderCopyData() actually copy the bytes? Or just the pointer?

  - by jtrim

  I'm running that method in quick succession as fast as I can, and the faster the better, so obviously if CGDataProviderCopyData() is actually copying the data byte-for-byte, then I think there must be a faster way to directly access that data...it's just bytes in memory. Anyone know for sure if CGDataProviderCopyData() actually copies the data? Or does it just create a new pointer to the existing data?

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• a class function with if(this==NULL) test got compiled?

  - by James

  I saw this code snippet during our lab and it actually compiles in MSVC2008 and G++. void LinkList< class T ::Insert(T n) { if (this == NULL) // some code here } As far as I know the this must not be null since you cannot call a class functions in c++ if it wasn't instantiated. Is this a valid code? if so what's the reason behind and where it can be useful?

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• How can I know where a Null Pointer Exception originated?

  - by navand

  I had a problem making a Blackberry app. I found some guy who made a tutorial which did what I attempted with mine. I copied the code of the tutorial's app to try and recreate it, just to see it in action. The result: Null Pointer Exception. I want to know what is triggering this. How can I?

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• What are the reasons for casting a void pointer?

  - by Maulrus

  I'm learning C++ from scratch, and as such I don't have an expert understanding of C. In C++, you can't cast a void pointer to whatever, and I understand the reasons behind that. However, I know that in C, you can. What are the possible reasons for this? It just seems like it's be a huge hole in type safety, which (to me) seems like a bad thing.

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• HOW CAN I COUNT ONLY NULL VALUES IN ORACLE/PLSQL???

  - by Dan F.

  HOW CAN I COUNT ONLY NULL VALUES IN ORACLE/PLSQL???... I want to count only the null values. Is there a function that does that?

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• How can i implement the NULL Object Design Pattern in a generic form?

  - by Colour Blend

  Is there a way to implement the null object design pattern in a generic form so that i don't need to implement it for every buisness object. For me, there are two high level classes you'll need for every business class. One for a single record and another for a list. So i think there should be a way to implement the NULL Object design pattern at a high level and not have to implement it for every class. Is there a way and how please?

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• Is it possible to have a function pointer to a template function in c++?

  - by LoudNPossiblyRight

  I want to know if it's possible to create a template function and then create a function pointer that points to that template function. Is this possible? I'm using VS2008, what's wrong with this code? template<typename T> T __cdecl tfunc(const T &x, const T &y){ return (x < y ? x : y); } int (*tfunc_ptr)(int, int) = &tfunc;

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• Can someone explain the difference between these two typedefs? (Function pointer related)

  - by Quicksilver

  This one is quite obviously a function pointer : typedef int (* foobar) (int a, unsigned char *b, unsigned int c); But what does this one do? typedef int (foobar *) (int a, unsigned char *b, unsigned int c);

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• Can I pass a pointer to a superclass, but create a copy of the child?

  - by Alex

  I have a function that takes a pointer to a superclass and performs operations on it. However, at some point, the function must make a deep copy of the inputted object. Is there any way I can perform such a copy? It occurred to me to make the function a template function and simply have the user pass the type, but I hold out hope that C++ offers a more elegant solution.

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• Does malloc(0) return a valid pointer or NULL?

  - by Jaspreet

  Hi Malloc() is used for dyamic memory allocation and returns a pointer (void*) to the memory allocated. What happens if i pass zero in malloc as an argument. Does a valid memory allocation takes place? Explain

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• c - why does it make sense that indexing a character pointer is an int?

  - by hatorade

  char *a = "apple"; printf("%s\n", a); \\ fine printf("%s\n", a[1]); \\ compiler complains an int is being passed Why does indexing a string pointer give me an int? I was expecting it to just print the string starting at position one (which is actually what happens when i use &a[1] instead). why do i need to get the address?

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• Check if a pointer points to allocated memory on the heap.

  - by Ugo

  Ok, I know this question seems to have been asked many times on stackoverflow. but please read Well the answer for any address is "No you can't" but the question here is to know if a pointer points to a piece of memory allocated with malloc/new. Actually I think it could be easily implemented overriding malloc/free and keeping track of allocated memory ranges. Do you know a memory management library providing this specific tool ?

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• C++ is it possible to set an object to null?

  - by John

  Further in my code, I check to see check if an object is null/empty. Is there a way to set an object to null?

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• Is there a tool that can check for null reference exceptions?

  - by ck

  Is there a tool available that can scan code and check for possible null reference exceptions, i.e. where there is no code to check for null before calling a method / accessing a property?

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• how to write an address (pointer) in a text file that can be read and dereferenced in C

  - by hatorade

  I would like to write an address in a text file, which can be read by fscanf and dereferenced by C after reading the pointer. How do I write the address in the file?

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• How to get a char* pointer to a C++ string?

  - by cambr

  I have a C++ string. I need to pass this string to a function accepting char* parameter, for example - strchr(). a) How do I get that pointer? b) Is there some funtion equivalent to strschr() that works for C++ strings?

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• Can I get a raw pointer from boost's weak_ptr?

  - by Czubaka

  Is it possible to get a raw pointer from boost::weak_ptr? Boost's shared_ptr has get() method and "-" operator. Is there some rationale behind weak_ptr not having the same functionality?

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• When pass-by-pointer is preferred to pass-by-reference in C++?

  - by skydoor

  I can imagine one case, in which the input parameter could be NULL so that pass-by-pointer is preferred but not pass-by-reference? Can anybody add more cases?

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• How to get exactly typeof is object/array/null..?

  - by 3gwebtrain

  var obj = {},ar = [],nothing=null,empty=undefined,word ='string',headorTail = true; console.log(typeof obj) //object console.log(typeof ar)//object console.log(typeof nothing)//object console.log(typeof empty)//undefined console.log(typeof word)//string console.log(typeof headorTail)//boolean But how can i get the type of obj,ar,nothing as "object, array,null" - what is the best way to achieve this?

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• Given an IBOutlet pointer in Objective-C/iPad, how do you hide that element?

  - by MikeN

  Given an IBOutlet pointer in Objective-C/iPad, how do you hide that element? Want to remove it from the screen by making it invisible, hiding it, removing it?

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• What CLR do when compare T with null, and T is a struct?

  - by Fujiy

  private static void SaveOrRemove<T>(string key, T value) { if (value == null) { Console.WriteLine("Remove: " +key); } .... } If I call passing 0 to value: SaveOrRemove("MyKey", 0), the condition (value == null) is false, then CLR dont make a (value == default(T)). What really happens?

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• How do i pass null into stdin like this perl code?

  - by acidzombie24

  This is my question and apparently this is the answer. I found you can stdout to null by writing NUL in command prompt so i tried writing < NUL at the end of my argument. No luck. How do i pass in null or do something with the IO locks like that perl code does so i can get my ffmpeg script not locking up after 15 or so seconds?

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• I propose we use a new standard pointer syntax for C++, any suggestions? [closed]

  - by Pirate for Profit

  Normally you would use a pointer as such: IMemLoc *loc = (IMemLoc*) new MemLoc(/* OFFSET */); HexScale *hexBaseScale = new HexScale(0x?????, 10); loc->scale(hexBaseScale); But this syntax is much cleaner, notice how we can scale easier: MemLoc *d = new MemLoc(/* OFFSET */); (*d).scale(new HexScale(0x?????, 10)) both of these will compile just a simple example, you know

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• Is it worth setting pointers to NULL in a destructor?

  - by Rob

  Imagine I have a class that allocates memory (forget about smart pointers for now): class Foo { public: Foo() : bar(new Bar) { } ~Foo() { delete bar; } void doSomething() { bar->doSomething(); } private: Bar* bar; }; As well as deleting the objects in the destructor is it also worth setting them to NULL? I'm assuming that setting the pointer to NULL in the destructor of the example above is a waste of time.

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• how to check null against a string in java?

  - by k38

  how to check null against a string in java? i am using stringname.equalsignorecase(null) but its not working.....

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