The C and C++ standards do not support this feature. However, the GNU Compiler Collection (GCC) includes a non-standard extension for doing this, as described in the Labels as Values section of the Using the GNU Compiler Collection manual. Essentially, they have added a special unary operator && that reports the address of the label … Read more
Reviewing the basic terminology It’s usually good enough – unless you’re programming assembly – to envisage a pointer containing a numeric memory address, with 1 referring to the second byte in the process’s memory, 2 the third, 3 the fourth and so on…. What happened to 0 and the first byte? Well, we’ll get to … Read more
The code produces undefined behavior, because it attempts to dereference an uninitialized pointer. Undefined behavior is unpredictable and follows no logic whatsoever. For this reason, any questions about why your code does something or doesn’t do something make no sense. You are asking why it runs? It doesn’t run. It produces undefined behavior. You are … Read more
Modern compilers typically implement the (Named) Return Value Optimization, by which the copy you reference (and would logically expect) is not done. Ever since Visual Studio 2005 (VC++ 8.0) I don’t think twice about returning objects.
Because these are the rules (standards) of the language. There’s nothing telling you it’s possible to initialize a pointer with an array like this, for example, the following is also illegal: char* name={‘m’, ‘i’, ‘k’, ‘h’, ‘i’, ‘l’, 0}; A literal string gets its own treatment and is not defined just as an array of … Read more
[*] As most times, the compiler is right and intuition wrong. The problem is that if that particular assignment was allowed you could break const-correctness in your program: const int constant = 10; int *modifier = 0; const int ** const_breaker = &modifier; // [*] this is equivalent to your code *const_breaker = & constant; … Read more
The cast itself is fine. What might indeed be questionable would be using a pointer to an element within one subarray to access elements in a different one: While the operation is clearly well-defined at a lower level (everything’s aligned properly, no padding, the types match, …), my impression of the C standard has been … Read more
::* denotes a Pointer to member. With the surrounding code it’s actually a Pointer to member function. Status_e(MyClass::*)(TupleInfo & info) is a member function of class MyClass, returning Status_e, and having one parameter TupleInfo&. (The argument name info is useless here but obviously silently ignored by the compiler.) The other snippet in OP’s question shows … Read more
I needed to define this callback: typedef void (*MIDIReadProc) ( const MIDIPacketList *pktlist, void *readProcRefCon, void *srcConnRefCon ); and I wanted to use Objective-C as least as possible. This was my approach: MIDIReadProcCallback.h #import <Foundation/Foundation.h> #import <AudioToolbox/AudioToolbox.h> typedef void (^OnCallback)(const MIDIPacketList *packetList); @interface MIDIReadProcCallback : NSObject + (void (*)(const MIDIPacketList *pktlist, void *readProcRefCon, void *srcConnRefCon))midiReadProc; … Read more
When you call a function or a method and you pass parameters to it, a copy is made from the values, and the function can only access these copies. This means if the function attempts to modify / change the copies, it will not change the original value. For example: func main() { i := … Read more