pointers

问题 I wonder if C++ implementations are allowed to represent pointers to different types differently. For instance, if we had 4-byte sized/aligned int and 8-byte sized/aligned long , would it be possible to represent pointers-to- int / long as object addresses shifted right by 2/3 bits, respectively? This would effectively forbid to convert a pointer-to- long into a pointer-to- int . I am asking because of [expr.reinterpret.cast/7]: An object pointer can be explicitly converted to an object

问题 I know that the following is not correct: int arr[2][3] = {}; //some array initialization here int** ptr; ptr = arr; But I am quite surprised that the following lines actually work int arr[2][3] = {}; //some array initialization here auto ptr = arr; int another_arr[2][3] = {}; //some array initialization here ptr = another_arr; Can anyone possibly explain what is the type assigned to ptr in the second block of code, and what happened underneath? 回答1: Well, arrays decay to pointers when used

问题 I know that the following is not correct: int arr[2][3] = {}; //some array initialization here int** ptr; ptr = arr; But I am quite surprised that the following lines actually work int arr[2][3] = {}; //some array initialization here auto ptr = arr; int another_arr[2][3] = {}; //some array initialization here ptr = another_arr; Can anyone possibly explain what is the type assigned to ptr in the second block of code, and what happened underneath? 回答1: Well, arrays decay to pointers when used

问题 This question already has answers here : How to access a local variable from a different function using pointers? (10 answers) Closed 4 years ago . What happens when a pointer to a local variable is returned by a function? for example int* foo() { int local; int* ptr = &local; return ptr; } will compiler issue a warning or will it compile and produce unexpected results?? 回答1: Similar kind of question has already been asked : Stack Overflow, local pointer There are somethings in C which are

问题 This question already has answers here : How to access a local variable from a different function using pointers? (10 answers) Closed 4 years ago . What happens when a pointer to a local variable is returned by a function? for example int* foo() { int local; int* ptr = &local; return ptr; } will compiler issue a warning or will it compile and produce unexpected results?? 回答1: Similar kind of question has already been asked : Stack Overflow, local pointer There are somethings in C which are

问题 New to both stackoverflow and C/C++. Im working through implementing a binary tree and have a simple question. Lets say I have the following: struct Node { int data; Node* right_child; Node* left_child; }; void addNode(Node* tree, int new_data){ if(tree == NULL){ Node* new_tree = new Node; new_tree->data = new_data; new_tree->right_child = NULL; new_tree->left_child = NULL; tree = new_tree; } } int main(){ Node* tree = new Node; tree = NULL; addNode(tree, 3); cout << tree->data << endl; /

问题 Here is my Go program. package main import ( "fmt" ) type Person struct { Name string } func main() { p := &Person{"Jack"} // The following statement makes sense. We dereference the // pointer to reach the Person object and then retrieve its Name // field. fmt.Println((*p).Name) // But the following statement does not make sense. How does // this code work by retrieving the Name field directly from the // pointer without dereferencing it? fmt.Println(p.Name) } Here is the output. $ go run foo

问题 Could someone explain why self-written C++ exception, that inherit from exception return a char * and not a string? class myexception: public exception { virtual const char* what() const throw() { return "My exception happened"; } } myex; Source : http://www.cplusplus.com/doc/tutorial/exceptions/ 回答1: Since std::exception was designed as a base class for all exceptions, the interface is written in such a way that specializations do not require code that may throw. They may use it, but they do

问题 I'm using a threading library given to me at school and having trouble understanding how to pass a reference of an array of pointers to a method, or rather, I'm having trouble de-referencing and using the pointer array. The situation that I (believe I) understand is this: int main(void) { Foo* bar = new Foo(); // Passing instance of Foo pointer by reference CThread *myThread = new CThread(MyFunction, ACTIVE, &bar); return 0; } UINT __stdcall MyFunction(void *arg) { Foo* bar = *(Foo*)(arg);

问题 I'm using a threading library given to me at school and having trouble understanding how to pass a reference of an array of pointers to a method, or rather, I'm having trouble de-referencing and using the pointer array. The situation that I (believe I) understand is this: int main(void) { Foo* bar = new Foo(); // Passing instance of Foo pointer by reference CThread *myThread = new CThread(MyFunction, ACTIVE, &bar); return 0; } UINT __stdcall MyFunction(void *arg) { Foo* bar = *(Foo*)(arg);