pointers

问题 Can I assume that a C/C++ struct pointer will always point to the first member? Example 1: typedef struct { unsigned char array_a[2]; unsigned char array_b[5]; }test; //.. test var; //.. In the above example will &var always point to array_a? Also in the above example is it possible to cast the pointer to an unsigned char pointer and access each byte separately? Example 2: function((unsigned char *)&var,sizeof(test)); //... //... void function(unsigned char *array, int len){ int i; for( i=0;

问题 Can I assume that a C/C++ struct pointer will always point to the first member? Example 1: typedef struct { unsigned char array_a[2]; unsigned char array_b[5]; }test; //.. test var; //.. In the above example will &var always point to array_a? Also in the above example is it possible to cast the pointer to an unsigned char pointer and access each byte separately? Example 2: function((unsigned char *)&var,sizeof(test)); //... //... void function(unsigned char *array, int len){ int i; for( i=0;

问题 Can I assume that a C/C++ struct pointer will always point to the first member? Example 1: typedef struct { unsigned char array_a[2]; unsigned char array_b[5]; }test; //.. test var; //.. In the above example will &var always point to array_a? Also in the above example is it possible to cast the pointer to an unsigned char pointer and access each byte separately? Example 2: function((unsigned char *)&var,sizeof(test)); //... //... void function(unsigned char *array, int len){ int i; for( i=0;

问题 I have this code: void caller() { char buffer[20][20]; int sd; ... send(sd, buffer[7], 5, 0); } Now I have this code: void funct(int sd, char **buffer) { send(sd, buffer[7], 5, 0); } void caller() { char buffer[20][20]; int sd; ... funct(sd, buffer); } To simplify suppose that instead of ... I have an initialization of socket UDP and connection with the server to use send instead of sendto. I don't understand why the second code generates on send an error and errno is set with value 14, but

问题 I have an account struct as below: type Account struct { Id string Name string Address string City string Email string Phone string Username string Password string IsActive bool } I also have two function: find and update . The find function find certain element from the slice and return the pointer to the element: func find(accounts []Account, username string) *Account { for _, acc := range accounts { if acc.IsActive && acc.Username == username { return &acc } } return nil } The update

问题 Here is some code that illustrates the question: #include <iostream> class Base { }; class Derived : public Base { }; void doThings(Base* bases[], int length) { for (int i = 0; i < length; ++i) std::cout << "Do ALL the things\n"; } int main(int argc, const char * argv[]) { Derived* arrayOfDerived[2] = { new Derived(), new Derived() }; doThings(arrayOfDerived, 2); // Candidate function not viable: no known conversion from 'Derived *[2]' to 'Base **' for 1st argument // Attempts to work out the

问题 In order to have better understanding of pointers, I'd like to have this cleared up. Different data types require different pointers, like char* or int* . Are all these pointers considered to be different data types or are they just the same data type? 回答1: Yes, they are different data types, as they point to different types of data. In other words, their usage and properties varies (example: same pointer arithmetic on different pointer type will yield different result) and they have

问题 From what I understand by now, I can say that a reference in C# is a kind of pointer to an object which has reference count and knows about the type compatibility. My question is not about how a value type is different than a reference type, but more about how a reference is implemented. I have read this post about what differences are between references and pointers, but that does not cover that much about what a reference is but it it's describing more it's properties compared with a

问题 From what I understand by now, I can say that a reference in C# is a kind of pointer to an object which has reference count and knows about the type compatibility. My question is not about how a value type is different than a reference type, but more about how a reference is implemented. I have read this post about what differences are between references and pointers, but that does not cover that much about what a reference is but it it's describing more it's properties compared with a

问题 From what I understand by now, I can say that a reference in C# is a kind of pointer to an object which has reference count and knows about the type compatibility. My question is not about how a value type is different than a reference type, but more about how a reference is implemented. I have read this post about what differences are between references and pointers, but that does not cover that much about what a reference is but it it's describing more it's properties compared with a