What you get for w is a pointer to the non exported type http.response but as ResponseWriter is an interface, that’s not visible. From server.go: type ResponseWriter interface { … } On the other hand, r is a pointer to a concrete struct, hence the need to pass a reference explicitly. From request.go: type Request … Read more
TL:DR: intptr_t might be best in some cases because the signed-overflow boundary is in the middle of the “non-canonical hole”. Treating a value as negative instead of huge may be better if wrapping from zero to 0xFF…FF or vice versa is possible, but pointer+size for any valid size can’t wrap a value from INT64_MAX to … Read more
Pointers are values just like let’s say int numbers. The difference is the interpretation of that value: pointers are interpreted as memory addresses, and ints are interpreted as integer numbers. When you want to change the value of a variable of type int, you pass a pointer to that int which is of type *int, … Read more
The error cannot use type []byte as type *[]byte in argument to sliceArr() comes from a typo which you haven’t posted (you tried to pass a slice and not a pointer to a slice to sliceArr()). As to the other error (cannot slice type *[]byte), you just need to use parenthesis to group the pointer … Read more
There is a major difference between slices and maps: Slices are backed by a backing array and maps are not. If a map grows or shrinks a potential pointer to a map element may become a dangling pointer pointing into nowhere (uninitialised memory). The problem here is not “confusion of the user” but that it … Read more
As mentioned, yes, the spec allows you to return either values (as non-pointers) or pointers. It’s just a decision you have to make. When to return pointer? Usually if the value you return is “more useful” as a pointer. When is it more useful? For example if it has many methods with pointer receiver. Yes, … Read more
Rust usually focuses on object value (i.e. the interesting part of the contents) rather than object identity (memory addresses). The implementation of Display for &T where T implements Display defers directly to the contents. Expanding that macro manually for the String implementation of Display: impl<‘a> Display for &’a String { fn fmt(&self, f: &mut Formatter) … Read more
that references don’t implement Deref You can see all the types that implement Deref, and &T is in that list: impl<‘a, T> Deref for &’a T where T: ?Sized The non-obvious thing is that there is syntactical sugar being applied when you use the * operator with something that implements Deref. Check out this small … Read more
The probably unsatisfying answer is “you can’t do it because the spec says so.” The spec says that to use & on something it has to be addressable or a compound literal, and to be addressable it has to be “a variable, pointer indirection, or slice indexing operation; or a a field selector of an … Read more
Whenever a method wants to modify the receiver, it must be a pointer to the value; the method must have a pointer receiver. If a method has a non-pointer receiver, a copy will be made and passed when that method is called. From that point, no matter what you do with the receiver, you can … Read more