This type of static_cast is used to implement move semantics in std::move . The reinterpret_cast operator converts a null pointer value to the null pointer value of the destination type. Following are some interesting facts about const_cast. As with al… Any program that mixes reinterpret_cast<> with pointers to void is, in fact, ill-formed. Type casting. reinterpret_cast treats all pointers exactly as traditional type-casting operators do. A static cast is used for conversions that are well defined like: cast less conversions, down conversion, conversions from void pointer, implicit type conversion, Re-interpret cast can convert from an integer to pointer and vise versa. There are four of them: 1.1. I suggest geting the standard and reading sections 5.2.9 (static_cast), and 5.2.10 (reinterpret_cast). But as §3.9 ¶2 explains (and §4.10 ¶2 reiterates), pointers to void are not pointers to object types. If the expression is a bit field lvalue, it is first converted to prvalue of the underlying type. Dynamic_cast and static_cast in C++. You should use it in cases like converting float to int, char to int, etc. 3) dynamic_cast does the job of static_cast, but does runtime checks to ensure the cast is good static_cast: This is used for the normal/ordinary type conversion. Returns a value of type new_type. Let’s look at what each of these casts do. static_cast is the main workhorse in our C++ casting world. static_cast handles implicit conversions between types (e.g. integral type conversion, any pointer type to void* ). static_cast can also call explicit conversion functions. reinterpret_cast is used, as the book mentions, for low-level hacks, especially when you know what you are doing, eg: static_cast and memory layout difference. One practical use of reinterpret_cast is in a hash function, which maps a value to an index in such a way that two distinct values rarely end up with the same index. The casting conversion is the general thing of the programming language because it converts from one type into another data type. The static_cast operator takes a single value as input, and outputs the same value converted to the type specified inside the angled brackets. Static_cast is best used to convert one fundamental type into another. While they look like template functions, they are part of the language itself, i.e.the behavior is implemented in the compiler, not in the standard library. C++: reinterpret_cast v.s. This is permitted via ¶7 of §5.2.10. (since C++11) 4) If new_type is the type void (possibly cv-qualified), static_cast discards the value of expression after evaluating it. Additionally, static_cast can also perform the following: Explicitly call a single-argument constructor or a conversion operator. In C++, reinterpret_cast, static_cast and const_cast is very common. static_cast in C++. Explanation. The destination void type can optionally include the const , volatile , or __unaligned attribute. We can do the common C-type I share the view that reinterpret_cast is more descriptive, however when it comes to casting to void* I'm less certain about the difference. reinterpret_cast converts one pointer to another without changing the address, or converts between pointers and their numerical (integer) values. They go into a lot of detail as to the differences between the two. e.g. 1) static_cast converts between types, doing "hidden" pointer math where appropriate 2) const_cast removes type qualifiers without doing any type conversion. Any expression can be explicitly converted to type void by the static_cast operator. 1) const_cast can be used to change non-const class members inside … For e.g. One can use reinterpret_cast<> for converting between pointers to object types. const_cast is pretty easy to understand as it doesn’t change the memory layout and just toggle the const flag for the compiler to help you do or avoid some checks. static_cast performs implicit conversions, the reverses of implicit standard conversions, and (possibly unsafe) base to derived conversions. The static_cast is used for the normal/ordinary type conversion. 2. static_cast 3. dynamic_cast 4. reinterpret_cast. c++ - Regular cast vs. static_cast vs. dynamic_cast . This is exactly where the C-Style is dangerous: As long as the full declaration is available, everything will work fine without any warning, but if you choose to forward-declare the types, the C-Style will still not emit a warning (while the static_cast will fail!) You should use it in cases like converting float to int, char to int, etc. The latter four are sometimes referred to as named casts. You can use reinterpret_cast to cast any pointer or integral type to any other pointer or integral type. Created attachment 39190 proposed patch. [] ExplanatioUnlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions. static_cast Applied to pointers to classes, that is to say that it allows to cast a pointer of a derived class to its base class (this is a valid conversion that can be implicitly performed) and it can also perform the inverse: cast a base class to its derivated class. If you want to perform any type of conversion that is based on compile-time (static) inference, this is the way to go. We will primarily use it for converting in places where implicit conversions fail, such as malloc. There are no runtime checks performed for static_cast conversions. static_cast cannot cast away const or volatile. reinterpret_cast is a compiler directive which tells the compiler to treat the current type as a new type. static_cast, const_cast, dynamic_cast, and reinterpret_cast all do distinctly different things. It would be useful for Clang (or anyone) to implement a new warning -Whidden-reinterpret-cast to diagnose any cast that acts as a reinterpret_cast without using that spelling. 1. const_cast const_cast is used to cast away the constness of variables. If new_type is an lvalue reference or an rvalue reference to function, the result is an lvalue. static_cast is meant to be used for cases which the compiler would automatically be able to convert, such as char to int and in your case A* to void*. reinterpret_cast converts between types by reinterpreting the underlying bit pattern. If new_type is an rvalue reference to object, the result is an xvalue. Convert to rvalue references. In C++, there are 5 different types of casts: C-style casts, static casts, const casts, dynamic casts, and reinterpret casts. reinterpret_cast 8 answers I've been writing C and C++ code for almost twenty years, but there'… We’ll cover C-style casts and static casts in this lesson. As we learnt in the generic types example, static_cast<> will fail if you try to cast an object to another unrelated class, while reinterpret_cast<> will always succeed by "cheating" the compiler to believe that the object is really that unrelated class. The reinterpret_cast operator (C++ only), Unlike static_cast, but like const_cast, the reinterpret_cast expression does not converted to an integer of sufficient size and back to the same pointer type is Syntax. reinterpret_cast. This is also the cast responsible for implicit type coersion and can also be called explicitly. from char to unsigned char (on this implementation) converts it to the. The static_cast operator converts a null pointer value to the null pointer value of the destination type. and perform a reinterpret_cast which will break your code. Explanation. One difference is that static_cast will perform conversions of one type to another using the standard conversion operators for the type being converted to, while reinterpret_cast does not. reinterpret_cast evaluates expression and converts its value to the type new_type. Unlike static_cast, but like const_cast, the reinterpret_cast expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). Neither static_cast nor reinterpret_cast can remove const from something. You cannot cast a const int* to an int* using either of these casts. For this, you would use a const_cast. A C-style cast of the form (T) is defined as trying to do a static_cast if possible, falling back on a reinterpret_cast if that doesn't work. static_cast should be used when you want to cast from a numeric type to other, from a BaseClass* to a DerivedClass* or from a void* to a specific Type*. Similarly, -Whidden-const-cast. This can cast related type classes. Convert any type to void, evaluating and discarding the value. Likewise, C++ has the following capabilities for explicit type conversions: 1. Change reinterpret_cast
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