Integer 16 is just a memory address. And also you can change your ID to be uintptr_t too: it is an integer in the end. You cannot cast away a const or volatile qualification. reinterpret_cast allows anything, that's usually a dangerous thing and normally reinterpret_cast is rarely used, tipically to convert pointers to/from integers Integer 16 is just a memory address. Expression reinterpret_cast(16) simply means "interpret the object at address 16 as type t ", but you k Theoretically, 16 could be replaced by any 4x (32bit) or 8x (64bit) integer. Reinterpret-cast Typecast. Copy link toncho11 commented Sep 11, 2019. It makes my alarm bells go off anyway. reinterpret_cast<> () is used for casting between unrelated types. All pointer conversions are allowed: neither the content pointed nor the pointer type itself is checked. It can also cast pointers to or from integer types. The format in which this integer value represents a pointer is platform-specific. It can typecast any pointer to any other data 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). reinterpret_cast is not an exception, which means that every time you specify function name as an operand, it gets implicitly converted to function pointer type. Understanding reinterpret_cast. Using the C++ reinterpret_cast, to re-interpret an int to unsigned int pointer . Expression reinterpret_cast (16) simply means "interpret the object at address 16 as type t ", but you know that there's no such t object at the address. This type of cast reinterprets the value of a variable of one type as another variable of a different type. The operation result is a simple binary copy of the value from one pointer to the other. The resulting value is the same as the value of expression. reinterpret_cast controls conversions between unrelated types, such as integers to pointers or pointers to other (unrelated) pointers. Given a type T and an lvalue expression x, the following two expressions for rvalue references have different syntax but the same semantics: reinterpret_cast(x) static_cast(*reinterpret_cast(&(x))) C++ also supports C-style casts. If this is your first visit, be sure to check out the FAQ by clicking the link above. 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). This is what the second warning is telling you. As you can see in the. And is suggested to use it using proper data type i.e., (pointer data type should be same as original data type). But it should not be something random or undefined. In the link you've posted there is the answer: Quote: reinterpret_cast only guarantees that if you cast a pointer to a different type, and then reinterpret_cast it back to the original type, you get the original value. Moreover, gcc-4.8.3 compiles this code just fine. Re-interpret cast can convert from an integer to pointer and vise versa. The expression reinterpret_cast(v)changes the interpretation of the value of the expression v. It can be used to convert between pointer and integer types, between unrelated pointer types, between pointer-to-member types, and between pointer-to-function types. You could say the same thing for Foo* and Bar* pointer types to any dissimilar structures.. static_cast means that a pointer of the source type can be used as a pointer of the destination type, which requires a subtype relationship. long long UniquePointer = static_cast (reinterpret_cast (&Param)); I can not test this on 32 bit platform right now, So I decided to ask here. Explanation. The simple answer is that you should NEVER cast an int to a class object pointer. Why do you think this is necessary?EDIT: Never mind, I re-read your post and now understand why you need to do it. int n = 0; char* c = reinterpret_cast(n); int another_value = reinterpret_cast(c); Why doesn't reinterpret_cast allow casting to simple formats? If we warn for loss of precision on both int->ptr and ptr->int, it becomes annoying. Param is just a class member field. This will only compile if the destination type is long enough. So on a machine using 8 byte pointers and 8 byte longs you could say: int * x; long y = (long)x;`. The result is implementation-defined and typically yields the numeric address of the byte in memory that the pointer pointers to. static_cast only allows conversions like int to float or base class pointer to derived class pointer. The reinterpret_cast operator produces a value of a new type that has the same bit pattern as its argument. int* a = new int(); void* b = reinterpret_cast(a); int* c = reinterpret_cast(b); a e c contengono lo stesso valore, ma il valore di b non specificato. An object pointer (including void*) or function pointer can be converted to an integer type using reinterpret_cast. It also allows casting from a pointer to an integer type and vice versa. A reinterpret_cast operator handles conversions between unrelated types. (It is possible that std::uintptr_t in does not exist, in which case you are either using pre-C++11 or, if not that, it would be a hint that the architecture does not allow for representing pointers as integer values. It should not be used to cast down a class hierarchy or to remove the const or volatile qualifiers. reinterpret_cast (it); you are telling the compiler to literally reinterpret the it object as a pointer. Whereas in. 11. What is reinterpret casting? static_cast only allows conversions like int to float or base class pointer to derived class pointer. 1 Reply > Using a char pointer to evaluate the variable one byte at a time, > rather than going through the entire chunk of data in one go. Your C++ learning is 0.00% complete. The resulting value is the same as the value of expression. Since the class holds this integer value and not a pointer value, it can be used as a constant expression. So cast to uintptr_t is a good idea. reinterpret_cast (ppDerived) is well defined. reinterpret_cast(x) turns off normal type checking between int and different pointer types, which are normally incompatible. You cannot cast away a const or volatile qualification. 1) An expression of integral, enumeration, pointer, or pointer-to-member type can be converted to its own type. reinterpret_cast (expr): The reinterpret_cast operator changes a pointer to any other type of pointer. Returns a value of type new-type. It is also known as indirection pointer used to dereference a pointer. 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. It is purely a compile-time directive which instructs the compiler to treat expression What is different here (But same in all cases! Dereferencing the result if it js a pointer to a pointer to derived is undefined behaviour, and not something you are permitted to do. You actually tell the compile "trust me, I know what I am doing". - type is a pointer reinterpreted as. Explanation. > If the answers are yes, I can send a patch. SQL Server Developer Center. Yes. 4 comments Comments. Otherwise, I'd like to > add comments to the code explaining why. You can use any other pointer, or you can use (size_t), which is 64 bits. reinterpret_cast is a very special and dangerous type of casting operator. To avoid truncating your pointer, cast it to a type of identical size. This operator can cast pointers between non-related classed. & (*it); the * is overloaded to do what you logically mean: convert the iterator type to its pointed-to object. If you choose 0, the macro can be simplified as: The only difference is that in the latter case, part of the expression is encapsulated in an inline constexpr function (addr). int a = 0x65000; int *i_ptr = reinterpret_cast (a); a = reinterpret_cast ( i_ptr); About our authors: Team EQA. ), is that the address of the objects are first static_casted to const A*, and then reinterpret_casted to std::uintptr_t. int *ptr; } This code shows how to declare a pointer in C++.All you have to do is an asterisk ( * ) before the pointer name. This cast operator can also convert variable into totally incompatible type too. It is used when we want to work with bits. Purpose for using reinterpret_cast . Re-interpreting an integer data type to an unsigned integer pointer using the C++ reinterpret_cast . However, compilation of the reinterpret_cast should fail if unsigned int is in fact too small. It contains the address of variable int i. The reinterpret_cast operator can convert any type of variable to fundamentally different type. The only safe conversion is to convert a pointer back to its original type. reinterpret_cast converts any pointer type to any other pointer type, even of unrelated classes. The operation result is a simple binary copy of the value from one pointer to the other. All pointer conversions are allowed: neither the content pointed nor the pointer type itself is checked. It can also cast pointers to or from integer types. United States (English) It is purely a compile-time directive which instructs the compiler to treat expression reinterpret_cast allows anything, that's usually a dangerous thing and normally reinterpret_cast is rarely used, tipically to convert pointers to/from integers 1. reinterpret_cast means reinterpret the underlying bit pattern. Anders: Cast it to INT_PTR instead.--David Wilkinson Visual C++ MVP. Login to check your learning progress. You may have to register before you can post: click the register link above to proceed. reinterpret_cast only guarantees that if you cast a pointer to a different type, and then reinterpret_cast it back to the original type, you get the original value. reinterpret_cast is for low-level casts that produce implementation-dependent (that is, non-portable) results, such as casting a pointer to an int . However, the optimizer may be restricted in what it can assume in the presence of a reinterpret_cast<> or C pointer cast. A value of integral or enumeration type to a pointer. Explanation. Compilation failed on Windows using: arm-none-eabi-g++.exe (GNU Tools for Arm Embedded Processors 8-2019-q3-update) 8.3.1 20190703 (release) [gcc-8-branch revision 273027] Console Output Skipping 179 KB - that the cast from pointer to int doesn't lose any information, i A special case is the so called "void-pointer" void pointer arithmetic is illegal in C programming, due to the absence of type activestate activestate. It is efficient because it does not copy the value. example. int *a;//pointer to int. Reinterpret casts are only available in C++ and are the least safe form of cast, allowing the reinterpretation of the underlying bits of a value into another type. When you use this cast you are saying to your compiler, 'I know better than you do, I want you to reinterpret the bit pattern of this object as a different type'. 3. new_data_type* pointer = reinterpret_cast < new_data_type* >( previous_data_type_ pointer ); Conversion is always explicit. 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). Example of Pointers in C.Illustration of pointers in C using following code:. reinterpret_cast< > ( ); "It appears to work fine" is one possible symptom of UB. The operation results is a simple binary 16 is the address we're assigning to the pointer, which lets us calculate the offset of the specified member. The address of a pointer is just a nu The value of *ptr will be value at address 0x77ff; that value would be 4. reinterpret_cast from integer to pointer; Forum Rule: Always post complete source code & details to reproduce any issue! 2. In cases of multiple inheritance reinterpret_cast will never perform delta arithmetic. Returns a value of type new_type.. C++: can't static_cast from double* to int* (4) Aside from being pointers, double* and int* have nothing in common. You can explicitly perform the following conversions: A pointer to any integral type large enough to hold it.
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