ptrdiff_t. A basic signed integer C/C++ type. The type's size is chosen so that it could store the maximum size of a theoretically possible array of any type. On a 32-bit system ptrdiff_t will take 32 bits and on a 64-bit one - 64 bits. In other words, a pointer can be safely put inside ptrdiff_t type (an exception is class-function-pointers but this is a special case). By the way the result of the expression where one pointer is subtracted from another (ptr1-ptr2) will have ptrdiff_t type. ptrdiff_t type is usually used for loop, array indexing, size storage and address arithmetic. ptrdiff_t type has its synonym intptr_t whose name indicates more clearly that it can store a pointer. In some cases using ptrdiff_t type is more effective and safe than using a more habitual for the programmer int type.
In the terms of static analyzer PVS-Studio, type ptrdiff_t refers to memsize-types. The analyzer includes Viva64 system for detailed error detection in 64-bit programs and for code optimization. Many diagnostic messages shown by Viva64 analyzer relate to recommendations on using memsize-types. Using memsize-types (such as size_t, ptrdiff_t, INT_PTR) instead of 32-bit types (int, unsigned) in 64-bit programs allows you to:
To learn more about the errors you can avoid when using ptrdiff_t type and also how this type allows improving and optimizing your 64-bit programs, see the articles given in the references.
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