UINTPTRMAX

UINTPTR_MAX is a macro defined in the C and C++ standard libraries that expands to the maximum value of the unsigned integer type uintptr_t. This type is intended to hold pointer values, enabling portable pointer-to-integer conversions when needed.

uintptr_t is an unsigned integer type defined to be large enough to hold a pointer. The macro is an implementation-defined constant expression of type uintptr_t and is provided by the standard headers. In practice, its exact value depends on the platform’s pointer width.

The value of UINTPTR_MAX varies with architecture. On typical 64-bit systems it is 18446744073709551615 (2^64 − 1), and on 32-bit systems it is 4294967295 (2^32 − 1). Some less common or specialized architectures may feature different widths, so the specific number can differ.

Relationship to other limits is practical but not guaranteed. SIZE_MAX, the maximum value of size_t, often equals UINTPTR_MAX because both sizes and pointers commonly share the same width, but this equivalence is not required by the standard.

Usage and purpose: UINTPTR_MAX is used in portable code where an upper bound on pointer-to-integer conversions or address-based calculations is needed. It helps with boundary checks, capacity computations, and safe casting between pointers and integers when performed carefully and in a well-defined manner.

In standard headers, the macro is named UINTPTR_MAX. In C it is provided by <stdint.h>; in C++ it is available through <cstdint>. Some nonstandard documentation or code may refer to UINTPTRMAX, but that spelling is not part of the standard.