MSP430 IAR C/C++ Compiler reference guide - Rice University

Pointer typesDATA POINTERSThe following data pointers are available:Keyword Pointer size Index type Address range__data16 16 bits signed int 0x0–0xFFFF__data20 * 20 bits signed int 0x0–0xFFFFFTable 32: Data pointers* The __data20 pointer type is not available in the Small data model.CASTINGCasts between pointers have the following characteristics:●●●●●●●●Casting a value of an integer type to a pointer of a smaller type is performed bytruncationCasting a value of an integer type to a pointer of a larger type is performed by zeroextensionCasting a pointer type to a smaller integer type is performed by truncationCasting a pointer type to a larger integer type is performed by zero extensionCasting a data pointer to a function pointer and vice versa is illegalCasting a function pointer to an integer type gives an undefined resultCasting from a smaller pointer to a larger pointer is performed by zero extensionCasting from a larger pointer to a smaller pointer is performed by truncation.size_tsize_t is the unsigned integer type required to hold the maximum size of an object. Forthe MSP430 architecture, and for the MSP430X architecture in the Small and Mediumdata models, the size of size_t is 16 bits. In the Large data model, the size of size_tis 32 bits.ptrdiff_tptrdiff_t is the type of the signed integer required to hold the difference between twopointers to elements of the same array. For the MSP430 architecture, and for theMSP430X architecture in the Small and Medium data models, the size of ptrdiff_tis 16 bits. In the Large data model, the size of ptrdiff_t is 32 bits.Note: Subtracting the start address of an object from the end address can yield anegative value, because the object can be larger than what the ptrdiff_t can represent.174MSP430 IAR C/C++ CompilerReference Guide