Schwarz, Konrad said: > While we're at it, I would be interested in the rational for "inventing" > ssize_t and not using ptrdiff_t instead, if anyone would care to > comment.
size_t has to be able to hold the size of the largest object. It is an unsigned type. ptrdiff_t has to be able to hold the largest difference between two pointers; it is a signed type. The two need not be a signed/unsigned pair. For example, if a system has a maximum object size of 64,000 bytes, then size_t needs to be at least 16 bits but ptrdiff_t needs to be at least 17 bits. Thus it would be legitimate for size_t to be (16 bit) unsigned short but ptrdiff_t to be (32 bit) signed int. ssize_t is the signed type corresponding to size_t. In the above example, it is required to be signed short. It's possible for a legitimate subtraction of two pointers to generate a value that can't fit in ssize_t. However, because size_t and ssize_t are a signed/unsigned pair, they have useful properties (for example, when dealing with varargs lists). -- Clive D.W. Feather | Work: <[EMAIL PROTECTED]> | Tel: +44 20 8495 6138 Internet Expert | Home: <[EMAIL PROTECTED]> | Fax: +44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 THUS plc | |
