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From: wirzeniu@cs.Helsinki.FI (Lars Wirzenius)
Newsgroups: comp.lang.c
Subject: Re: sizeof and multi-dimensional arrays
Message-ID: <10303@hydra.Helsinki.FI>
Date: 5 Jan 91 22:00:25 GMT
References: <4596@sactoh0.SAC.CA.US>
Sender: news@cs.Helsinki.FI
Organization: University of Helsinki, Department of Computer Science
Lines: 14

In article <4596@sactoh0.SAC.CA.US> jak@sactoh0.SAC.CA.US (Jay A. Konigsberg) writes:
>[ char x[5][6]; sizeof(*x) gives 6 ]
>sizeof(*x)   DOES NOT make sense. The size of a pointer on this machine
>	     is 4 bytes. (Note: adding "char *y; sizeof(y) does return 4).

But *x isn't a pointer, it's an array.  First the the type of x decays
from "array 5 of array 6 of char" into "pointer to array 6 of chars".
(See for example: _Standard_C_, by P.J.Plauger and Jim Brodie, page 74,
or K&R-2, Section A7.1, "Pointer Generation", page 200.)

This pointer is dereferenced with '*', and the result is an array of
type |char [6]|, which has the size 6.
--
Lars Wirzenius    wirzeniu@cs.helsinki.fi    wirzenius@cc.helsinki.fi