NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/6883

Internet Message Format | 1996-08-05 | 1.3 KB

Path: tor.teorfys.lu.se!coa
From: [e-mail] (Carl-Olof Almbadh)
Newsgroups: comp.lang.c
Subject: Re: void main() and other atrocities!
Date: 15 Feb 1996 23:20:09 GMT
Organization: Department of Theoretical Physics, Lund University
Message-ID: <4g0f39$[e-mail]>
References: <4eduaj$[e-mail]> <4em17r$[e-mail]> <6P/[e-mail]>
NNTP-Posting-Host: tor.teorfys.lu.se

In article <6P/[e-mail]>, [e-mail] (David C. Wright) writes:
|>
|> My understanding is that declarations such as
|>
|> char *(buffer1[2]);
|>
|> and
|>
|> char **buffer2;
|>
> differs in only one respect.  The constant 'buffer1' is an RVALUE. The
> variable 'buffer2' is an LVALUE.

In fact they are completely different. Both buffer1[i][j] and buffer2[i][j]
are l-values but the compiler computes their addresses in different ways.
The address of buffer1[i][j] is valuse stored is:
 buffer1 + (i+2 + j) * sizeof(char)
There is only one referencing.

In order to fetch buffer2[i][j] we must first fetch the char pointer
buffer2[i] from memory. This new value is then incremented by j*sizeof(char)
and one byte at the last address is fetched from memory.Thus there are
two pointers involved, both of which must be referenced to fetch a char.

Carl-OLof Almbladh
Lund Univ.
[e-mail]