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From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c
Subject: Re: Array bounds checking with C????
Message-ID: <2693@dataio.Data-IO.COM>
Date: 7 Sep 90 18:32:33 GMT
References: <DAVEG.90Aug31224630@near.cs.caltech.edu> <1589@redsox.bsw.com> <1340@ontek.com>
Organization: Data I/O Corporation; Redmond, WA
Lines: 17

In comp.lang.c, campbell@redsox.bsw.com (Larry Campbell) writes:
| Are there actually any current compilers out there that are so stupid 
| that they generate substantially different code for the following two 
| code fragments? 
| 
|     /* Fragment 1 */
|     for (p = array; p < &array[ARRAY_SIZE]; p++)
| 	*p = '\0';		/* changed from *p++ = 0;	*/
| 
|     /* Fragment 2 */
|     for (i = 0; i < ARRAY_SIZE; i++)
| 	array[i] = '\0';

The optimization that converts 2 to 1 is called 'strength reduction'
with 'loop induction variable elimination'. It is an advanced capability
of global optimizing compilers, and few compilers do it. Zortech C/C++
does this optimization when it is compiling with full optimization.