Path: utzoo!utgpu!water!watmath!clyde!att!gargoyle!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: malloc+copy+free vs realloc (was Efficient coding)
Message-ID: <14232@mimsy.UUCP>
Date: 29 Oct 88 02:54:45 GMT
References: <3105@hubcap.UUCP> <34112@XAIT.XEROX.COM> <1700@dataio.Data-IO.COM> <1730@dataio.Data-IO.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 19

In article <1730@dataio.Data-IO.COM> bright@Data-IO.COM (Walter Bright) writes:
-I've seen a number of people say that the following:
-	p = realloc(p,newsize);
-	assert(p);			/* fail if out of memory */
-is slower and/or less maintainable than:
-	newp = malloc(newsize);
-	assert(newp);			/* fail if out of memory */
-	memcpy(newp,p,(newsize < oldsize ? newsize : oldsize));
-	free(p);
-	oldsize = newsize;
-	p = newp;

Obviously this is false.  There is, however, one case where I do use
malloc+copy+free instead of realloc:  If the data are important and
must not be destroyed by a failed realloc.  The draft standard says
that this is already so; but I have my doubts about current implementations.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris