Date: Thu, 20 Aug 1998 13:09:38 -0600 From: Warner Losh <imp@village.org> To: "Jordan K. Hubbard" <jkh@time.cdrom.com> Cc: dag-erli@ifi.uio.no (Dag-Erling Coidan =?iso-8859-1?Q?Sm=F8rgrav?= ), hackers@FreeBSD.ORG Subject: Re: Realloc fix for review Message-ID: <199808201909.NAA21884@harmony.village.org> In-Reply-To: Your message of "Thu, 20 Aug 1998 11:42:02 PDT." <25422.903638522@time.cdrom.com> References: <25422.903638522@time.cdrom.com>
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In message <25422.903638522@time.cdrom.com> "Jordan K. Hubbard" writes: : > Is that really a good idea? If you free the old block when realloc() : > fails, you lose whatever data was in it (and therefore potentially : > lose the ability to generate a sensible error message or recover : > gracefully). Such a change should be done on a per-case basis, rather : > than blindly applied to every snippet that calls realloc(). : : Hmmm. In my previous message, I'd also assumed that Warner was only : talking about changing instances of realloc() where the application : very definitely wanted the free-on-failure behavior. Replacing every : instance of realloc() with the new call would, indeed, be evil : incarnate given realloc()'s well-documented "I don't fondle the : previous value on failure" behavior. Heck, I thought that was the : entire reason for a new call in the first place. :-) No, this only replaces those places where the old pointer was destroyed rather than a s/realloc/frealloc/g. I was careful to only change those places where I knew that matched the pattern a = realloc(a,size); and didn't change those where they had: b = realloc(a,size); Since in the former case you've lost any reference to the old memory, the right thing to do is to free it up. Since I couldn't change realloc to have those semantics, I created frealloc which is easier to use than realloc() in the cases where you want the old memory freed when it can't allocate new memory. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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