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Date: Tue, 5 Jun 2012 18:03:40 +0400
From: Andrey Chernov <ache@FreeBSD.ORG>
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Subject: Re: svn commit: r236582 - head/lib/libc/stdlib
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On Mon, Jun 04, 2012 at 09:34:49PM +0000, Andrey A. Chernov wrote:
>   1) IEEE Std 1003.1-2008, "errno" section, is explicit that
>   
>   "The setting of errno after a successful call to a function is
>   unspecified unless the description of that function specifies that
>   errno shall not be modified."
>   
>   However, free() in IEEE Std 1003.1-2008 does not mention its interaction
>   with errno, so MAY modify it after successful call
>   (it depends on particular free() implementation, OS-specific, etc.).

I see this subject brings some attention, so I prefer to exmpain details.
Here is the quote from the future standard change:
http://austingroupbugs.net/view.php?id=385

"However, earlier versions of this standard did not require this, and the
same example had to be written as:

    // buf was obtained by malloc(buflen)
    ret = write(fd, buf, buflen);
    if (ret < 0) {
        int save = errno;
        free(buf);
        errno = save;
        return ret;
    }
"

All we have now is "earlier version of standard". Until they'll publish 
future version, we need to stay this recommendation.

-- 
http://ache.vniz.net/