Date: Tue, 12 Dec 2006 11:43:14 +1100 From: Andrew Reilly <andrew@areilly.bpc-users.org> (by way of Andrew Reilly <andrew-freebsd@areilly.bpc-users.org>) To: Dan Nelson <dnelson@allantgroup.com> Cc: Luigi Rizzo <rizzo@icir.org>, stable@freebsd.org Subject: Re: malloc(0) returns 0x800 on FreeBSD 6.2 ? Message-ID: <20061212114314.39542337@duncan.reilly.home> Resent-Message-ID: <20061212114439.42d40d48@duncan.reilly.home> In-Reply-To: <20061211182544.GG69299@dan.emsphone.com> References: <20061211094423.B44819@xorpc.icir.org> <20061211182544.GG69299@dan.emsphone.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 11 Dec 2006 12:25:44 -0600 Dan Nelson <dnelson@allantgroup.com> wrote: > The FreeBSD 6.x behaviour is slightly against POSIX rules that state > all successful malloc calls must return unique pointers, so the 7.x > malloc silently rounds zero-size mallocs to 1. Ideally malloc would > return unique pointers to blocks of memory set to MPROT_NONE via > mprotect() (you could fit 8192 of these pointers in an 8k page), to Could you, really? I'm not a language lawyer, and this is a language-lawyer question, but I would have expected that the maximal alignment rule would prevent you from allocating more than 512 or 1024 "unique, valid" pointers in a page. Perhaps there is no alignment requirement on a zero-byte object? Just curious. I don't care about the actual implementation, and I thought that handing out a special MPROT_NONE page was a good idea... > prevent applications from using that byte of memory. Cheers, -- Andrew
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20061212114314.39542337>