Date: Tue, 6 Jan 1998 00:18:42 -0600 (CST) From: Joel Ray Holveck <joelh@gnu.org> To: steve@visint.co.uk Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Weird malloc problem. Message-ID: <199801060618.AAA04044@detlev.UUCP> In-Reply-To: <Pine.BSF.3.96.980105144332.15149A-100000@dylan.visint.co.uk> (message from Stephen Roome on Mon, 5 Jan 1998 14:54:19 %2B0000 (GMT)) References: <Pine.BSF.3.96.980105144332.15149A-100000@dylan.visint.co.uk>
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> I just discovered that I can happily malloc 512M without any problem, > even ps is sure that I've managed this, but seeing as I've only got about > 150M total virtual memory available I'm a bit surprised. Should I be ? IIRC (and I'm no expert), it is possible to sbrk your processes' entire addressable memory space (all 2^32 bits), and never use it. However, when you actually try to use it, then you get a core dump (I think a SIGSEGV). So, you call malloc, which sbrk's the block plus its overhead. Then malloc then puts its own before the block. At that point, then a actual page of virtual memory is assigned to the block, not before. I believe this is correct, but I could be mistaken. -- Joel Ray Holveck - joelh@gnu.org - http://www.wp.com/piquan Fourth law of programming: Anything that can go wrong wi sendmail: segmentation violation - core dumped
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