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Message-ID: <je4poyp4zh.fsf@sykes.suse.de> Date: Tue, 06 Mar 2007 20:05:38 +0100 From: Andreas Schwab <schwab@...e.de> To: "Chen, Dongliang" <Chen.D@...-t.com> Cc: <linux-kernel@...r.kernel.org> Subject: Re: return negative number for unsigned long function in kernel "Chen, Dongliang" <Chen.D@...-t.com> writes: > There are lots of functions in the Linux kernel that are declared as > unsigned long, but the return value is negative integer while error > occurred. An example of these functions is do_mmap_pgoff in mm/mmap.c, > which is defined as: > > unsigned long do_mmap_pgoff(....) > > In this function, it returns -ENODEV, -EPERM, -ENOMEM, -EINVAL, -EAGAIN, > -EACCESS depends on the error type. My question is how should the caller > perform error check based on the return value? The return value is directly passed to user space (it's the guts of the mmap syscall). The glibc wrapper transforms it appropriately so that errno is set and -1 is returned if there is an error. Andreas. -- Andreas Schwab, SuSE Labs, schwab@...e.de SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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