On Tue, 15 Jan 2008 14:46:57 -0600 Matt Mackall wrote: > > On Tue, 2008-01-15 at 11:10 -0800, Randy Dunlap wrote: > > On Tue, 15 Jan 2008 22:02:54 +0300 Anton Salikhmetov wrote: > > > > > 2008/1/15, Christoph Hellwig <[EMAIL PROTECTED]>: > > > > On Tue, Jan 15, 2008 at 07:02:44PM +0300, Anton Salikhmetov wrote: > > > > > > > @@ -33,71 +34,65 @@ asmlinkage long sys_msync(unsigned long start, > > > > > size_t len, int flags) > > > > > unsigned long end; > > > > > struct mm_struct *mm = current->mm; > > > > > struct vm_area_struct *vma; > > > > > - int unmapped_error = 0; > > > > > - int error = -EINVAL; > > > > > + int error = 0, unmapped_error = 0; > > > > > > > > > > if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) > > > > > - goto out; > > > > > + return -EINVAL; > > > > > if (start & ~PAGE_MASK) > > > > > - goto out; > > > > > + return -EINVAL; > > > > > > > > The goto out for a simple return style is used quite commonly in kernel > > > > code to have a single return statement which makes code maintaince, e.g. > > > > adding locks or allocations simpler. Not sure that getting rid of it > > > > makes a lot of sense. > > > > > > Sorry, I can't agree. That's what is written in the CodingStyle document: > > > > > > The goto statement comes in handy when a function exits from multiple > > > locations and some common work such as cleanup has to be done. > > > > CodingStyle does not try to cover Everything. Nor do we want it to. > > > > At any rate, there is a desire for functions to have a single point > > of return, regardless of the amount of cleanup to be done, so I agree > > with Christoph's comments. > > When we're not cleaning up resources, the main advantage of having a > single point of return is that you can trace backwards from the return > point through the function's logic. But that advantage flies right out > the window when you use gotos. You still have to figure out how you got > to the return statement by tracing back and looking at all the possible > gotos. And the "goto out" style adds bulk and non-negligible complexity > when we've got to search back for what the last explicitly set value of > "ret" or "error" or whatever the function in question is using was. > Sometimes people get this wrong ("retval is already -EINVAL, so I don't > need to explicitly set it"), and create bugs. > > So I think if we're not actually going to use "structured > programming" (no gotos) or "stack cleanup" styles, the single return > point style is more trouble than it's worth. > > A lesser advantage of the single return point is that you can set a > breakpoint or put a printk at the end of a function. But I don't think > that's much justification.
OTOH, I think that those are fine reasons for it. --- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/