[+cc Florian] On Wed, Mar 5, 2014 at 2:10 AM, David Laight <david.lai...@aculab.com> wrote: > From: Bjorn Helgaas >> With -Werror=array-bounds, gcc v4.7.x warns that in phy_find_valid(), the >> settings[] "array subscript is above array bounds", I think because idx is >> a signed integer and if the caller supplied idx < 0, we pass the guard but >> still reference out of bounds. > > Not rejecting the patch but... > > Just indexing an array with 'int' shouldn't cause this warning, > so somewhere a caller must actually be passing an idx < 0. > > While changing the type to unsigned will make the comparison > against the array bound reject the -1, I suspect that the > specific call path didn't really intend passing a hard-coded -1. > > It might be worth trying to locate the call site that passes -1.
I'm stumped. phy_find_valid() is static and only called from one place. The 'idx' argument is always the result of phy_find_setting(), which should always return something between 0 and ARRAY_SIZE(settings), so I don't see any way idx can be < 0. I stripped this down as far as I could; the resulting test code is at http://pastebin.com/pp1zMEWu if anybody else wants to look at it. I'm using gcc 4.8.x 20131105 (prerelease), with "-Warray-bounds -O2" flags. I hesitate to suspect a compiler bug, but it is very strange. For example, in my test code, replacing "MAX_NUM_SETTINGS" with "2" gets rid of the warnings. MAX_NUM_SETTINGS is known to be 2 at compile-time, so I don't know why this should make a difference. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
