On 01/26/2016 06:25 PM, Alan Stern wrote: > On Tue, 26 Jan 2016, Chris Bainbridge wrote: > >> Booting 4.5.0-rc1 with new UBSAN checker enabled: >> >> [ 4.556968] >> ================================================================================ >> [ 4.556972] UBSAN: Undefined behaviour in drivers/usb/core/devio.c:1517:25 >> [ 4.556975] shift exponent -1 is negative > > Does a left shift by a negative amount matter if the result isn't used? >
By definition, any code with undefined behavior could do anything. But in practice, undefined shift just leads to undefined result of shift operation (it depends on operands and architecture). > Alan Stern >
