On 10/4/18 11:01 AM, Josef Wolf wrote: > On Thu, Oct 04, 2018 at 06:33:57AM -0600, Jeff Law wrote: >> On 10/4/18 6:19 AM, Josef Wolf wrote: >>> Why does gcc use those instructions? There is nothing special in the code >>> which is now translated into those trap instructions. I don't use floating >>> point at all, so I don't see any reason to use those instructions (and crash >>> on them). >>> >> GCC will replace a NULL pointer dereference or division by zero with a >> trap instruction. > > Is this described somewhere? I am pretty much sure that there is no NULL > pointer dereference and no division in this code. There must be something else. You can use -fdump-tree-all-blocks-details and look at the isolate-erroneous-paths dump file. Those are the cases I'm aware of where GCC will insert traps. > > In addition, the crash disappears, when I insert some no-op function call at > the beginning of one of those functions. This causes GCC to use other > registers for local variables. register allocation shouldn't have anything to do with whether or not something gets translated into a trap. jeff
