On Thu, May 27, 2021 at 05:32:11PM +0200, Greg KH wrote: > On Fri, May 28, 2021 at 12:14:43AM +0900, Hyeonggon Yoo wrote: > > Hello, I was compiling kernel with make CC=clang-10 W=1 -s > > > > there are some places that compiler complains about > > pointer arithmetic like below.it says it's undefined behavior. > > > > is it just OK to use UBs like this (I hope it's not), > > or am I missing something? > > > > fs/kernfs/file.c:128:15: warning: performing pointer arithmetic on > > a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > > return NULL + !*ppos; > > Should work just fine, what problems have you found with that code? > Hello Greg. Yeah, that should work fine. I just wanted to understand warning that clang says! > Also happens in a few other places in the vfs layer. Tricky code, but > it works as pointer math is valid C code :) I'm searching about pointer arithmetic. Documents say that pointer math on void pointer (as NULL is void pointer) is illegal by C standards. (I can be missing something!) if above is true,then is it OK because it's valid on gcc and clang? Thanks, Hyeonggon _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
