On Tue, Jun 30, 2015 at 08:58:26AM -0600, Simon Glass wrote:
Hi,
On 29 June 2015 at 22:18, Kushwaha Prabhakar prabhakar@freescale.com wrote:
Hi Simon, Tom,
-fdelete-null-pointer-checks flag controls global dataflow analyses and eliminate useless checks for null pointers; It assume that if a pointer is checked after it has already been dereferenced, it cannot be null. This flag is enabled by default. gcc v4.9 has more optimizations added to this option. Hence it is very aggressive with GCC v4.9 series. It is also well documented in the GCC v4.9 release notes: https://gcc.gnu.org/gcc-4.9/porting_to.html
There is possibility after moving to gcc-4.9 some platform may/may not work properly. I tested this patch for freescale powerpc platforms. But It may needs be taken care by all architecture like ARM, powerpc. If this is the case; this flag should be in top level Makefile (not sure)
I suspect a top-level option would be best, perhaps near this one in Makefile:
KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
I also agree with Scott and Simon, default, top level, using cc-option just like the Linux kernel please, thanks!