[coreboot] Makefiles question: -fno-delete-null-pointer-checks needed in Makefiles

Martin Roth martin.roth at se-eng.com
Thu Mar 7 03:35:19 CET 2013

On 03/06/2013 09:29 AM, Jens Rottmann wrote:
> Hi Martin (and all),
> I wrote:
>>> You dereference dev in line 132, so if it's really 0,
>>> will you then ever reach this check?? (I don't know if
>>> in romstage *NULL is caught.)
> You wrote:
>> yes, if it's 0, we still reach the code. I've changed it
>> to not dereference it before checking it though.
> Per default, after any *ptr, GCC assumes a SEGFAULT would occur if ptr was ==0, so if control flow does reach the following code ptr must be !=0. ==> After any *ptr GCC will optimize away all ptr==0 or !=0 checks.  I know that because I recently hunted a related bug for a week (U-Boot, ARM, different project) until I looked at the actual assembly code.
> Are you sure romstage (or maybe even ramstage?) will *NULL without segfaulting and just continue? And is romstage compiled with GCC (+ CAR) or is romcc used?
> In that case "-fno-delete-null-pointer-checks" must be added to the GCC options.
> http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
> I greped a bit, looks like it's not in any Makefiles yet.
> Could someone who knows Coreboot's make/build system better than me maybe help, please?
> Thanks
> Jens
   I'm pretty sure, but I'm not *COMPLETELY* positive about this.  I had 
to add this check because I kept getting null pointers due to an issue 
with the unterminated #pragma pack(1)  in the porting.h file - that was 
messing my pointers up pretty badly.  I'll work on checking this issue 
directly and respond back with what I find out.

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