[OpenBIOS] static and global variable problem

[Programmingkid]

On Dec 21, 2012, at 8:09 AM, Alexander Graf wrote:

> 
> On 21.12.2012, at 10:55, Mark Cave-Ayland wrote:
> 
>> On 20/12/12 20:16, Programmingkid wrote:
>> 
>>> I was doing some debugging of an issue with the hash_page_32() function in the file ofmem.c, when I noticed a very odd problem. The static variable next_grab_slot never changes value. I tried declaring it as a global variable and its value still never changes. I used gdb to monitor its value. Local variables work just fine. Any body know a way to fix this problem? My guess is this is a gcc problem. What is your theory?
>> 
>> The first thing I would check is have you changed the CFLAGS from -Os to -O0 to disable optimisation? Otherwise gdb is missing information it needs to work correctly, and will start to do some strange things.
>> 
>> Also I note that when Alex did some work on this back in 2009, he made a minor change to PPC's OFMEM here: http://lists.openbios.org/pipermail/openbios/2009-July/003796.html. Alex - should the change to hash_page_32() be committed or is that another hack to work around something else?
> 
> I quite frankly don't remember what exactly I was trying to fix. I think the basic idea was that incrementing it by 3 we evict entries more fairly. But thinking about it again, I don't seem to understand why either myself :)

I was investigating this problem and was wondering if register r31 has any special purpose in OpenBIOS. My guess is it is suppose to point to the global variable address space.