[parisc-linux] Re: Looking at vfprintf.c and alloca.

["Michael S. Zick" <mszick@morethan.org>]

On Tue July 18 2006 14:30, Carlos O'Donell wrote:
> On 7/18/06, Randolph Chung <randolph@tausq.org> wrote:
> > I tried this with both old (gcc-3.[34]) and new gcc (gcc-4.[01]) and i
> > don't think this works....
> >
> > tausq@riot:~$ gcc-4.1 -Wall -o alloca alloca.c; ./alloca
> > ptr = 0xc04ca590
> > old = 0xc04ca3d0
> > &old[100] = 0xc04ca560
> 
> I thought so, if this code is ever execute it will be wrong.
>

I did not look at the original code - just the posted example.

If the library code is depending on an expected difference between
the old and new stack position (other than direction) 
- it will be in trouble.

> 
> I think our tst-printfsz failure is related to this code trying to
> expand the specs and getting the wrong answer.
> 
> Michael, want to write a patch to fix this for glibc? :)
> I'll support you on libc-alpha!
> 

It just so happened that I was compiling glibc and during this exchange
vfprintf.c scrolled by...
I think it set some sort of record for "number of warning messages"

So it needs work.  Probably would be better to give someone else a chance.

Getting -finstrument-functions and the related __builtin_{frame,return}_address()
to work is taking all of my time right now.

> In glibc I don't think the code should be a runtime check at all,
> there are STACK_GROWS_UP macros that should be used.
> 

Sounds reasonable to me.

> c.
Mike
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