Re: 2.6.23-rc3-mm1

[Randy Dunlap]

On Wed, 22 Aug 2007 21:38:58 +0200 Andi Kleen wrote:

> On Wed, Aug 22, 2007 at 11:32:11AM -0700, Andrew Morton wrote:
> > > On Wed, 22 Aug 2007 02:06:48 -0700 Andrew Morton wrote:
> > > 
> > > > 
> > > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc3/2.6.23-rc3-mm1/
> > > 
> > > allyesconfig on x86_64 says:
> > > 
> > > kernel/unwind.c:1016:31: error: undefined identifier '__builtin_labs'
> > > kernel/unwind.c:1232:25: error: undefined identifier '__builtin_labs'
> > > 
> > 
> 
> Why does that compiler not know __builtin_abs?

I dunno:

> gcc --version
gcc (GCC) 4.1.0 (SUSE Linux)


> > One wonders why x86_64-mm-unwinder.patch has an open-coded call to
> > __builtin_labs(), when include/linux/kernel.h:abs() should do a fine job.
> 
> I'll fix.
> 
> > 
> > And what's this stuff, anyway?
> > 
> > +typedef unsigned long uleb128_t;
> > +typedef   signed long sleb128_t;
> > +#define sleb128abs __builtin_labs
> > 
> > unsigned and signed little-endian 128-bit types?  Nope, they're 32-bit or
> > 64-bit.   All very mysterious.
> 
> dwarf2 uses a magic compressing encoding for numbers that uses less bytes
> for small numbers and more bytes for larger numbers. These are the base
> types for this.
> 
> It's similar to fs/reiser4/dscale.h in your tree.
> 
> -Andi

---
~Randy
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