Re: 2.6.23-rc3-mm1

[Andi Kleen]

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?

> 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

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