Re: Cleanup possibility in asm-i386/string.h

[Andi Kleen <ak@suse.de>]

On Tuesday 07 February 2006 13:00, Roman Zippel wrote:
> Hi,
> 
> On Tue, 7 Feb 2006, Andi Kleen wrote:
> 
> > If you feel the need to remove some more code: Now that gcc 2.95 isn't supported
> > anymore there isn't really a need to keep the handwritten inline string functions
> > in asm-i386/string.h around. Just declaring them as normal externs will cause
> > gcc to use its builtin expansions, which are typically better than these old inline
> > functions with inline assembly.
> > 
> > For out of line the C versions in lib/string.c can be used (by not setting __ARCH_*) 
> > x86-64 did it like this forever and I guess it would be valuable cleanup for i386 too.
> 
> The only problem is that we compile with -ffreestanding which implies 
> -fno-builtin, so just declaring them as normal externs is not enough and 
> you have to something like this:
> 
> #define __HAVE_ARCH_MEMSET
> extern void *memset(void *, int, __kernel_size_t);
> #define memset(d, c, n) __builtin_memset(d, c, n)
> 
> (BTW you do this already in x86-64.)

Yes thinking about it the x86-64 string.h could just be copied over to i386.
It should already do everything correctly and I don't think there is 
anything really 64bit specific in there.

> Another problem here is because of -fno-builtin it's not easy to use the 
> generic functions as fallback. x86-64 basically does this: 
> 
> #define strlen __builtin_strlen
> size_t strlen(const char * s);
> 
> #ifndef __HAVE_ARCH_STRLEN
> extern __kernel_size_t strlen(const char *);
> #endif
> 
> This means you define a prototype for the builtin function and not for the 
> normal function. I'm not sure this is really intended.

What good would be a prototype for a symbol that is defined to a different symbol?

-Andi