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

[Roman Zippel <zippel@linux-m68k.org>]

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.)

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.

bye, Roman
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