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
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