Use strlen when searching for a nul char
Commit Message
Mike Frysinger wrote:
> the issue isn't what version of gcc is used to build glibc. this is an
> installed header, and we made guarantees that the installed headers work
> with much older versions of gcc at runtime. those guarantees don't hard
> extend to pure-optimizations, but typically we wait much longer for those
> versions to cycle out of common use. dropping code that requires gcc7
> (which doesn't even exist yet) doesn't fall into that bucket.
OK, here is the patch with the old define left in:
Comments
On 20 Apr 2016 14:50, Wilco Dijkstra wrote:
> #ifndef _HAVE_STRING_ARCH_strchr
> extern void *__rawmemchr (const void *__s, int __c);
> -# define strchr(s, c) \
> +# define strchr(s, c) \
> (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s) \
> && (c) == '\0' \
> ? (char *) __rawmemchr (s, c) \
> : __builtin_strchr (s, c)))
> #endif
>
> +#ifndef _HAVE_STRING_ARCH_rawmemchr
> +extern void *__rawmemchr (const void *__s, int __c);
> +# define __rawmemchr(s, c) \
> + (__extension__ ({ char *__s = (char *)(s); \
> + __builtin_constant_p (c) && (c) == '\0' \
> + ? (void *)(__s + strlen (__s)) \
> + : __rawmemchr (__s, (c));}))
> +# ifdef __USE_GNU
> +# define rawmemchr(s,c) __rawmemchr ((s), (c))
> +# endif
> +#endif
this relies on _HAVE_STRING_ARCH_strchr & _HAVE_STRING_ARCH_rawmemchr
being in sync in order for the strchr->strlen rewrite. should we just
do the strlen change in strchr itself too ?
-mike
Mike Frysinger wrote:
> this relies on _HAVE_STRING_ARCH_strchr & _HAVE_STRING_ARCH_rawmemchr
> being in sync in order for the strchr->strlen rewrite. should we just
> do the strlen change in strchr itself too ?
If a target only defines _HAVE_STRING_ARCH_rawmemchr then presumably
it supports a fast rawmemchr, so it might be expected that strchr defers to rawmemchr
as it does today rather than using strlen.
If a target only defines _HAVE_STRING_ARCH_strchr then rawmemchr
would still use strlen, which is fine.
Wilco
> #ifndef _HAVE_STRING_ARCH_strchr
> extern void *__rawmemchr (const void *__s, int __c);
> -# define strchr(s, c) \
> +# define strchr(s, c) \
> (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s) \
> && (c) == '\0' \
> ? (char *) __rawmemchr (s, c) \
> : __builtin_strchr (s, c)))
> #endif
>
> +#ifndef _HAVE_STRING_ARCH_rawmemchr
> +extern void *__rawmemchr (const void *__s, int __c);
> +# define __rawmemchr(s, c) \
> + (__extension__ ({ char *__s = (char *)(s); \
> + __builtin_constant_p (c) && (c) == '\0' \
> + ? (void *)(__s + strlen (__s)) \
> + : __rawmemchr (__s, (c));}))
> +# ifdef __USE_GNU
> +# define rawmemchr(s,c) __rawmemchr ((s), (c))
> +# endif
> +#endif
@@ -60,13 +60,25 @@
#ifndef _HAVE_STRING_ARCH_strchr
extern void *__rawmemchr (const void *__s, int __c);
-# define strchr(s, c) \
+# define strchr(s, c) \
(__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s) \
&& (c) == '\0' \
? (char *) __rawmemchr (s, c) \
: __builtin_strchr (s, c)))
#endif
+#ifndef _HAVE_STRING_ARCH_rawmemchr
+extern void *__rawmemchr (const void *__s, int __c);
+# define __rawmemchr(s, c) \
+ (__extension__ ({ char *__s = (char *)(s); \
+ __builtin_constant_p (c) && (c) == '\0' \
+ ? (void *)(__s + strlen (__s)) \
+ : __rawmemchr (__s, (c));}))
+# ifdef __USE_GNU
+# define rawmemchr(s,c) __rawmemchr ((s), (c))
+# endif
+#endif
+
/* Copy SRC to DEST, returning pointer to final NUL byte. */
#ifdef __USE_GNU