On Wed, 2018-08-22 at 13:00 +0200, Rasmus Villemoes wrote: > This wraps strchr and friends in macros that ensure the return value has > type const char* if the passed-in string (which the return value points > into) also has type const char*. The (s)+0 thing is to force a const > char[] (e.g. a string literal) to decay to a const char* for the > __same_type comparison. [] > diff --git a/include/linux/string.h b/include/linux/string.h [] > +#define strchr(s, c) ( \ > + __builtin_choose_expr(__same_type((s) + 0, const char *), \ > + (const char *)strchr(s, c), \ > + strchr(s, c))) > +#endif [] > diff --git a/lib/string.c b/lib/string.c [] > @@ -367,7 +367,7 @@ EXPORT_SYMBOL(strncmp); > * @s: The string to be searched > * @c: The character to search for > */ > -char *strchr(const char *s, int c) > +char *(strchr)(const char *s, int c) I've tried to use this macro/function wrapping a few times before, but it seems that it's fairly unusual in the kernel. I believe there may not be any current uses of that style. A comment explaining the form might be useful.
