On Fri, 2020-08-14 at 19:09 -0700, Nick Desaulniers wrote: > LLVM implemented a recent "libcall optimization" that lowers calls to > `sprintf(dest, "%s", str)` where the return value is used to > `stpcpy(dest, str) - dest`. This generally avoids the machinery involved > in parsing format strings. Calling `sprintf` with overlapping arguments > was clarified in ISO C99 and POSIX.1-2001 to be undefined behavior. > > `stpcpy` is just like `strcpy` except it returns the pointer to the new > tail of `dest`. This allows you to chain multiple calls to `stpcpy` in > one statement. [] > diff --git a/include/linux/string.h b/include/linux/string.h [] > @@ -31,6 +31,9 @@ size_t strlcpy(char *, const char *, size_t); > #ifndef __HAVE_ARCH_STRSCPY > ssize_t strscpy(char *, const char *, size_t); > #endif > +#ifndef __HAVE_ARCH_STPCPY > +extern char *stpcpy(char *__restrict__, const char *__restrict__); If __restrict__ is used, perhaps it should follow the kernel style used by attributes like __iomem and __user extern char *stpcpy(char __restrict *dest, const char __restrict *src); (though I would lose the extern too) char *stpcpy(char __restrict *dest, const char __restrict *src);
