Yes true sorry :-|. Kind regards. On Tue, 26 Jun 2018 at 21:43, Rich Felker wrote: > On Fri, Jun 15, 2018 at 01:37:43PM +0000, David CARLIER wrote: > > Hi dear lists, > > this is my first message so forgive me if this idea had already been > rejected. > > It's definitely not rejected outright, and I think the consensus is > to adopt it. But.. > > > From c0a16cf96b96b009097d6ed656a2a7b8969e8399 Mon Sep 17 00:00:00 2001 > > From: David Carlier > > Date: Fri, 15 Jun 2018 13:30:09 +0000 > > Subject: [PATCH] string: adding simple explicit_bzero implementation. > > > > glibc implementing it and modern security based code starting > > using it widely, here a simple implementation using memory barrier. > > --- > > include/string.h | 1 + > > src/string/explicit_bzero.c | 8 ++++++++ > > 2 files changed, 9 insertions(+) > > create mode 100644 src/string/explicit_bzero.c > > > > diff --git a/include/string.h b/include/string.h > > index ce1dc300..795a2abc 100644 > > --- a/include/string.h > > +++ b/include/string.h > > @@ -82,6 +82,7 @@ void *memccpy (void *__restrict, const void > *__restrict, int, size_t); > > char *strsep(char **, const char *); > > size_t strlcat (char *, const char *, size_t); > > size_t strlcpy (char *, const char *, size_t); > > +void explicit_bzero (void *, size_t); > > #endif > > > > #ifdef _GNU_SOURCE > > diff --git a/src/string/explicit_bzero.c b/src/string/explicit_bzero.c > > new file mode 100644 > > index 00000000..47dba3c7 > > --- /dev/null > > +++ b/src/string/explicit_bzero.c > > @@ -0,0 +1,8 @@ > > +#define _BSD_SOURCE > > +#include > > + > > +void explicit_bzero(void *d, size_t n) > > +{ > > + memset(d, 0, n); > > + __asm__ volatile("": "r="(d) :: "memory"); > > +} > > -- > > The constraint here looks wrong. Normally = is written before the > type, not after; I'm not sure if all compiler versions accept the > unusual form with it after. But more importantly you have it as an > output constraint, where it's essentially a dead store, such that the > asm block does nothing to make explicit_bzero force the memset to > happen. > > I think you meant for the constraint to be an input constraint "r"(d). > Does that sound right? > > Rich >