[PATCH 1/2] Support clang for explicit_bzero

[roucaries . bastien]

From: Bastien Roucariès <rouca@debian.org>

According to https://bugs.llvm.org/show_bug.cgi?id=15495#c11
llvm need g type constraint

Signed-off-by: Bastien Roucariès <rouca@debian.org>
---
 lib/explicit_bzero.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/explicit_bzero.c b/lib/explicit_bzero.c
index 87fadba81a..71a1cca3b0 100644
--- a/lib/explicit_bzero.c
+++ b/lib/explicit_bzero.c
@@ -56,9 +56,19 @@ explicit_bzero (void *s, size_t len)
   (void) memset_s (s, len, '\0', len);
 #else
   memset (s, '\0', len);
-# if defined __GNUC__ && !defined __clang__
-  /* Compiler barrier.  */
+# if defined __GNUC__
+/* Compiler barrier.  */
+#  if !defined __clang__
   asm volatile ("" ::: "memory");
+#  else
+   /* See https://bugs.llvm.org/show_bug.cgi?id=15495#c11
+      with asm("" ::: "memory") LLVM analyzes uses of 's'
+      and finds that the whole thing is dead and eliminates it.
+
+      Using g workarround this problem
+   */
+  __asm__ volatile("" : : "g"(s) : "memory");
+#  endif
 # endif
 #endif
 }
-- 
2.29.2