From 72c0ebbea413a3d05847a849d629082e5408232e Mon Sep 17 00:00:00 2001
From: isle2983 <isle2983@yahoo.com>
Date: Sun, 29 Jan 2017 14:38:21 -0700
Subject: [PATCH 1/2] Example 1 - avoid optimizing out stack variable clearing
 by using an __attribute__

---
 src/ecmult_gen_impl.h | 2 +-
 src/group_impl.h      | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/ecmult_gen_impl.h b/src/ecmult_gen_impl.h
index 35f2546077..4ab9c391a7 100644
--- a/src/ecmult_gen_impl.h
+++ b/src/ecmult_gen_impl.h
@@ -150,7 +150,7 @@ static void secp256k1_ecmult_gen(const secp256k1_ecmult_gen_context *ctx, secp25
         secp256k1_ge_from_storage(&add, &adds);
         secp256k1_gej_add_ge(r, r, &add);
     }
-    bits = 0;
+    secp256k1_int_clear(&bits);
     secp256k1_ge_clear(&add);
     secp256k1_scalar_clear(&gnb);
 }
diff --git a/src/group_impl.h b/src/group_impl.h
index 7d723532ff..ab1c98f342 100644
--- a/src/group_impl.h
+++ b/src/group_impl.h
@@ -7,6 +7,7 @@
 #ifndef _SECP256K1_GROUP_IMPL_H_
 #define _SECP256K1_GROUP_IMPL_H_
 
+#include <string.h>
 #include "num.h"
 #include "field.h"
 #include "group.h"
@@ -213,6 +214,14 @@ static void secp256k1_ge_clear(secp256k1_ge *r) {
     secp256k1_fe_clear(&r->y);
 }
 
+static void __attribute__((optimize("O0"))) secp256k1_secure_clear(void *s, size_t n) {
+    (void) memset(s, 0, n);
+}
+
+static void secp256k1_int_clear(int *r) {
+    secp256k1_secure_clear(r, sizeof(*r));
+}
+
 static int secp256k1_ge_set_xquad(secp256k1_ge *r, const secp256k1_fe *x) {
     secp256k1_fe x2, x3, c;
     r->x = *x;

From cdd46814c4abcd7bc9ce73d616347964ac7ac9be Mon Sep 17 00:00:00 2001
From: isle2983 <isle2983@yahoo.com>
Date: Sun, 29 Jan 2017 14:39:58 -0700
Subject: [PATCH 2/2] Example 2 - avoid optimizing out stack variable clearing
 by using the 'volatile' keyword

---
 src/group_impl.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/group_impl.h b/src/group_impl.h
index ab1c98f342..a4d3ddf257 100644
--- a/src/group_impl.h
+++ b/src/group_impl.h
@@ -214,8 +214,13 @@ static void secp256k1_ge_clear(secp256k1_ge *r) {
     secp256k1_fe_clear(&r->y);
 }
 
-static void __attribute__((optimize("O0"))) secp256k1_secure_clear(void *s, size_t n) {
-    (void) memset(s, 0, n);
+typedef void *(*memset_t)(void *, int, size_t);
+
+static volatile memset_t secure_memset = memset;
+
+static void secp256k1_secure_clear(void *s, size_t n) {
+    (void) secure_memset(s, 0, n);
+
 }
 
 static void secp256k1_int_clear(int *r) {