Abstract out verify logic for fe_clear

Author: sipa

src/field.h

@@ -81,6 +81,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
 #  define secp256k1_fe_normalizes_to_zero secp256k1_fe_impl_normalizes_to_zero
 #  define secp256k1_fe_normalizes_to_zero_var secp256k1_fe_impl_normalizes_to_zero_var
 #  define secp256k1_fe_set_int secp256k1_fe_impl_set_int
+#  define secp256k1_fe_clear secp256k1_fe_impl_clear
 #endif /* !defined(VERIFY) */
 
 /** Normalize a field element.
@@ -123,7 +124,11 @@ static int secp256k1_fe_normalizes_to_zero_var(const secp256k1_fe *r);
  */
 static void secp256k1_fe_set_int(secp256k1_fe *r, int a);
 
-/** Sets a field element equal to zero, initializing all fields. */
+/** Set a field element to 0.
+ *
+ * On input, a does not need to be initialized.
+ * On output, a represents 0, is normalized and has magnitude 0.
+ */
 static void secp256k1_fe_clear(secp256k1_fe *a);
 
 /** Verify whether a field element is zero. Requires the input to be normalized. */

src/field_10x26_impl.h

@@ -286,12 +286,8 @@ SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
     return a->n[0] & 1;
 }
 
-SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe *a) {
+SECP256K1_INLINE static void secp256k1_fe_impl_clear(secp256k1_fe *a) {
     int i;
-#ifdef VERIFY
-    a->magnitude = 0;
-    a->normalized = 1;
-#endif
     for (i=0; i<10; i++) {
         a->n[i] = 0;
     }

src/field_5x52_impl.h

@@ -232,12 +232,8 @@ SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
     return a->n[0] & 1;
 }
 
-SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe *a) {
+SECP256K1_INLINE static void secp256k1_fe_impl_clear(secp256k1_fe *a) {
     int i;
-#ifdef VERIFY
-    a->magnitude = 0;
-    a->normalized = 1;
-#endif
     for (i=0; i<5; i++) {
         a->n[i] = 0;
     }

src/field_impl.h

@@ -194,6 +194,14 @@ SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe *r, int a) {
     r->normalized = 1;
     secp256k1_fe_verify(r);
 }
+
+static void secp256k1_fe_impl_clear(secp256k1_fe *a);
+SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe *a) {
+    a->magnitude = 0;
+    a->normalized = 1;
+    secp256k1_fe_impl_clear(a);
+    secp256k1_fe_verify(a);
+}
 #endif /* defined(VERIFY) */
 
 #endif /* SECP256K1_FIELD_IMPL_H */