From 5d2610c96d0611a28260dbf9f9481cd39aa463dc Mon Sep 17 00:00:00 2001
From: Daniel Pouzzner <douzzer@wolfssl.com>
Date: Sun, 11 Sep 2022 13:23:53 -0500
Subject: [PATCH] wolfssl/wolfcrypt/sp_int.h and wolfcrypt/src/sp_int.c: add
 struct sp_int_minimal, with same structure as struct sp_int but only one
 digit, to allow error-free access to sp_ints allocated with ALLOC_SP_INT()
 with fewer than SP_INT_DIGITS digits, and use the new type in _sp_zero() and
 sp_init_size() to eliminate -Werror=array-bounds on _sp_zero() under gcc-13.

---
 wolfcrypt/src/sp_int.c     | 20 +++++++++++++++-----
 wolfssl/wolfcrypt/sp_int.h | 13 +++++++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/wolfcrypt/src/sp_int.c b/wolfcrypt/src/sp_int.c
index cb78a7681..c7973d989 100644
--- a/wolfcrypt/src/sp_int.c
+++ b/wolfcrypt/src/sp_int.c
@@ -4352,10 +4352,10 @@ static int _sp_mont_red(sp_int* a, sp_int* m, sp_int_digit mp);
  */
 static void _sp_zero(sp_int* a)
 {
-    a->used = 0;
-    a->dp[0] = 0;
+    ((sp_int_minimal *)a)->used = 0;
+    ((sp_int_minimal *)a)->dp[0] = 0;
 #ifdef WOLFSSL_SP_INT_NEGATIVE
-    a->sign = MP_ZPOS;
+    ((sp_int_minimal *)a)->sign = MP_ZPOS;
 #endif
 }
 
@@ -4394,10 +4394,20 @@ int sp_init(sp_int* a)
  */
 int sp_init_size(sp_int* a, int size)
 {
-    int err = sp_init(a);
+    int err = MP_OKAY;
+
+    if (a == NULL) {
+        err = MP_VAL;
+    }
+    if (err == MP_OKAY) {
+    #ifdef HAVE_WOLF_BIGINT
+        wc_bigint_init(&a->raw);
+    #endif
+        _sp_zero(a);
+    }
 
     if (err == MP_OKAY) {
-        a->size = size;
+        ((sp_int_minimal *)a)->size = size;
     }
 
     return err;
diff --git a/wolfssl/wolfcrypt/sp_int.h b/wolfssl/wolfcrypt/sp_int.h
index ca91b52e1..7d5de0674 100644
--- a/wolfssl/wolfcrypt/sp_int.h
+++ b/wolfssl/wolfcrypt/sp_int.h
@@ -778,6 +778,19 @@ typedef struct sp_int {
     sp_int_digit dp[SP_INT_DIGITS];
 } sp_int;
 
+typedef struct sp_int_minimal {
+    int used;
+    int size;
+#ifdef WOLFSSL_SP_INT_NEGATIVE
+    int sign;
+#endif
+#ifdef HAVE_WOLF_BIGINT
+    struct WC_BIGINT raw;
+#endif
+    /** First digit of number.  */
+    sp_int_digit dp[1];
+} sp_int_minimal;
+
 /* Multi-precision integer type is SP integer type. */
 typedef sp_int       mp_int;
 /* Multi-precision integer digit type is SP integer digit type.