[PATCH] Mark nonstring use cases with __nonstring__ attribute.

diff --git a/cipher/chacha20.c b/cipher/chacha20.c
index 8b547db3..848adbe5 100644
--- a/cipher/chacha20.c
+++ b/cipher/chacha20.c
@@ -428,8 +428,8 @@ static void
 chacha20_keysetup (CHACHA20_context_t *ctx, const byte *key,
                    unsigned int keylen)
 {
-  static const char sigma[16] = "expand 32-byte k";
-  static const char tau[16] = "expand 16-byte k";
+  static const char sigma[16] _GCRY_GCC_ATTR_NONSTRING = "expand 32-byte k";
+  static const char tau[16] _GCRY_GCC_ATTR_NONSTRING = "expand 16-byte k";
   const char *constants;
 
   ctx->input[4] = buf_get_le32(key + 0);
diff --git a/cipher/cipher-gcm-siv.c b/cipher/cipher-gcm-siv.c
index 1f7a52bc..b92ae45d 100644
--- a/cipher/cipher-gcm-siv.c
+++ b/cipher/cipher-gcm-siv.c
@@ -248,22 +248,22 @@ do_ctr_le32 (gcry_cipher_hd_t c, byte *outbuf, const byte *inbuf,
 static int
 gcm_siv_selftest (gcry_cipher_hd_t c)
 {
-  static const byte in1[GCRY_SIV_BLOCK_LEN] =
+  static const byte in1[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
-  static const byte out1[GCRY_SIV_BLOCK_LEN] =
+  static const byte out1[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
-  static const byte in2[GCRY_SIV_BLOCK_LEN] =
+  static const byte in2[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\x9c\x98\xc0\x4d\xf9\x38\x7d\xed\x82\x81\x75\xa9\x2b\xa6\x52\xd8";
-  static const byte out2[GCRY_SIV_BLOCK_LEN] =
+  static const byte out2[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\x4e\x4c\x60\x26\xfc\x9c\x3e\xf6\xc1\x40\xba\xd4\x95\xd3\x29\x6c";
-  static const byte polyval_key[GCRY_SIV_BLOCK_LEN] =
+  static const byte polyval_key[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\x25\x62\x93\x47\x58\x92\x42\x76\x1d\x31\xf8\x26\xba\x4b\x75\x7b";
-  static const byte ghash_key[GCRY_SIV_BLOCK_LEN] =
+  static const byte ghash_key[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\xdc\xba\xa5\xdd\x13\x7c\x18\x8e\xbb\x21\x49\x2c\x23\xc9\xb1\x12";
-  static const byte polyval_data[GCRY_SIV_BLOCK_LEN * 2] =
+  static const byte polyval_data[GCRY_SIV_BLOCK_LEN * 2] _GCRY_GCC_ATTR_NONSTRING =
       "\x4f\x4f\x95\x66\x8c\x83\xdf\xb6\x40\x17\x62\xbb\x2d\x01\xa2\x62"
       "\xd1\xa2\x4d\xdd\x27\x21\xd0\x06\xbb\xe4\x5f\x20\xd3\xc9\xf3\x62";
-  static const byte polyval_tag[GCRY_SIV_BLOCK_LEN] =
+  static const byte polyval_tag[GCRY_SIV_BLOCK_LEN] _GCRY_GCC_ATTR_NONSTRING =
       "\xf7\xa3\xb4\x7b\x84\x61\x19\xfa\xe5\xb7\x86\x6c\xf5\xe5\xb7\x7e";
   byte tmp[GCRY_SIV_BLOCK_LEN];
 
diff --git a/cipher/ecc.c b/cipher/ecc.c
index d9cd32c3..51364b64 100644
--- a/cipher/ecc.c
+++ b/cipher/ecc.c
@@ -1699,7 +1699,7 @@ static gpg_err_code_t
 compute_keygrip (gcry_md_hd_t md, gcry_sexp_t keyparms)
 {
 #define N_COMPONENTS 6
-  static const char names[N_COMPONENTS] = "pabgnq";
+  static const char names[N_COMPONENTS] _GCRY_GCC_ATTR_NONSTRING = "pabgnq";
   gpg_err_code_t rc;
   gcry_sexp_t l1;
   gcry_mpi_t values[N_COMPONENTS];
diff --git a/cipher/serpent.c b/cipher/serpent.c
index 74d132ab..72a2287d 100644
--- a/cipher/serpent.c
+++ b/cipher/serpent.c
@@ -1880,9 +1880,9 @@ serpent_test (void)
   static struct test
   {
     int key_length;
-    unsigned char key[32];
-    unsigned char text_plain[16];
-    unsigned char text_cipher[16];
+    unsigned char key[32] _GCRY_GCC_ATTR_NONSTRING;
+    unsigned char text_plain[16] _GCRY_GCC_ATTR_NONSTRING;
+    unsigned char text_cipher[16] _GCRY_GCC_ATTR_NONSTRING;
   } test_data[] =
     {
       {
diff --git a/src/gcrypt.h.in b/src/gcrypt.h.in
index a9c36aa6..aa8a1f37 100644
--- a/src/gcrypt.h.in
+++ b/src/gcrypt.h.in
@@ -96,6 +96,12 @@ extern "C" {
 #define _GCRY_GCC_ATTR_SENTINEL(a) __attribute__ ((sentinel(a)))
 #endif
 
+#if _GCRY_GCC_VERSION >= 80000
+#define _GCRY_GCC_ATTR_NONSTRING __attribute__((__nonstring__))
+#else
+#define _GCRY_GCC_ATTR_NONSTRING
+#endif
+
 #endif /*__GNUC__*/
 
 #ifndef _GCRY_GCC_ATTR_DEPRECATED
@@ -113,6 +119,9 @@ extern "C" {
 #ifndef _GCRY_GCC_ATTR_SENTINEL
 #define _GCRY_GCC_ATTR_SENTINEL(a)
 #endif
+#ifndef _GCRY_GCC_ATTR_NONSTRING
+#define _GCRY_GCC_ATTR_NONSTRING
+#endif
 
 /* Make up an attribute to mark functions and types as deprecated but
    allow internal use by Libgcrypt.  */
diff --git a/tests/basic.c b/tests/basic.c
index 72c65b58..b62a9a90 100644
--- a/tests/basic.c
+++ b/tests/basic.c
@@ -589,7 +589,7 @@ check_cbc_mac_cipher (void)
 static void
 check_aes128_cbc_cts_cipher (void)
 {
-  static const char key[128 / 8] = "chicken teriyaki";
+  static const char key[128 / 8] _GCRY_GCC_ATTR_NONSTRING = "chicken teriyaki";
   static const unsigned char plaintext[] =
     "I would like the General Gau's Chicken, please, and wonton soup.";
   static const struct tv
@@ -3550,15 +3550,15 @@ _check_gcm_cipher (unsigned int step)
   static const struct tv
   {
     int algo;
-    char key[MAX_DATA_LEN];
-    char iv[MAX_DATA_LEN];
+    char key[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
+    char iv[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
     int ivlen;
-    unsigned char aad[MAX_DATA_LEN];
+    unsigned char aad[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
     int aadlen;
-    unsigned char plaintext[MAX_GCM_DATA_LEN];
+    unsigned char plaintext[MAX_GCM_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
     int inlen;
-    char out[MAX_GCM_DATA_LEN];
-    char tag[MAX_DATA_LEN];
+    char out[MAX_GCM_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
+    char tag[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
     int taglen;
     int should_fail;
   } tv[] =
@@ -5743,14 +5743,14 @@ check_gcm_siv_cipher (void)
   {
     int algo;
     int flags;
-    char key[MAX_DATA_LEN];
-    char nonce[12];
-    char ad[MAX_DATA_LEN];
+    char key[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
+    char nonce[12] _GCRY_GCC_ATTR_NONSTRING;
+    char ad[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
     int adlen;
-    unsigned char plaintext[MAX_DATA_LEN * 2];
+    unsigned char plaintext[MAX_DATA_LEN * 2] _GCRY_GCC_ATTR_NONSTRING;
     int inlen;
-    char out[MAX_DATA_LEN * 2];
-    char tag[MAX_DATA_LEN];
+    char out[MAX_DATA_LEN * 2] _GCRY_GCC_ATTR_NONSTRING;
+    char tag[MAX_DATA_LEN] _GCRY_GCC_ATTR_NONSTRING;
   } tv[] =
     {
       /* Test vectors from RFC8452 */
@@ -9059,10 +9059,10 @@ static void
 check_ocb_cipher_largebuf_split (int algo, int keylen, const char *tagexpect,
 				 unsigned int splitpos)
 {
-  static const unsigned char key[32] =
+  static const unsigned char key[32] _GCRY_GCC_ATTR_NONSTRING =
         "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F"
         "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F";
-  static const unsigned char nonce[12] =
+  static const unsigned char nonce[12] _GCRY_GCC_ATTR_NONSTRING =
         "\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F\x00\x01\x02\x03";
   const size_t buflen = 1024 * 1024 * 2 + 32;
   unsigned char *inbuf;
@@ -9282,10 +9282,10 @@ out_free:
 static void
 check_ocb_cipher_checksum (int algo, int keylen)
 {
-  static const unsigned char key[32] =
+  static const unsigned char key[32] _GCRY_GCC_ATTR_NONSTRING =
 	"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F"
 	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F";
-  static const unsigned char nonce[12] =
+  static const unsigned char nonce[12] _GCRY_GCC_ATTR_NONSTRING =
 	"\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F\x00\x01\x02\x03";
   const size_t buflen = 128 * 16;
   unsigned char *inbuf, *outbuf;
diff --git a/tests/keygrip.c b/tests/keygrip.c
index cf650350..503a2c05 100644
--- a/tests/keygrip.c
+++ b/tests/keygrip.c
@@ -56,7 +56,7 @@ static struct
 {
   int algo;
   const char *key;
-  const unsigned char grip[20];
+  const unsigned char grip[20] _GCRY_GCC_ATTR_NONSTRING;
   int skip_when_fips;
 } key_grips[] =
   {