addressed Copilot review comments

Author: miyazakh

doc/dox_comments/header_files/signature.h

@@ -11,13 +11,12 @@
     \param sig_type A signature type enum value such as
     WC_SIGNATURE_TYPE_ECC or WC_SIGNATURE_TYPE_RSA.
     \param key Pointer to the key structure corresponding to sig_type:
-    pass an ecc_key* (cast to const void*) for
-    WC_SIGNATURE_TYPE_ECC, or a RsaKey* for
+    pass an ecc_key* for WC_SIGNATURE_TYPE_ECC, or a RsaKey* for
     WC_SIGNATURE_TYPE_RSA / WC_SIGNATURE_TYPE_RSA_W_ENC.
     The caller is responsible for ensuring the pointer refers to the correct
     type; this function cannot verify the actual runtime type of the object.
-    \param key_len Must be exactly sizeof(ecc_key) or
-    sizeof(RsaKey) matching the sig_type. Passing any other value
+    \param key_len If key is non-NULL, key_len Must be exactly sizeof(ecc_key)
+    or sizeof(RsaKey) matching the sig_type. Passing any other value
     causes the function to return BAD_FUNC_ARG without dereferencing key.
     The conventional idiom is to pass sizeof(*key) at the call site.
 

wolfcrypt/src/signature.c

@@ -94,9 +94,10 @@ int wc_SignatureGetSize(enum wc_SignatureType sig_type,
         case WC_SIGNATURE_TYPE_ECC:
 #ifdef HAVE_ECC
             /* Verify that key_len matches exactly sizeof(ecc_key).
-             * This is a necessary but not sufficient type check: the void*
-             * API cannot verify the actual runtime type of the pointed-to
-             * object.  Callers must pass a valid ecc_key* cast to void*. */
+             * This is a necessary but not sufficient type check:
+             * the const void* API cannot verify the actual runtime
+             * type of the pointed-to object.
+             * Callers must pass a valid ecc_key* cast to const void*. */
             if (key_len == sizeof(ecc_key)) {
 #if defined(HAVE_SELFTEST) || (defined(HAVE_FIPS) && FIPS_VERSION3_LT(5,0,0))
                 sig_len = wc_ecc_sig_size((ecc_key*)(wc_ptr_t)key);