rpc: annotate functions returning error codes to ensure they are checked

diff --git a/main/process/get_master_blinding_key.c b/main/process/get_master_blinding_key.c
index 4a46252..fb59630 100644
--- a/main/process/get_master_blinding_key.c
+++ b/main/process/get_master_blinding_key.c
@@ -20,16 +20,17 @@ void get_master_blinding_key_process(void* process_ptr)
     if (keychain_get_confirm_export_blinding_key()) {
         // Optional field to suppress asking user for permission and instead
         // error in the cases where we would normally need to ask the user.
-        bool onlyIfSilent = false;
+        bool only_if_silent = false;
 
         CborValue params;
         const CborError cberr = cbor_value_map_find_value(&process->ctx.value, CBOR_RPC_TAG_PARAMS, &params);
         if (cberr == CborNoError || cbor_value_is_valid(&params) || cbor_value_is_map(&params)) {
-            rpc_get_boolean("only_if_silent", &params, &onlyIfSilent);
+            // This field is optional and defaults to false if not present (initialized above)
+            only_if_silent = rpc_get_boolean_or("only_if_silent", &params, false);
         }
 
         const char* question[] = { "Export master", "blinding key?" };
-        if (onlyIfSilent || !await_yesno_activity("Blinding Key", question, 2, true, "blkstrm.com/blindingkey")) {
+        if (only_if_silent || !await_yesno_activity("Blinding Key", question, 2, true, "blkstrm.com/blindingkey")) {
             JADE_LOGW("User declined to export master blinding key");
             jade_process_reject_message(
                 process, CBOR_RPC_USER_CANCELLED, "User declined to export master blinding key");
diff --git a/main/process/get_receive_address.c b/main/process/get_receive_address.c
index 9d4c57b..f307293 100644
--- a/main/process/get_receive_address.c
+++ b/main/process/get_receive_address.c
@@ -180,8 +180,7 @@ void get_receive_address_process(void* process_ptr)
             }
         } else if (is_singlesig(script_variant)) {
             // For single-sig the path is explicit in the params
-            rpc_get_bip32_path("path", &params, path, max_path_len, &path_len);
-            if (path_len == 0) {
+            if (!rpc_get_bip32_path("path", &params, path, max_path_len, &path_len) || path_len == 0) {
                 jade_process_reject_message(
                     process, CBOR_RPC_BAD_PARAMETERS, "Failed to extract valid path from parameters");
                 goto cleanup;
diff --git a/main/process/sign_utils.c b/main/process/sign_utils.c
index 25ee20e..22d0084 100644
--- a/main/process/sign_utils.c
+++ b/main/process/sign_utils.c
@@ -222,8 +222,8 @@ bool params_additional_info(jade_process_t* process, CborValue* params, const st
     rpc_get_asset_summary(process, "wallet_input_summary", &additional_info, in_sums, num_in_sums);
     rpc_get_asset_summary(process, "wallet_output_summary", &additional_info, out_sums, num_out_sums);
 
-    // 'partial' flag (defaults to false, set above)
-    rpc_get_boolean("is_partial", &additional_info, is_partial);
+    // 'partial' flag (defaults to false, initially also defaulted above)
+    *is_partial = rpc_get_boolean_or("is_partial", &additional_info, false);
 
     // Tx Type
     if (!rpc_get_txtype(process, &additional_info, txtype)) {
diff --git a/main/usbhmsc/usbmode.c b/main/usbhmsc/usbmode.c
index 6680e83..7a041e5 100644
--- a/main/usbhmsc/usbmode.c
+++ b/main/usbhmsc/usbmode.c
@@ -536,7 +536,8 @@ static bool handle_ota_reply(const uint8_t* msg, const size_t len, void* ctx)
     if (cberr != CborNoError || !rpc_message_valid(&message)) {
         JADE_LOGE("Invalid cbor message");
     } else {
-        rpc_get_boolean("result", &message, ok);
+        // Optional field, but we expect it to be present and true for a positive response
+        *ok = rpc_get_boolean_or("result", &message, false);
     }
 
     // We return true in all cases to indicate that a message was received
diff --git a/main/utils/cbor_rpc.h b/main/utils/cbor_rpc.h
index e546104..05d302f 100644
--- a/main/utils/cbor_rpc.h
+++ b/main/utils/cbor_rpc.h
@@ -29,8 +29,8 @@
 // Plenty for green wallets, bip44 etc. with plenty to spare.
 #define MAX_PATH_LEN 16
 
-bool cbor_print_error_for(const char* id, int code, const char* message, const uint8_t* data, size_t datalen,
-    uint8_t* buffer, size_t buffer_len, size_t* towrite);
+WARN_UNUSED_RESULT bool cbor_print_error_for(const char* id, int code, const char* message, const uint8_t* data,
+    size_t datalen, uint8_t* buffer, size_t buffer_len, size_t* towrite);
 
 // Parse input
 bool rpc_message_valid(const CborValue* message);
@@ -49,20 +49,22 @@ void rpc_get_string(const char* field, size_t max, const CborValue* value, char*
 void rpc_get_raw_bytes_ptr(const CborValue* value, const uint8_t** data, size_t* size);
 void rpc_get_bytes_ptr(const char* field, const CborValue* value, const uint8_t** data, size_t* size);
 void rpc_get_bytes(const char* field, size_t max, const CborValue* value, uint8_t* data, size_t* written);
-bool rpc_get_n_bytes(const char* field, const CborValue* value, size_t expected_size, uint8_t* data);
-bool rpc_get_sizet(const char* field, const CborValue* value, size_t* res);
-size_t rpc_get_sizet_or(const char* field, const CborValue* value, size_t default_value);
-bool rpc_get_uint64_t(const char* field, const CborValue* value, uint64_t* res);
-uint64_t rpc_get_uint64_t_or(const char* field, const CborValue* value, uint64_t default_value);
-bool rpc_get_boolean(const char* field, const CborValue* value, bool* res);
-bool rpc_get_boolean_or(const char* field, const CborValue* value, bool default_value);
 
-bool rpc_get_bip32_path(
+WARN_UNUSED_RESULT bool rpc_get_n_bytes(const char* field, const CborValue* value, size_t expected_size, uint8_t* data);
+WARN_UNUSED_RESULT bool rpc_get_sizet(const char* field, const CborValue* value, size_t* res);
+WARN_UNUSED_RESULT size_t rpc_get_sizet_or(const char* field, const CborValue* value, size_t default_value);
+WARN_UNUSED_RESULT bool rpc_get_uint64_t(const char* field, const CborValue* value, uint64_t* res);
+WARN_UNUSED_RESULT uint64_t rpc_get_uint64_t_or(const char* field, const CborValue* value, uint64_t default_value);
+WARN_UNUSED_RESULT bool rpc_get_boolean(const char* field, const CborValue* value, bool* res);
+WARN_UNUSED_RESULT bool rpc_get_boolean_or(const char* field, const CborValue* value, bool default_value);
+
+WARN_UNUSED_RESULT bool rpc_get_bip32_path(
     const char* field, const CborValue* value, uint32_t* path_ptr, size_t max_path_len, size_t* written);
-bool rpc_get_bip32_path_from_value(CborValue* value, uint32_t* path_ptr, size_t max_path_len, size_t* written);
+WARN_UNUSED_RESULT bool rpc_get_bip32_path_from_value(
+    CborValue* value, uint32_t* path_ptr, size_t max_path_len, size_t* written);
 
-bool rpc_get_array(const char* field, const CborValue* value, CborValue* result);
-bool rpc_get_map(const char* field, const CborValue* value, CborValue* result);
+WARN_UNUSED_RESULT bool rpc_get_array(const char* field, const CborValue* value, CborValue* result);
+WARN_UNUSED_RESULT bool rpc_get_map(const char* field, const CborValue* value, CborValue* result);
 
 // Build response objects
 void rpc_init_cbor(CborEncoder* container, const char* id, size_t id_len);