From fee6de6a7f010e8653656b01635ddf48c513198e Mon Sep 17 00:00:00 2001
From: cpq <valenok@gmail.com>
Date: Fri, 19 Aug 2022 15:07:50 +0100
Subject: [PATCH] Allow NULL head in struct mg_rpc

---
 mongoose.c       |  2 +-
 src/rpc.c        |  2 +-
 test/unit_test.c | 13 +++++++++++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/mongoose.c b/mongoose.c
index 480bb312..7186494e 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3580,7 +3580,7 @@ void mg_rpc_process(struct mg_rpc_req *r) {
   int len, off = mg_json_get(r->frame, "$.method", &len);
   if (off > 0 && r->frame.ptr[off] == '"') {
     struct mg_str m = mg_str_n(&r->frame.ptr[off + 1], (size_t) len - 2);
-    struct mg_rpc *h = *(struct mg_rpc **) r->head;
+    struct mg_rpc *h = r->head == NULL ? NULL : *r->head;
     while (h != NULL && !mg_match(m, h->method, NULL)) h = h->next;
     if (h != NULL) {
       r->rpc = h;
diff --git a/src/rpc.c b/src/rpc.c
index c513a555..c35e9c5e 100644
--- a/src/rpc.c
+++ b/src/rpc.c
@@ -24,7 +24,7 @@ void mg_rpc_process(struct mg_rpc_req *r) {
   int len, off = mg_json_get(r->frame, "$.method", &len);
   if (off > 0 && r->frame.ptr[off] == '"') {
     struct mg_str m = mg_str_n(&r->frame.ptr[off + 1], (size_t) len - 2);
-    struct mg_rpc *h = *(struct mg_rpc **) r->head;
+    struct mg_rpc *h = r->head == NULL ? NULL : *r->head;
     while (h != NULL && !mg_match(m, h->method, NULL)) h = h->next;
     if (h != NULL) {
       r->rpc = h;
diff --git a/test/unit_test.c b/test/unit_test.c
index 124aa659..dda44f1a 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -2524,6 +2524,19 @@ static void test_rpc(void) {
     mg_iobuf_free(&io);
   }
 
+  {
+    const char *resp =
+        "{\"id\":true,\"error\":{\"code\":-32601,\"message\":\"foo not "
+        "found\"}}";
+    req.frame = mg_str("{\"id\": true,\"method\":\"foo\"}");
+    req.head = NULL;
+    mg_rpc_process(&req);
+    // MG_INFO(("-> %s", io.buf));
+    ASSERT(strcmp((char *) io.buf, resp) == 0);
+    mg_iobuf_free(&io);
+    req.head = &head;
+  }
+
   {
     const char *resp = "{\"error\":{\"code\":-32700,\"message\":\"haha\"}}";
     req.frame = mg_str("haha");