send: assert that Curl_write_plain() has a ->conn when called

To help catch bad invokes.

Closes #6476

diff --git a/lib/sendf.c b/lib/sendf.c
index e756f1ca1f236a2a1669af8644193afc39a8eea3..5075c54394aac54b18f01048b461b51a26a39081 100644 (file)
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -406,7 +406,9 @@ CURLcode Curl_write_plain(struct Curl_easy *data,
 {
   CURLcode result;
   struct connectdata *conn = data->conn;
-  int num = (sockfd == conn->sock[SECONDARYSOCKET]);
+  int num;
+  DEBUGASSERT(conn);
+  num = (sockfd == conn->sock[SECONDARYSOCKET]);
 
   *written = Curl_send_plain(data, num, mem, len, &result);