found another segfault:

this time in batch_set_config

deltachat-jsonrpc/src/lib.rs

@@ -50,4 +50,45 @@ mod tests {
 
         Ok(())
     }
+
+    #[tokio::test(flavor = "multi_thread")]
+    async fn test_batch_set_config() -> anyhow::Result<()> {
+        let tmp_dir = TempDir::new().unwrap().path().into();
+        let accounts = Accounts::new(tmp_dir).await?;
+        let api = CommandApi::new(accounts);
+
+        let (sender, mut receiver) = unbounded::<String>();
+
+        let (client, mut rx) = RpcClient::new();
+        let session = RpcSession::new(client, api);
+        tokio::spawn({
+            async move {
+                while let Some(message) = rx.next().await {
+                    let message = serde_json::to_string(&message)?;
+                    sender.send(message).await?;
+                }
+                let res: Result<(), anyhow::Error> = Ok(());
+                res
+            }
+        });
+
+        {
+            let request = r#"{"jsonrpc":"2.0","method":"add_account","params":[],"id":1}"#;
+            let response = r#"{"jsonrpc":"2.0","id":1,"result":1}"#;
+            session.handle_incoming(request).await;
+            let result = receiver.next().await;
+            println!("{:?}", result);
+            assert_eq!(result, Some(response.to_owned()));
+        }
+        {
+            let request = r#"{"jsonrpc":"2.0","method":"batch_set_config","id":2,"params":[1,{"addr":"","mail_user":"","mail_pw":"","mail_server":"","mail_port":"","mail_security":"","imap_certificate_checks":"","send_user":"","send_pw":"","send_server":"","send_port":"","send_security":"","smtp_certificate_checks":"","socks5_enabled":"0","socks5_host":"","socks5_port":"","socks5_user":"","socks5_password":""}]}"#;
+            let response = r#"{"jsonrpc":"2.0","id":2,"result":null}"#;
+            session.handle_incoming(request).await;
+            let result = receiver.next().await;
+            println!("{:?}", result);
+            assert_eq!(result, Some(response.to_owned()));
+        }
+
+        Ok(())
+    }
 }

node/segfault2.js

@@ -0,0 +1,50 @@
+const { default: dc } = require('./dist')
+
+const ac = new dc('test1233490')
+
+console.log('[1]')
+
+ac.startJsonRpcHandler(console.log)
+
+console.log('[2]')
+console.log(
+  ac.jsonRpcRequest(
+    JSON.stringify({
+      jsonrpc: '2.0',
+      method: 'batch_set_config',
+      id: 3,
+      params: [
+        69,
+        {
+          addr: '',
+          mail_user: '',
+          mail_pw: '',
+          mail_server: '',
+          mail_port: '',
+          mail_security: '',
+          imap_certificate_checks: '',
+          send_user: '',
+          send_pw: '',
+          send_server: '',
+          send_port: '',
+          send_security: '',
+          smtp_certificate_checks: '',
+          socks5_enabled: '0',
+          socks5_host: '',
+          socks5_port: '',
+          socks5_user: '',
+          socks5_password: '',
+        },
+      ],
+    })
+  )
+)
+
+console.log('[3]')
+
+setTimeout(() => {
+  console.log('[4]')
+  ac.close() // This segfaults -> TODO Findout why?
+
+  console.log('still living')
+}, 1000)