New repl command: send-garbage

This new command attempts to send malformed utf8 string to current chat with
dc_send_text_msg() function. Currently, instead of error code it causes
application crash with following backtrace:

thread 'main' panicked at 'Non utf8 string: '[255]' (Utf8Error { valid_up_to: 0, error_len: Some(1) })', src/dc_t
ools.rs:1571:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   8: std::panicking::begin_panic_fmt
             at src/libstd/panicking.rs:339
   9: deltachat::dc_tools::as_str::{{closure}}
             at src/dc_tools.rs:1571
  10: core::result::Result<T,E>::unwrap_or_else
             at /rustc/0b680cfce544ff9a59d720020e397c4bf3346650/src/libcore/result.rs:818
  11: deltachat::dc_tools::as_str
             at src/dc_tools.rs:1570
  12: deltachat::dc_chat::prepare_msg_raw
             at src/dc_chat.rs:726
  13: deltachat::dc_chat::prepare_msg_common
             at src/dc_chat.rs:461
  14: deltachat::dc_chat::dc_send_msg
             at src/dc_chat.rs:905
  15: deltachat::dc_chat::dc_send_text_msg
             at src/dc_chat.rs:981
  16: repl::cmdline::dc_cmdline
             at examples/repl/cmdline.rs:955
  17: repl::handle_cmd
             at examples/repl/main.rs:566
  18: repl::main_0
             at examples/repl/main.rs:445
  19: repl::main
             at examples/repl/main.rs:578
  20: std::rt::lang_start::{{closure}}
             at /rustc/0b680cfce544ff9a59d720020e397c4bf3346650/src/libstd/rt.rs:64
  21: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  22: std::panicking::try::do_call
             at src/libstd/panicking.rs:296
  23: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:82
  24: std::panicking::try
             at src/libstd/panicking.rs:275
  25: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  26: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  27: std::rt::lang_start
             at /rustc/0b680cfce544ff9a59d720020e397c4bf3346650/src/libstd/rt.rs:64
  28: main
  29: __libc_start_main
  30: _start

examples/repl/cmdline.rs

@@ -450,6 +450,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                  dellocations\n\
                  getlocations [<contact-id>]\n\
                  send <text>\n\
+                 send-garbage\n\
                  sendimage <file> [<text>]\n\
                  sendfile <file>\n\
                  draft [<text>]\n\
@@ -948,6 +949,16 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                 bail!("Sending failed.");
             }
         }
+        "send-garbage" => {
+            ensure!(!sel_chat.is_null(), "No chat selected.");
+            let msg = b"\xff\x00"; // NUL-terminated C-string, that is malformed utf-8
+            if 0 != dc_send_text_msg(context, dc_chat_get_id(sel_chat), msg.as_ptr().cast()) {
+                println!("Malformed utf-8 succesfully send. Not nice.");
+            } else {
+                bail!("Garbage sending failed, as expected.");
+            }
+
+        }
         "sendempty" => {
             ensure!(!sel_chat.is_null(), "No chat selected.");
             if 0 != dc_send_text_msg(

examples/repl/main.rs

@@ -3,6 +3,7 @@
 //!
 //! Usage:  cargo run --example repl --release -- <databasefile>
 //! All further options can be set using the set-command (type ? for help).
+#![feature(ptr_cast)]
 
 #[macro_use]
 extern crate deltachat;
@@ -290,7 +291,7 @@ const DB_COMMANDS: [&'static str; 11] = [
     "housekeeping",
 ];
 
-const CHAT_COMMANDS: [&'static str; 24] = [
+const CHAT_COMMANDS: [&'static str; 25] = [
     "listchats",
     "listarchived",
     "chat",
@@ -308,6 +309,7 @@ const CHAT_COMMANDS: [&'static str; 24] = [
     "dellocations",
     "getlocations",
     "send",
+    "send-garbage",
     "sendimage",
     "sendfile",
     "draft",