Garbled log

[Junsoo0607]

Hello，
My project uses libcoap version 4.3.4. When calling the coap_send interface, it returns COAP_INVALID_MID. I noticed that there is a native print statement before printing the return value, but it displays as garbled text. Even though the log encoding is set to UTF-8, the log cannot be viewed. The code also calls the following two interfaces:

coap_set_log_level(LOG_ERR);
coap_set_log_handler(CoapResourceSaveLog);

[mrdeep1]

You do not specify what platform / OS you are running your code on. It would appear that the strerror() function is returning the garbage that you are seeing. libcoap would be expecting the returned data from strerror() to be a null terminated ascii string as it is printing it with '%s'.

[Junsoo0607]

You do not specify what platform / OS you are running your code on. It would appear that the strerror() function is returning the garbage that you are seeing. libcoap would be expecting the returned data from strerror() to be a null terminated ascii string as it is printing it with '%s'.

My code will run on Windows 11. Do you mean that I need to manually concatenate an empty string to the message parameter?

[mrdeep1]

It looks like this code is causing your issues in src/coap_io.c

#ifdef _WIN32
const char *
coap_socket_format_errno(int error) {
  static char szError[256];
  if (FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                    NULL, (DWORD)error, MAKELANGID(LANG_NEUTRAL,
                                                   SUBLANG_DEFAULT), (LPSTR)szError, (DWORD)sizeof(szError),
                    NULL) == 0)
    strcpy(szError, "Unknown error");
  return szError;
}

where I suspect for your locale it is returning WCHAR characters. Not immediately sure how to fix this.

[mrdeep1]

Can you please try #1559 to see if this cures what you are seeing.

[mrdeep1]

Can this be closed now?

[Junsoo0607]

Can this be closed now?

I tried to add maintenance logs in the send_coap(), but I am currently unable to print any logs.

[mrdeep1]

As you have set coap_set_log_level(LOG_ERR);, only log levels higher than COAP_LOG_ERR will get logged.

If you change coap_log_info("Junsoo test coap_send\n"); to coap_log_err("Junsoo test coap_send\n"); then you should get some log output.