Suppress error in snprintf with a pointer variable (IDFGH-12441)

[gonzalop]

Suppresses the following error:
lib/mqtt5_msg.c:767:17: error: null destination pointer [-Werror=format-truncation=]
767 | snprintf(response_topic, response_topic_size, "%s/%s", property->response_topic, resp_info);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[euripedesrocha]

Hi @gonzalop could you share your configuration? (IDF version, esp_mqtt in use)
Also, your build configuration to trigger this?
I'm trying to reproduce to check if 1edd167 is also a fix for this.

[gonzalop]

I can't reproduce it now :-?. The error is legit when -Werror is on, but I have no idea why it doesn't happen now.. What might have "fixed" it for me is that I switched from Debian trixie to Debian sid a few days ago

That patch you linked would fix the issue too.

Here is the IDF version and my MQTT configuration anyway:

$ idf.py --version
ESP-IDF v5.2.1

And the idf.py menuconfig options for MQTT:

[*] Enable MQTT protocol 3.1.1
[*] Enable MQTT protocol 5.0
[*] Enable MQTT over SSL
[*] Enable MQTT over Websocket
[*]     Enable MQTT over Websocket Secure
[ ] Use Incremental Message Id
[ ] Skip publish if disconnected
[ ] Report deleted messages
[ ] MQTT Using custom configurations
[ ] Enable MQTT task core selection
[ ] Enable custom outbox implementation

[euripedesrocha]

@gonzalop thanks for the info, what about the build configuration? The error/warning is there without the changes I mention, I just wanted to trigger it and confirm that it's fixed, I agree that the changes must fix, but I would like to have it triggered anyway.
I will close this one, since 1edd167 fix the actual bug here.