garbage on mqtt string when setting the buffer

[Rocco83]

Hi,

I have an issue sending out the mqtt message (json). I believe that i'm simply passing the default buffer size (128 byte if i'm not wrong) summing up the topic & message. So, I need to enlarge the buffer on the constructor.

The snippet is the following (full code: https://github.com/Rocco83/caldaia):

  mqttreturn = mqttClient.publish("/caldaia", "debug");
  if ( !mqttreturn ) { Serial.println(F("MQTT short debug send message failed")); } else { Serial.println(F("MQTT short debug easy string OK")); }
  strcpy(json_string, "{\"temperature\":23.63281,\"temperature_unit\":\"°C\",\"pressure\":-0.014143,\"pressure_unit\":\"°C\",\"mqttRawData\":[131");
  mqttreturn = mqttClient.publish("/caldaia", json_string);
  if ( !mqttreturn ) { Serial.println(F("MQTT long debug send message failed")); } else { Serial.println(F("MQTT long debug easy string OK")); }

Without options, this is the footprint on compile:

Sketch uses 30952 bytes (95%) of program storage space. Maximum is 32256 bytes.
Global variables use 1156 bytes (56%) of dynamic memory, leaving 892 bytes for local variables. Maximum is 2048 bytes.

Here comes the problem: 1) setting the constructor to 160 bytes will produce garbage. Output in mosquitto:

debug
{"temperature":23.63281,"temperature_unit":"°C","pressure":-0.014143,"pressure_unit":"°C",*�*�����H

This is the footprint on compile:

Sketch uses 30952 bytes (95%) of program storage space. Maximum is 32256 bytes.
Global variables use 1156 bytes (56%) of dynamic memory, leaving 892 bytes for local variables. Maximum is 2048 bytes.

2) setting the constructor to 256 bytes will not not show anything in mqtt. No output in mosquitto (not even the short one, so "debug"). This is the footprint on compile:

Sketch uses 30952 bytes (95%) of program storage space. Maximum is 32256 bytes.
Global variables use 1156 bytes (56%) of dynamic memory, leaving 892 bytes for local variables. Maximum is 2048 bytes.

As you can see, the footprint is not changing at all, which sounds quite strange to me, as this is a global variable.

I am not sure if this is a bug, but... seems to me so.

[Rocco83]

Brief notice, increasing the buffer (but lowering the footprint of other variables) fixed the issue.

[256dpi]

Closing as solved.