String concatenation with sprintf

Projects Programming
1

I always got in troubles when it comes to concatenation on C++, i have a float value im converting to a char array, then im trying to append some text in front of that value, but im getting a "?" as output, here's the code:

int sensorValue = analogRead(A0);
float voltage= sensorValue * (5.0 / 421.0);
char v[6];
dtostrf(voltage, 6, 2, v);
sprintf(_outbuffer,  "VL%s", v);
Serial.println(v);
Serial.println(_outbuffer);

If I print voltage it works and prints the actual float value, but printing v or _outbuffer gave me a "?" as output. What am I doing wrong?

2

6 digits + a terminating NULL won't fit in 6 elements.

sprintf(_outbuffer,  "VL%s", v);

Are we to guess how _outbuffer is defined, and whether it is large enough?

strcat() might be closer to what you are looking for, and certainly lighter-weight.