This is only seen on Ubuntu. Probably it has something related to how source is compiled, but I can’t get why. Is strcpy() performed multi-threaded/multi-processor way? Anyone can explain?

I have a string, where I search for character and remove it using strcat(). When space char is found at position count, I perform

*(buffer + count) = 0x00;
strcat(buffer, buffer + count + 1);

With ARM this code never has a problem, with x86/Ubuntu I get the following progress

mosquittoQos=1                                  # quality of service
mosquittoQos=1                                 # quality of serviee
mosquittoQos=1                                # quality of servie
mosquittoQos=1                              ## quality of servie

Strings do not overlap at the input, but then overlap as function progresses. This issue does not always happen, and it happens almost always if I run the application as a daemon.