How to write commands in a GDB script that get executed every time a particular brkpt is hit ?

Answer 1

You are probably not placing the commands on the breakpoint you think you are.

If I were you, I'd modify the script to the following:

define setup
   handle SIGTRAP noprint nostop
   br 'Class1::Fun1(void)'
   run
   br 'Class2::Run(void)'
   c
   br Function2
   commands
     return 0 
     c
   end
end

If no breakpoint target is given, commands associates with the most recent breakpoint. This way, no matter what other breakpoints you have in your gdb session, your commands will be associated with the breakpoint at Function2.