Prepare your program for Memcheck

• Compile your program with -g to include debugging information so that Memcheck's error messages include exact line numbers. 
• Using -O0 is also a good idea, if you can tolerate the slowdown. 
• With -O1 line numbers in error messages can be inaccurate, although generally speaking running Memcheck on code compiled at -O1 works fairly well, and the speed improvement compared to running -O0 is quite significant. 
• Use of -O2 and above is not recommended as Memcheck occasionally reports uninitialised-value errors which don't really exist.