I was wondering if anyone knew what the flags for gcc would be to replicate or be as closely to the warnings for the compiler that is used by Pelles?
I don't know exactly how to mimic PellesC behavior on warnings with GCC, but you can proceed by tentative switches which control the warnings production:
http://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Warning-Options.html#Warning-Options
Maybe -Wall can be near enough.
As far as I know GCC doesn't have the same "recommending" warnings which tell you about code style issues and the like if you mean that. Of course, there are many useful options available. Say PellesC has some unique 'comfort' functions.