7.6.1.7 Warnings
-Wall
Show all warnings.
-Werror
Show warnings as errors.
-fsyntax-only
Check the code for syntax errors but don't do anything beyond that.
-pedantic
Issue all the warnings demanded by strict ISO C. Reject all programs that use forbidden extensions and some other programs that do not follow ISO C. Valid ISO C programs should compile properly with or without this option (though a rare few will require -ansi or a -std option specifying the required version of ISO C). However, without this option, some GNU extensions and standard C features are supported as well. With this option, they are rejected.
-pedantic-errors
Pedantic warnings are produced as errors.
-w
Inhibit all warning messages.