[G4:~/testgpcadriaan] adriaan% cat NoUnderscore.p program NoUnderscore; procedure _Run; begin writeln('_Run') end; begin _Run end. [G4:~/testgpcadriaan] adriaan% gpc NoUnderscore.p NoUnderscore.p:4: warning: identifiers should not start with an underscore [G4:~/testgpcadriaan] adriaan% gpc NoUnderscore.p -Wno-underscore [G4:~/testgpcadriaan] adriaan% gpc NoUnderscore.p --gnu-pascal -Wno-underscore NoUnderscore.p:4: warning: identifiers should not start with an underscore So, it seems that -Wno-underscore is broken when used with --gnu-pascal. Regards, Adriaan van Os