If you enable the Extra Commas setting, the compiler generates a warning when it encounters an extra comma. For example, this statement is legal in C but generates a warning when you enable this setting:
int a[] = { 1, 2, 3, 4, }; // ^ WARNING: Extra comma after 4
The Extra Commas setting corresponds to the pragma warn_extracomma. To check this setting, use __option (warn_extracomma).
See Checking Option Settings for information on how to use this directive.