Go into project properties. Search for C/C++Build -> Settings. In the Tool Settings tab search for GCC C compiler and then Miscellaneous. In other flags text box add the -std=c99. It should work fine.
Go into project properties. Search for C/C++Build -> Settings. In the Tool Settings tab search for GCC C compiler and then Miscellaneous. In other flags text box add the -std=c99. It should work fine.