test.c:31:2: error: expected declaration or statement at end of input return 0;

This error message is indicating that there is a problem with the syntax of your code in test.c. The compiler is expecting another statement or declaration to follow the line that contains "return 0;", but it has reached the end of the file without finding anything.

To fix this error, you should check your code to make sure that all of your statements and declarations are properly closed and that there are no missing or extra brackets, parentheses, or semicolons. Also, make sure that you have included any necessary header files and that all functions are properly defined and declared.