It's a good practice to make "-Werror" a default option of your program.

"-Werror" will make all warnings into errors. That means you cannot get you program compiled with even warnings.

Take the following code for example:

/* werror.c
 *
 * complile it with:
 *
 * $ gcc -Werror -o werror werror.c 
 *
 */

/* #include  */

int main(int argc, char *argv[])
{
	printf("Hellow world!\n");

	return 0;
}

Compile it with "-Werror" will result a fail unless you uncomment "#include <stdio.h>":

$ gcc -Werror -o werror werror.c 
cc1: warnings being treated as errors
werror.c: In function ‘main’:
werror.c:13: warning: incompatible implicit declaration of built-in function ‘printf’