gcc -Wall aktiverer alle kompilators advarsler. Denne mulighed skal altid bruges for at generere bedre kode.
$ gcc -Wall [options] [source files] [object files] [-o output file]
Skriv kildefil myfile.c :
// myfile.c
#include <stdio.h/
int main()
{
printf("Program run!\n");
int i=10;
}
Regelmæssig build af myfile.c giver ingen beskeder:
$ gcc myfile.c -o myfile
$
Byg af myfile.c med -Wall :
$ gcc -Wall myfile.c -o myfile
myfile.c In function 'main':
myfile.c:6:6: warning: unused variable 'i'
myfile.c:7:1: warning: control reaches end of non-void function
$