gcc -Wall enables all compiler's warning messages. This option should always be used, in order to generate better code.
Syntax
$ gcc -Wall [options] [source files] [object
files] [-o output file]
Example
Write source file myfile.c:
// myfile.c #include int main() {
printf("Program run!\n"); int i=10; }
Regular build of myfile.c gives no messages:
$ gcc myfile.c -o myfile $
Build of myfile.c with -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 $