Exploring (void)variable for supressing warnings

martian.honey

lappy:~ aaron$ cat a.C
int main(void) {
    int a = 1 + 1;
}
lappy:~ aaron$ clang a.C -Wall
a.C:2:9: warning: unused variable 'a' [-Wunused-variable]
    int a = 1 + 1;
        ^
1 warning generated.
lappy:~ aaron$ vim a.C
lappy:~ aaron$ cat aclang a.C -Wall
lappy:~ aaron$ cat a.C
int main(void) {
    int a = 1 + 1;
    a;
}
lappy:~ aaron$ clang a.C -Wall
a.C:3:5: warning: expression result unused [-Wunused-value]
    a;
    ^
1 warning generated.
lappy:~ aaron$ vim a.C 
lappy:~ aaron$ cat a.C        
int main(void) {
    int a = 1 + 1;
    (void) a;
}
lappy:~ aaron$ clang a.C -Wall
lappy:~ aaron$