Valid, but worthless syntax in switch-case?

Question

Through a little typo, I accidentally found this construct:

int main(void) {
    char foo = \'c\';

    switch(foo)
    {
        printf(\"Cant Touch This\\n\");         


        

Answer 1

You got your answer related to the required gcc option -Wswitch-unreachable to generate the warning, this answer is to elaborate on the usability / worthyness part.

Quoting straight out of C11, chapter §6.8.4.2, (emphasis mine)

switch (expr)
{
int i = 4;
f(i);
case 0:
i = 17;
/* falls through into default code */
default:
printf("%d\n", i);
}

the object whose identifier is i exists with automatic storage duration (within the block) but is never initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will access an indeterminate value. Similarly, the call to the function f cannot be reached.

Which is very self-explanatory. You can use this to define a locally scoped variable which is available only within the switch statement scope.