Why can't you declare a variable inside a case?

Question:

Why doesn't this compile?

#include <stdio.h>

int main(void) {
    int valor = 0;
    scanf("%d", &valor);
    switch (valor) {
    case 0:
        int variavel = 1;
        printf("%d", variavel);
        break;
    default:
        int variavel = 2;
        printf("%d", variavel);
    }
}

Answer:

A very common mistake is for people to think that the case is a command block and generates a new scope. Actually the case is just a label . So it's just a name for an address of the code used to trigger a diversion. In fact a switch is just a goto based on a value.

This already works:

#include <stdio.h>

int main(void) {
    int valor = 0;
    scanf("%d", &valor);
    switch (valor) {
    case 0: {
        int variavel = 1;
        printf("%d", variavel);
        break;
    } default: {
        int variavel = 2;
        printf("%d", variavel);
    }
    }
}

See working on ideone . And on repl.it. Also posted on GitHub for future reference .

The braces create a block and a scope, then you can create variables.