Enhanced switch meta control structure in C

metaswitch.c

#include <stdio.h>
#include <string.h>

#include "metaswitch.h"

int intcmp(const void *x, const void *y)
{
    return *(int *)x - *(int *)y;
}

int main(void)
{
    puts("> switch");

    switch_begin {
    switch_case (1 == 2)
        puts("1 == 2");
        switch_break;
    switch_case (2 == 2)
        puts("2 == 2");
        switch_fallthrough;
    switch_case (3 == 3)
        puts("3 == 3");
        switch_fallthrough;
    switch_default
        puts("default");
        switch_break;
    } switch_end;

    puts("> str switch");

    switch_str_begin ("foo") {
    switch_str_case ("no")
        puts("no");
        switch_str_break;
    switch_str_case ("foo")
        puts("foo");
        switch_str_fallthrough;
    switch_str_case ("bar")
        puts("bar");
        switch_str_break;
    switch_str_default
        puts("default");
        switch_str_break;
    } switch_str_end;

    puts("> eq switch");

    switch_eq_begin (int, 1) {
    switch_eq_case (3)
        puts("3");
        switch_eq_break;
    switch_eq_case (1)
        puts("1");
        switch_eq_fallthrough;
    switch_eq_case (2)
        puts("2");
        switch_eq_break;
    switch_eq_default
        puts("default");
        switch_eq_break;
    } switch_eq_end;

    puts("> cmp switch");

    int x = 1, y = 2, z = 3;

    switch_cmp_begin (intcmp, &x) {
    switch_cmp_case (&y)
        puts("z");
        switch_cmp_break;
    switch_cmp_case (&x)
        puts("x");
        switch_cmp_fallthrough;
    switch_cmp_case (&z)
        puts("z");
        switch_cmp_break;
    switch_cmp_default
        puts("default");
        switch_cmp_break;
    } switch_cmp_end;

    return 0;
}

metaswitch.h

#ifndef METASWITCH_H
#define METASWITCH_H

#define switch_begin           do 
#define switch_case(X)         if (X) {
#define switch_break           break; }
#define switch_fallthrough     }   
#define switch_default         {
#define switch_end             while (0)

#define switch_str_begin(X)    { char __fall = 0; char *__switch_tgt = (char *)(X); switch_begin
#define switch_str_case(X)     switch_case (__fall || !strcmp(X, __switch_tgt))
#define switch_str_break       __fall = 0; break; }
#define switch_str_fallthrough __fall = 1; }
#define switch_str_default     switch_default
#define switch_str_end         switch_end; }

#define switch_eq_begin(T, X) { char __fall = 0; T __switch_tgt = X; switch_begin
#define switch_eq_case(X)     switch_case (__fall || (X) == __switch_tgt)
#define switch_eq_break       __fall = 0; break; }
#define switch_eq_fallthrough __fall = 1; }
#define switch_eq_default     switch_default
#define switch_eq_end         switch_end; }

#define switch_cmp_begin(C, X) { char __fall = 0; void *__switch_tgt = (void *)(X); int (*__cmp)(const void *, const void *) = C; switch_begin
#define switch_cmp_case(X)     switch_case (__fall || !__cmp(X, __switch_tgt))
#define switch_cmp_break       __fall = 0; break; }
#define switch_cmp_fallthrough __fall = 1; }
#define switch_cmp_default     switch_default
#define switch_cmp_end         switch_end; }

#endif