#include <stdio.h>

#include <stdlib.h>

#include <sys/cdefs.h>

// https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/C-Extensions.html

// like templete, generic typed func or macro func

#define max(a,b) \

({ typeof (a) _a = (a); \

typeof (b) _b = (b); \

_a > _b ? _a : _b; }) // can be added generic macro func

#define type_name(type) typeof(type)

int a() {

return 1111111;

}

// there are no references in c. too bad.

int main() {

int result = ({ // this is statement expressions

int x = 5; // can use normal code line

int y = 3;

(void)(x + y);

a(); // return a value of returned a func

// return 1; return ; // cant use return keyword

});

printf("result code block: %d\n", result);

void test1(int a) { printf("result: %d\n", a); } // gnu nested functions!

test1(({

12345; // code block also use when passing to a parameter

}));

printf("999: %p\n", test1);

test1(999);

void test2(void (*a)(int)){

printf("%p\n", a);

(*a)(33333);

}

printf("33333: %p\n", test1);

test2(test1); // nested funcs can pass to another. + error

void (*fp)() = ({ void f(){printf("im func as a compount literal\n");};&f; });

fp();

({ void f(){printf("im func as a compount literal\n");} f; })();

int (*foo(void))[2] { // vla return

return &(int[2]){1,2};

}

int arr = (*foo())[0];

struct {

int type;

int size;

char content[0];

} *st1 = malloc(sizeof(st1) + 100); // 100 is content size

free(st1);

struct yy {

char a1: 1;

char a2: 1;

char a3: 1;

char a4: 1;

char a5: 1;

char a6: 1;

char a7: 2; // 2 !

char b1: 1; // add new char 1 byte padding

char b2: 1;

}; // total 2 byte, different types increase padding

    (int[33]){

[2] = ({

int x = 5, y = 10;

x * y;

}),

['A' != 'A' ? : 23] = 3 // gnu Omitted Operands (5.7)

} [0] = 1;

int a[6] = {[0 ... 5] = 666}; // syntactic sugar fill array

// https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html

for (size_t i = 0; i < 6; i++) printf("%d\n", a[i]);

char c = 66;

switch(c) {

case '0' ... '9': // multiple int match, gnu extension

printf("[%c] is a number.\n", c);

break;

case 'a' ... 'z':

printf("[%c] is a lowercase letter.\n", c);

break;

case 'A' ... 'Z':

printf("[%c] is an uppercase letter.\n", c);

break;

default:

printf("[%c] is not a valid character!\n", c);

break;

}

return 0;

}

// cleanup (cleanup_function)