Составные литералы (начиная с C99)

(const char []){"abc"} == "abc" // might be 1 or 0, unspecified

#include <assert.h>

int main(void)
{
    struct S
    {
        int i;
    }
    *p = 0, *q;
    int j = 0;
again:
    q = p,
    p = &((struct S){ j++ }); // creates an unnamed object of type S,
                              // initializes it to the value formerly
                              // held in j, then assigns the address
                              // of this unnamed object to the pointer p
    if (j < 2)
        goto again; // note: if a loop were used, it would end scope here,
                    // which would terminate the lifetime of the compound
                    // literal leaving p as a dangling pointer
    assert(p == q && q->i == 1);
}

#include <stdio.h>

int *p = (int[]){2, 4}; // creates an unnamed static array of type int[2]
                        // initializes the array to the values {2, 4}
                        // creates pointer p to point at the first element of
                        // the array
const float *pc = (const float []){1e0, 1e1, 1e2}; // read-only compound literal

struct point {double x,y;};

int main(void)
{
    int n = 2, *p = &n;
    p = (int [2]){*p}; // creates an unnamed automatic array of type int[2]
                       // initializes the first element to the value formerly
                       // held in *p
                       // initializes the second element to zero
                       // stores the address of the first element in p

    void drawline1(struct point from, struct point to);
    void drawline2(struct point *from, struct point *to);
    drawline1(
        (struct point){.x=1, .y=1},  // creates two structs with block scope and
        (struct point){.x=3, .y=4}); // calls drawline1, passing them by value
    drawline2(
        &(struct point){.x=1, .y=1},  // creates two structs with block scope and
        &(struct point){.x=3, .y=4}); // calls drawline2, passing their addresses
}

void drawline1(struct point from, struct point to)
{
    printf("drawline1: `from` @ %p {%.2f, %.2f}, `to` @ %p {%.2f, %.2f}\n",
        (void*)&from, from.x, from.y, (void*)&to, to.x, to.y);
}

void drawline2(struct point *from, struct point *to)
{
    printf("drawline2: `from` @ %p {%.2f, %.2f}, `to` @ %p {%.2f, %.2f}\n",
        (void*)from, from->x, from->y, (void*)to, to->x, to->y);
}

Возможный вывод:

drawline1: `from` @ 0x7ffd24facea0 {1.00, 1.00}, `to` @ 0x7ffd24face90 {3.00, 4.00}
drawline2: `from` @ 0x7ffd24facec0 {1.00, 1.00}, `to` @ 0x7ffd24faced0 {3.00, 4.00}