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      1 // struct definition and declaration
      2 struct a {
      3     int a;
      4     int b;
      5 } c;
      6 
      7 // Useless, but legal struct declaration
      8 struct {
      9     int x;
     10 };
     11 
     12 // Useful anonymous struct declaration
     13 struct {
     14     int y;
     15 } anon1, anon2;
     16 
     17 // forward declarations
     18 struct a;
     19 struct b;
     20 struct c;
     21 
     22 struct b {int a; int b; };
     23 
     24 // struct c {b g; }; // syntax error.
     25 
     26 // struct s {float c,a,b,c;} s; // duplicate struct member
     27 
     28 struct c {struct b g; };
     29 
     30 // struct a { int w; }; // error
     31 
     32 void testCopying() {
     33     struct a {int a[10]; char c;} a, b;
     34     a.c = 37;
     35     b.c = 38;
     36     b = a;
     37     printf("testCopying: %d == %d\n", a.c, b.c);
     38 }
     39 
     40 void testUnion() {
     41     union u;
     42     union u {float f;int i;} u;
     43     u.f = 1.0f;
     44     printf("testUnion: %g == 0x%08x\n", u.f, u.i);
     45 }
     46 
     47 struct v {float x, y, z, w; };
     48 
     49 void add(struct v* result, struct v* a, struct v* b) {
     50     result->x = a->x + b->x;
     51     result->y = a->y + b->y;
     52     result->z = a->z + b->z;
     53     result->w = a->w + b->w;
     54 }
     55 
     56 void set(struct v* v, float x, float y, float z, float w) {
     57     v->x = x;
     58     v->y = y;
     59     v->z = z;
     60     v->w = w;
     61 }
     62 
     63 void print(struct v* v) {
     64     printf("(%g, %g, %g, %g)\n", v->x, v->y, v->z, v->w);
     65 }
     66 
     67 void testArgs() {
     68     struct v a, b, c;
     69     set(&a, 1.0f, 2.0f, 3.0f, 4.0f);
     70     set(&b, 5.0f, 6.0f, 7.0f, 8.0f);
     71     add(&c, &a, &b);
     72     printf("testArgs: ");
     73     print(&c);
     74 }
     75 
     76 int main() {
     77     anon1.y = 3;
     78     anon2.y = anon1.y;
     79 
     80     testCopying();
     81     testUnion();
     82     testArgs();
     83 
     84     struct c cc;
     85     cc.g.a = 3;
     86     c.a = 1;
     87     c.b = 3;
     88     struct a {int x, y; } z;
     89     // struct a {int x, y; } z2;
     90     z.x = c.a;
     91     struct a *pA;
     92     pA = &z;
     93     pA->x += 5;
     94     return pA->x;
     95 }
     96