如何初始化联盟？

*p = {var1,var2..};

union Ptrlist
{
        Ptrlist *next;
            State *s;
};

Ptrlist *l;
l = allocate_space();
*l = {NULL};

expected expression before ‘{’ token

在C99中,您可以使用d esignated union initializer：

union {
      char birthday[9];
      int age;
      float weight;
      } people = { .age = 14 };

在C,unions can have constructors.

在C89中,你必须明确地做.

typedef union {
  int x;
  float y;
  void *z;
} thing_t;

thing_t foo;
foo.x = 2;

顺便说一句,你是否知道在C联合会,all the members share the same memory space？

int main () 
{
   thing_t foo;
   printf("x: %p  y: %p  z: %p\n",&foo.x,&foo.y,&foo.z );
   return 0;
}

输出：