c - 在自身内部定义结构对象的问题

Question

这个有效:

struct LD__32
{
   struct LD__32 *ld;
};

但这不是:

struct LD_32
{
   struct LD_32 ld;
};

这是为什么？正如 pmg 猜测的那样，我正在将它编译为 C++ 代码。已编辑

Answer 1

C 中的结构不能包含类型不完整的成员。

在后一种情况下，您不能在 LD_32 定义中定义 LD_32 ld;，因为结构 LD_32 尚未定义那个点。

检查 C 中关于结构的containts

第 6.7.2.1/2 节

A structure or union shall not contain a member with incomplete or function type (hence, a structure shall not contain an instance of itself, but may contain a pointer to an instance of itself), except that the last member of a structure with more than one named member may have incomplete array type; such a structure (and any union containing, possibly recursively, a member that is such a structure) shall not be a member of a structure or an element of an array.