如何编译C code。与匿名结构/联合？ [英] How to compile C code with anonymous structs / unions?

问题描述

我可以在C做++ / g ++的：

 结构VEC3 {
    工会{
        结构{
            浮动的x，y和z;
        };
        浮动的xyz [3];
    };
};
 

然后，

  VEC3伏;
断言（安培; v.xyz [0] ==＆安培; V.X）;
断言（安培; v.xyz [1] ==＆安培; V.Y）;
断言（安培; v.xyz [2] ==＆放大器;的v.z）;
 

将工作。

如何用gcc做这在C？我有

  typedef结构{
    工会{
        结构{
            浮动的x，y和z;
        };
        浮动的xyz [3];
    };
}的Vector3;
 

但我得到的错误周围的一切，特别是

  5号线：警告：申报不申报任何东西
7号线：警告：申报不申报任何东西
 

解决方案

根据<一个href=\"http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed-Fields\">http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed-Fields

-fms的扩展将使你（我）希望该功能。

I can do this in c++/g++:

struct vec3 { 
    union {
        struct {
            float x, y, z;
        }; 
        float xyz[3];
    }; 
};

Then,

vec3 v;
assert(&v.xyz[0] == &v.x);
assert(&v.xyz[1] == &v.y);
assert(&v.xyz[2] == &v.z);

will work.

How does one do this in c with gcc? I have

typedef struct {
    union {
        struct {
            float x, y, z;
        };
        float xyz[3];
    };
} Vector3;

But I get errors all around, specifically

line 5: warning: declaration does not declare anything
line 7: warning: declaration does not declare anything

解决方案

according to http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed-Fields

-fms-extensions will enable the feature you (and I) want.

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