如何使用匿名结构/联合编译 C 代码?

How to compile C code with anonymous structs / unions?(如何使用匿名结构/联合编译 C 代码?)

问题描述

我可以在 c++/g++ 中做到这一点:

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

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

那么，

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

会起作用.

如何用 gcc 在 c 中做到这一点?我有

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

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

但是我到处都有错误，特别是

But I get errors all around, specifically

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

推荐答案

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

-fms-extensions 将启用您(和我)想要的功能.

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

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