c - 在声明时初始化 union 数组

Question

我正在尝试在声明时初始化以下 union 数组:

typedef union { __m128d m;  float f[4]; } mat;
mat m[2] = { {{30467.14153,5910.1427,15846.23837,7271.22705},
{30467.14153,5910.1427,15846.23837,7271.22705}}};

但我收到以下错误:

matrix.c: In function ‘main’:
matrix.c:21: error: incompatible types in initialization
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[0]’)
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[0]’)
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[0]’)
matrix.c:21: error: incompatible types in initialization
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[1]’)
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[1]’)
matrix.c:21: warning: excess elements in union initializer
matrix.c:21: warning: (near initialization for ‘m[1]’)

Answer 1

引用 this page :

With C89-style initializers, structure members must be initialized in the order declared, and only the first member of a union can be initialized.

因此，要么将 float 数组放在第一位，要么尽可能使用 C99 并编写:

mat m[2] = { { .f = { /* and so on */ } }, /* ... */ };

重要的是 .f。