initialize a union array at declaration

Question

I'm trying to initialize the following union array at declaration: ``` 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}}}; ``` But I'getting the following error: ``` 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:…

Accepted Answer

Quoting 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.

So, either put the `float` array first, or if possible use C99 and write:

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

The important thing being the `.f`.

initialize a union array at declaration

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