是否可以编写C函数来修改Go代码中定义的类型的结构？

Question

This is a follow-up to this question. I made an assumption there that might not be true, which is why I am explicitly asking about it. Because I forgot to ask if this is actually possible, I have already filed issue #8114 about this.

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With cgo, it is possible to have Go code operate on C types, like this:

package foo

//#include <sys/stat.h>
import "C"

func fileSizeFromStat(stat *C.struct_stat) int64 {
    return int64(stat.st_size)
}

Is the reverse possible? I.e. writing C functions that operate on go types? The concrete point of this is outlined in the question linked above; I want to marshall C structures that cannot be accessed from Go code, either because they use unions or bitfields or because their alignment makes them incompatible with Go code.

Answer 1

As far as I know, no, you can't.

But you could use something ugly like https://github.com/OneOfOne/go-nfqueue/blob/master/nfqueue.go#L130 where you export a Go function that takes a lot of pointers and construct your Go struct in go.