Access C array of type const char * from Go

I have a C file with an array of type const char *, lets call it myStringArray[], something like:

const char *myStringArray[] = {
  "NAME_OF_FIRST_THING",
  "NAME_OF_SECOND_THING",
  "NAME_OF_THIRD_THING"}

I need Go to index into that C array, using cgo, and convert an array entry into a Go string. The following code compiles but does not work correctly; you can see from the output that follows, it is indexing along the strings rather than up the array:

myGoString := C.GoString((*C.char) (unsafe.Pointer(uintptr(unsafe.Pointer(C.myStringArray)) + uintptr(index) * unsafe.Sizeof(C.myStringArray))))

...result being this:

NAME_OF_FIRST_THING

FIRST_THING

ING

FYI, the purpose of this is to decode on a server a log file that was created on an embedded platform running C, hence the need to re-use the same logging index files.

I've been stabbing at this randomly for a few hours now without success. Can anyone correct my construction, or provide an alternative?

Solution

While you could do the pointer arithmetic yourself, it's safer and more convenient to convert the C array into a Go slice first.

arraySize := 3
cStrings := (*[1 << 30]*C.char)(unsafe.Pointer(&C.myStringArray))[:arraySize:arraySize]

for _, cString := range cStrings {
    fmt.Println(C.GoString(cString))
}

// prints:
// NAME_OF_FIRST_THING
// NAME_OF_SECOND_THING
// NAME_OF_THIRD_THING

Relevant cgo wiki entry: https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices