How to Safely Access a C Char Array in Go using cgo?

Accessing C Char Array in Go with cgo

In C, we often encounter arrays of constant character pointers (e.g., const char *myStringArray[]). Accessing such arrays from Go using cgo can prove challenging.

Incorrect Approach:

Initially, you may attempt to index the array directly using unsafe pointer arithmetic:

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

However, this approach will navigate through characters within a string, not the array itself.

Correct Solution:

A more reliable solution involves converting the C array into a Go slice.

// Define array size
arraySize := 3

// Create Go slice
cStrings := (*[1 << 30]*C.char)(unsafe.Pointer(&C.myStringArray))[:arraySize:arraySize]

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

This approach ensures proper indexing of the array, providing access to each string element in its entirety.

By understanding the intricacies of pointer manipulation and the utility of Go slices, you can effectively bridge the gap between C and Go memory structures.

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