replace direct use of reflect.SliceHeader with cast; avoid zero-byte …

…allocation (#117)

tmpl/conversions.tmpl

@@ -98,14 +98,13 @@ func Strs(strs ...string) (cstrs **uint8, free func()) {
 	for i := range strs {
 		n += len(strs[i])
 	}
+	if n == 0 {
+		n = 1 // avoid allocating zero bytes in case all strings are empty.
+	}
 	data := C.malloc(C.size_t(n))
 
 	// Copy all the strings into data.
-	dataSlice := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-		Data: uintptr(data),
-		Len:  n,
-		Cap:  n,
-	}))
+	dataSlice := (*[1 << 30]byte)(data)[:n]
 	css := make([]*uint8, len(strs)) // Populated with pointers to each string.
 	offset := 0
 	for i := range strs {