Fix crash when converting 0-length Go []byte to Python bytes

_examples/gobytes/test.py

@@ -15,4 +15,11 @@
 print("Python bytes to Go: ", go.Slice_byte.from_bytes(a))
 print("Go bytes to Python: ", bytes(go.Slice_byte([3, 4, 5])))
 
+# Regression test for issue #359: 0-length slice must not crash
+empty = gobytes.CreateBytes(0)
+print("Go empty slice: ", empty)
+empty_bytes = bytes(empty)
+assert empty_bytes == b"", f"expected b'', got {empty_bytes!r}"
+print("Go empty bytes to Python: ", empty_bytes)
+
 print("OK")

bind/gen_slice.go

@@ -411,6 +411,11 @@ otherwise parameter is a python list that we copy from
 			g.gofile.Printf("func Slice_byte_to_bytes(handle CGoHandle) *C.PyObject {\n")
 			g.gofile.Indent()
 			g.gofile.Printf("s := deptrFromHandle_Slice_byte(handle)\n")
+			g.gofile.Printf("if len(s) == 0 {\n")
+			g.gofile.Indent()
+			g.gofile.Printf("return C.PyBytes_FromStringAndSize(nil, 0)\n")
+			g.gofile.Outdent()
+			g.gofile.Printf("}\n")
 			g.gofile.Printf("ptr := unsafe.Pointer(&s[0])\n")
 			g.gofile.Printf("size := len(s)\n")
 			if WindowsOS {

main_test.go

@@ -282,6 +282,8 @@ Go slice:  go.Slice_byte len: 10 handle: 1 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 gobytes.HashBytes from Go bytes: gobytes.Array_4_byte len: 4 handle: 2 [12, 13, 81, 81]
 Python bytes to Go:  go.Slice_byte len: 4 handle: 3 [0, 1, 2, 3]
 Go bytes to Python:  b'\x03\x04\x05'
+Go empty slice:  go.Slice_byte len: 0 handle: 5 []
+Go empty bytes to Python:  b''
 OK
 `),
 	})