[Mono-list] zero length Marshal.Copy problem

[Aleksey Demakov]

Hi all,

Copying zero-length data to/from unmanaged memory with
Marshal.Copy methods results in the following errors:

** ERROR **: file marshal.c: line 2686 (ves_icall_System_Runtime_InteropServices_Marshal_copy_to_unmanaged): assertion failed: (start_index >= 0 && start_index < mono_array_length (src))
aborting...

or

** ERROR **: file marshal.c: line 2709 (ves_icall_System_Runtime_InteropServices_Marshal_copy_from_unmanaged): assertion failed: (start_index >= 0 && start_index < mono_array_length (dest))
aborting...

The attached files contain a test and a proposed patch for this problem.

Regards,
Aleksey

using System;
using System.Runtime.InteropServices;

public class TestCopy
{
    public static void Main (string[] args)
    {
        IntPtr buffer = Marshal.AllocHGlobal (1024);
        byte[] bytes = UnmarshalBytes (buffer, 0);
        MarshalBytes (buffer, bytes);
    }

    private static void MarshalBytes (IntPtr buffer, byte[] bytes)
    {
        Marshal.Copy (bytes, 0, buffer, bytes.Length);
    }

    private static byte[] UnmarshalBytes (IntPtr buffer, int length)
    {
        byte[] bytes = new byte[length];
        Marshal.Copy (buffer, bytes, 0, length);
        return bytes;
    }
}


Index: marshal.c
===================================================================
RCS file: /mono/mono/mono/metadata/marshal.c,v
retrieving revision 1.67
diff -u -r1.67 marshal.c
--- marshal.c   20 Jan 2003 18:06:01 -0000      1.67
+++ marshal.c   21 Jan 2003 10:08:10 -0000
@@ -2683,7 +2683,8 @@
        MONO_CHECK_ARG_NULL (dest);
 
        g_assert (src->obj.vtable->klass->rank == 1);
-       g_assert (start_index >= 0 && start_index < mono_array_length (src));
+       g_assert (start_index >= 0);
+       g_assert (length >= 0);
        g_assert (start_index + length <= mono_array_length (src));
 
        element_size = mono_array_element_size (src->obj.vtable->klass);
@@ -2706,7 +2707,8 @@
        MONO_CHECK_ARG_NULL (dest);
 
        g_assert (dest->obj.vtable->klass->rank == 1);
-       g_assert (start_index >= 0 && start_index < mono_array_length (dest));
+       g_assert (start_index >= 0);
+       g_assert (length >= 0);
        g_assert (start_index + length <= mono_array_length (dest));
 
        element_size = mono_array_element_size (dest->obj.vtable->klass);