[Mono-list] zero length Marshal.Copy problem

[Aleksey Demakov]

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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

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 name="TestCopy.cs"
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 filename="TestCopy.cs"

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;
    }
}


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 name="marshal.c.patch"
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 filename="marshal.c.patch"

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);

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