Replying to myself here Using the output from this small program
using System; namespace ConsoleApplication4 { enum Ptr : long { } class Program { static unsafe void Main(string[] args) { IntPtr test = new IntPtr(0xffffffff); Ptr testLong = (Ptr)test.ToInt64(); Console.WriteLine("test = {0}, testLong={1}", test, testLong); IntPtr testAnother = (IntPtr)testLong; Console.WriteLine("testAnother = {0}", testAnother); void* p = test.ToPointer(); Console.WriteLine("p = {0}", (long)p); } } } You will see that under MS.NET the output is test = 4294967295, testLong=4294967295 testAnother = 4294967295 p = 4294967295 note the complete absence of sign extended values. The output from Mono on OpenSuse 11.0 Linux test = -1, testLong=-1 testAnother = -1 p = 4294967295 So the pointer conversion from void* to long is not sign extending under Mono, and it is different output to MS.NET. Russell -----Original Message----- From: mono-devel-list-boun...@lists.ximian.com [mailto:mono-devel-list-boun...@lists.ximian.com] On Behalf Of russell....@realtimeworlds.com Sent: 11 February 2009 15:45 To: robe...@gmx.net; mono-devel-list@lists.ximian.com Subject: Re: [Mono-dev] Patch for IntPtr bug We get addresses on Linux that are >2Gb from malloc in the native code, if we go through the conversion from int (i.e.)IntPtr.ToInt64() is not giving a sign extended value back when this happens and then a cast to IntPtr will fail. The cast from a pointer i.e. void* or byte* will also not sign extend the long. The conversion is not sign extending the long (perhaps because it does actually fit)... My patch is correct. Russell -----Original Message----- From: mono-devel-list-boun...@lists.ximian.com [mailto:mono-devel-list-boun...@lists.ximian.com] On Behalf Of Robert Jordan Sent: 11 February 2009 15:24 To: mono-devel-list@lists.ximian.com Subject: Re: [Mono-dev] Patch for IntPtr bug russell....@realtimeworlds.com wrote: > I encountered a problem when casting a long to an IntPtr, which is > something we have ended up doing a lot (we want to keep binary assembly > compatibility between x86 and x64, only changing the native code on the > different architectures). We encountered a problem with Mono as there > has been a check introduced into the IntPtr constructor from a long, > this is checking the range of the long to ensure it is in range, > unfortunately the check is incorrect. A long can easily hold from > Int32.MinValue to UInt32.MaxValue (and not Int32.MaxValue as it > currently in there). > The patch is wrong, since casting a long > Int32.MaxValue to a 4 byte signed intptr is simply invalid. The current check in IntPtr.cs also matches MS.NET. Robert _______________________________________________ Mono-devel-list mailing list Mono-devel-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-devel-list ____________________________________________________________________ This email has been scanned by the MessageLabs Email Security System ____________________________________________________________________ DISCLAIMER This message and any attachments contain privileged and confidential information intended for the use of the addressee named above. If you are not the intended recipient of this message, you are hereby notified that any use, dissemination, distribution or reproduction of this message is prohibited. Please note that we cannot guarantee that this message or any attachment is virus free or that it has not been intercepted and amended. The views of the author may not necessarily reflect those of Realtime Worlds Ltd. Realtime Worlds Ltd is registered in Scotland, number 225628. Registered Office: 152 West Marketgait, Dundee, DD1 1NJ. _______________________________________________ Mono-devel-list mailing list Mono-devel-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-devel-list ____________________________________________________________________ This email has been scanned by the MessageLabs Email Security System ____________________________________________________________________ DISCLAIMER This message and any attachments contain privileged and confidential information intended for the use of the addressee named above. If you are not the intended recipient of this message, you are hereby notified that any use, dissemination, distribution or reproduction of this message is prohibited. Please note that we cannot guarantee that this message or any attachment is virus free or that it has not been intercepted and amended. The views of the author may not necessarily reflect those of Realtime Worlds Ltd. Realtime Worlds Ltd is registered in Scotland, number 225628. Registered Office: 152 West Marketgait, Dundee, DD1 1NJ. _______________________________________________ Mono-devel-list mailing list Mono-devel-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-devel-list