[Mono-list] Mono/.NET delegate incompatibility

[J. Perkins]

I am using a delegate to pass a function pointer into a unmanaged DLL.
Under Linux/Mono everything works fine. Under Windows/.NET, my callback
function signature must look like this:

void (__stdcall *func)(int);

But Windows/Mono seems to want:

void (*func)(int);

Changing the signature will cause the other CLR to corrupt the stack.

Jason
379

[Tum]

I guess the default calling convention in mono is cdecl. According to
MSDN, the default calling convention for dllimport should be stdcall
(which IMHO really only makes sense on windows).

You could try setting the CallingConvention property on the DllImport to
cdecl.

e.g.

[DllImport("mydll.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern void myfunc(int x);

^Tum

-----Original Message-----

On

Behalf Of J. Perkins
Sent: Thursday, 19 December 2002 9:24 a.m.
To: Mono-L
Subject: [Mono-list] Mono/.NET delegate incompatibility
I am using a delegate to pass a function pointer into a unmanaged DLL.
Under Linux/Mono everything works fine. Under Windows/.NET, my

callback

void (__stdcall *func)(int);
void (*func)(int);
Changing the signature will cause the other CLR to corrupt the stack.
Jason
379
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http://lists.ximian.com/mailman/listinfo/mono-list

[J. Perkins]

This is a good workaround. Thanks!

Jason
379

Post by Tum
I guess the default calling convention in mono is cdecl. According to
MSDN, the default calling convention for dllimport should be stdcall
(which IMHO really only makes sense on windows).
You could try setting the CallingConvention property on the DllImport to
cdecl.
e.g.
[DllImport("mydll.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern void myfunc(int x);

[J. Perkins]

Hang on a minute, I answered this too soon. I'm not talking about
calling a DLL function. [DllImport] works just fine on both Windows and
Linux. I am talking about a callback function, from unmanaged -> managed
code. That is, a C# delegate passed to and called from unmanaged code
via a function pointer. Here's a usenet thread on the subject:

http://makeashorterlink.com/?C417214D2

The problem described in this thread is reversed for Mono: the callback
must use the cdecl convention. Because of this, there is no way to write
a C function that can call a delegate under both .NET and Mono. If I do
this:

int SomeCFunction(int (__stdcall *callback)(int, int, int))
{ return callback(1,2,3); }

...it will corrupt the stack when run under Mono on Windows. If I use
cdecl instead:

int SomeCFunction(int (*callback)(int, int, int))
{ return callback(1,2,3); }

...it will corrupt the stack when run under .NET. Maybe I'm missing
something (quite possible), but it appears that Mono must use __stdcall
for delegates on Windows.

I'll give you guys a chance to sanity check my rambling. If it holds up
I will file a bug.

Jason
379

Post by Tum
I guess the default calling convention in mono is cdecl. According to
MSDN, the default calling convention for dllimport should be stdcall
(which IMHO really only makes sense on windows).
You could try setting the CallingConvention property on the DllImport to
cdecl.