Marshalling `bool' .NET type to a unsigned char C type

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Emmanuel Stapf - 06 Dec 2003 00:56 GMT

Hi,

I have the following C code generated in `test.dll':

__declspec(dllexport) unsigned char __stdcall test (int i, int j)
{
return (unsigned char) ((i & j) == j);
}

In the .NET side I map it into:

.method public hidebysig static pinvokeimpl("test.dll" ansi)
bool test ([in] int32 i,
[in] int32 j) cil managed preservesig
{
}

However I've noticed that if my C code is compiled with all optimizations (-Ox)
then on the .NET side for the value i=0x6cf0000 and j=0x1000000, I get a true
value where I should get a false. If I don't have the -Ox flag then it works
properly.

I think that is possibly due to the marshalling of `bool' but I'm not sure. If
it is what should I do so that this above code works properly?

Thanks,
Manu

Reply to this Message

Mattias Sj?gren - 06 Dec 2003 01:28 GMT

Emmanuel,

>I think that is possibly due to the marshalling of `bool' but I'm not sure. If
>it is what should I do so that this above code works properly?

Make it

... bool marshal(int8) test( ...

Without the marshal modifier, the runtime expects a 32-bit Win32 BOOL
return value.

Mattias

Signature

Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

Reply to this Message

Emmanuel Stapf - 06 Dec 2003 03:03 GMT

> Make it
>
> ... bool marshal(int8) test( ...
>
> Without the marshal modifier, the runtime expects a 32-bit Win32 BOOL
> return value.

Does it make the operation faster?

Manu

Reply to this Message

Emmanuel Stapf - 09 Dec 2003 18:58 GMT

I've added a marshaller modifier for bool on my parameters too. I've noticed
something strange, if I pass a False value to my pinvoke, the C calls receives a
value of 0x01 and not 0x00 as I expected? I'm I doing something wrong?

My pinvoke is defined as:

.method public hidebysig static pinvokeimpl("libcursor.dll" ansi)
void Fdui0ly([in] native int hwnd,
[in] int32 bar_flag,
[in] bool marshal( int8) show_flag) cil managed
preservesig
{
)

And on the call site in .NET I have something like:

.method public hidebysig newslot virtual
instance void my_call([in] native int hwnd,
[in] int32 bar_flag) cil managed
{
// Code size 9 (0x9)
.maxstack 8
IL_0000: ldarg.1
IL_0001: ldarg.2
IL_0002: ldc.i4 0
IL_0003: call void MyClass::Fdui0ly(native int, int32, bool)
IL_0008: ret
} // end of method WelWindow::CwinShowScrollBar

Manu

Reply to this Message

Mattias Sj?gren - 10 Dec 2003 00:46 GMT

Emmanuel,

>Does it make the operation faster?

I don't know, I haven't done any perf testing.

>I've added a marshaller modifier for bool on my parameters too. I've noticed
>something strange, if I pass a False value to my pinvoke, the C calls receives a
>value of 0x01 and not 0x00 as I expected? I'm I doing something wrong?

I think this is a runtime bug, but I can't remember the exact details.
It seems to work correctly in Whidbey though.

But for parameters, since the unsigned char still occupies 32 bits on
the stack, I believe you might as well use the default marshaling and
leave out marshal(int8).

Mattias

Signature

Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

Reply to this Message

Marshalling `bool' .NET type to a unsigned char C type

Free Magazines