Forward declarations and #pragma managed/unmanaged

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Gustavo L. Fabro - 29 Jun 2005 19:13 GMT

Greetings!

Going directly to the point:

myclass.h:
//--------------------------------------

#pragma managed

//Forward declaration
class AnotherClass;

#pragma unmanaged

class MyClass
{
public:
void func1(AnotherClass* ptr);
}

Will this '#pragma managed' before 'class AnotherClass' have any effect at
all on my native class? I know the forwad declaration only puts the symbol's
name under the symbols table, but I was wondering if, being defined under
'managed' setting, this symbol would have any thunking layers or anything
like that that would make it's access slower.

Thanks,

Fabro

Reply to this Message

Carl Daniel [VC++ MVP] - 29 Jun 2005 21:02 GMT

> Greetings!
>
[quoted text clipped - 22 lines]
> thunking layers or anything like that that would make it's access
> slower.

Based on a very simply experiment, it doesn't appear to make any difference.
What matters is whether #pragma managed is in effect where the class
definition appears.

<code>
#pragma managed

//Forward declaration
class AnotherClass;

#pragma unmanaged

class MyClass
{
public:
void func1(AnotherClass* ptr) {}
};

#pragma unmanaged // 1

class AnotherClass
{
public:
void f() {}
};
</code>

If the line at //1 is #pragma unmanaged, the resulting .obj looks identical
to that produced if // 1 is deleted. It // 1 is #pragma managed,
AnotherClass::f() is emitted as managed code.

-cd

Reply to this Message

Gustavo L. Fabro - 01 Jul 2005 14:42 GMT

Hmmm

I took your idea and compiled these files

#1

#pragma managed
class AnotherClass;
#pragma unmanaged

class MyClass
{
public:
void func1(AnotherClass* ptr);
}

#2

#pragma unmanaged
class AnotherClass;
#pragma unmanaged

class MyClass
{
public:
void func1(AnotherClass* ptr);
}

The obj files have the same size but are different. But that doesn't tell
*me* much, because If I compile the same file twice, different (binary
speaking) obj files will be created too.

Fabro

Reply to this Message

Carl Daniel [VC++ MVP] - 01 Jul 2005 15:08 GMT

> Hmmm
>
[quoted text clipped - 28 lines]
> (binary
> speaking) obj files will be created too.

Use dumpbin /all on the .OBJ files to see the internals. I didn't do a very
thorough examination, but at the level I did look, it appeared that no
significant changes to the file were made. In your example, there's no code
being generated at all, so I think you need to embelish the test case just a
bit to make it meaningful.

-cd

Reply to this Message

Forward declarations and #pragma managed/unmanaged

Free Magazines