Evilness of unsafe c#

[Kryso]

I haven't seen much examples of unsafe code on these forums and I think I've read somewhere here that it's evil, however I can't really figure out why. I'm now experimenting with directx in my tool and unsafe code is actually helping me a lot. So far the only thing I have found against using it is harder debugging, however I don't know what exactly it does under the hood.

For example this:

fixed ( Line* pBuffer = lines )
    device.DrawPrimitiveUP( D3DPrimitiveType.LINELIST, lines.Length, pBuffer, sizeof( Line ) / 2 );

looks much simpler than it's safe alternative wich would probably look like this:

int size = Marshal.SizeOf( typeof( Line ) );
IntPtr pMemory = Marshal.AllocHGlobal( size * lines.Length );
try {
    for ( int i = 0; i < lines.Length; i++ )
        Marshal.StructureToPtr( lines[ i ], pMemory.Offset( i * size ), false );

    device.DrawPrimitiveUP( D3DPrimitiveType.LINELIST, lines.Length, pMemory, size / 2 );
}
finally {
    Marshal.FreeHGlobal( pMemory );
}

this is probably wrong forum, but I'm afraid nobody reads the c# section so sorry about that

[kynox]

What the jesus? lines.ToArray()

[Kryso]

variable "lines" = array of type "Line"
type "Line" = 2 vertexes

So you are suggesting put into DrawPrimitiveUP delegate "ref Line[]" or better "ref Vertex[]"? Well that would work, but it would limit me to only one vertex type. I'm probably not gonna use more that one for my current needs, but still I would like it to be more generic

[kynox]

variable "lines" = array of type "Line"
type "Line" = 2 vertexes

So you are suggesting put into DrawPrimitiveUP delegate "ref Line[]" or better "ref Vertex[]"? Well that would work, but it would limit me to only one vertex type. I'm probably not gonna use more that one for my current needs, but still I would like it to be more generic

What you're doing is just overcomplicating things. The function is generic..

[amadmonk]

Well, this code sample may have been silly, but the general point that unsafe C# often simplifies things (by not having to deal with GC, by allowing you to directly deref a pointer to a struct, etc.) is still valid

I guess I just assumed everyone knew that...

[flo8464]

Wouldn't C++/CLI be a better solution for you if you like unsafe C#?

[Kryso]

Amadmonk: thanks, thats exactly what I wanted to hear

However I still can't figure out why my example is bad. Lets say I want to make wrapper for IDirect3DDevice9. How can I define safe delegate that accepts different struct arrays as one parameter without Marshal.StructureToPtr? For example my vertex can look both like this:

struct VertexXYZD {
    Vector3 vector;
    Color diffuse;
}

and this:

struct VertexXYZND {
    Vector3 vector;
    Vector3 normal;
    Color diffuse;
}

I was thinking about using System.Array type, but that can be marshalled only into SafeArray and I need LPArray.. so what em I missing?


flo8464: maybe, but this looks like fun actually

[Apoc]

You would still need to 'decorate' the struct with the marshal attributes. .NET still needs to be aware of how the struct is mapped to memory to be able to dereference it from a pointer.

[vulcanaoc]

Wouldn't C++/CLI be a better solution for you if you like unsafe C#?

C++/CLI is a pretty ugly thing.

[amadmonk]

C++/CLI is a pretty ugly thing.

I'm actually slowly learning to love it.

I know Cypher will laugh, but the truth is that for some tasks, it's the best way to bind native and .Net stuff together.

Purist C++ coders will hate it, of course, and there are parts that I'm not fond of, but... it's not that bad

[Cypher]

I'm actually slowly learning to love it.

I know Cypher will laugh, but the truth is that for some tasks, it's the best way to bind native and .Net stuff together.

Purist C++ coders will hate it, of course, and there are parts that I'm not fond of, but... it's not that bad

Oh, I totally agree it's the most appropriate language for certain tasks. It's just one of those things you love to hate though.

[MaiN]

Oh, I totally agree it's the most appropriate language for certain tasks. It's just one of those things you love to hate though.

Cypher (Chazwazza) @ MMOwned: The fact that you have to use C++/CLI to wrap C++ code to make it available to C#
Cypher (Chazwazza) @ MMOwned: is a mess
Cypher (Chazwazza) @ MMOwned: that's just awful
Cypher (Chazwazza) @ MMOwned: so
Cypher (Chazwazza) @ MMOwned: fail

Cypher to me at wrapping Recast and Detour with C++/CLI.

[Cypher]

Cypher to me at wrapping Recast and Detour with C++/CLI.

WHOOOSH!!!!1111oneoneone