[Proposal] Add Support For Pointers

[AzureSky12]

One of the things I'm sad VB does not have is support for pointers. I do plenty of high performance stuff in VB and it's pain to have to go and make a C# Class Library to plug into my projects just to be able handle memory-related stuff I often need to do.

Please can we have pointers in VB? That would be awesome!

[rolfbjarne]

This adds a lot of complexity for something that's IMHO not useful for most developers.

You can also work around it in VB by using the Marshal class - Marshal.ReadIntPtr, etc. (although the code admittedly turns out quite ugly). Also it's probably not as performant as C# unsafe, since I'm not sure how much the JIT is able to optimize it.

[Bill-McC]

I like the idea of pointers, but have less and less use for them these days , declining alongside the amount of pinvoke code I write ;)
So the question is the cost/benefit. I think I'd rather see work done to allow C# classes/partial classes inside a VB project; having the C# compiler a service the vb one calls on. So for the stuff you have to use C#, it'd be a much simpler experience. The big plus is you'd get to use all C# features that VB might be missing in the future.

[AzureSky12]

How do I add the Discussion label to my OP? I see it's meant to have a Discussion label. (I'm new to Github so not used to this.)

[AdamSpeight2008]

@AzureSky12 Only team member can add labels. See #8

[AdamSpeight2008]

Far as I know partial works across languages, I think you just have to make sure the namespaces match.

[AzureSky12]

@rolfbjarne Thanks for the Marshal.ReadIntPtr suggestion. I don't think I've tried that one before, I may have though, don't recall.

Hm, does it really make things on the back end that much more complex? I wouldn't have imaged so but then again I don't work on the back end so I wouldn't know, LOL.

[AzureSky12]

@Bill-McC Makes sense, Partial classes is a good idea.

[AzureSky12]

I still would love to see VB have support for pointers. I would like VB to be a first class language. Why settle for less than first class? (Ok, I see I may even have an unintended pun in there, LOL.)

[craigajohnson]

Partial classes as per @Bill-McC in the same project would be extremely excellent.

[rskar-git]

Pointers are powerful, on that I agree, but they are so troublesome in practice that one really should avoid making direct use of them. Even in C++, the usual paradigm is to make use of references, "smart" pointers, STL and Boost rather than ("raw") pointers whenever possible (see e.g. http://softwareengineering.stackexchange.com/questions/56935/why-are-pointers-not-recommended-when-coding-with-c, https://www.meetingcpp.com/index.php/br/items/cpp-future-and-the-pointer.html).

In the case of VB, I would prefer patterns/features in the language that the compiler can recognize and optimize on, such as it does for the With statement today. (BTW, has anyone checked out my proposal for Dim ByRef yet?)

For any regular situation that would benefit from pointer arithmetic, that should be something in the Framework. For the truly novel ones, there's no shame in reaching for "unsafe" C# or C/C++.

Finally, in this day and age of large CPU caches (see "CPU Caches and Why You Care" by Scott Meyers), branch predictions, hyper-threading etc., and the continuing bane of buffer overruns and memory leaks, we should be super trepidacious about pointers and pointer arithmetic. Usually, the more of that we can leave to the compiler, the better.

[TrendyTim]

@Bill-McC i was thinking the same thing.

Then when i started to reply i thought (sorry if this goes overboard) not only just [partial] classes, but even abandoning the whole c# / vb / f# project artificial separation, let anyone add any language file to any project and just have it work

Even better would be

Public Class TestClass
Private vbVar as String
#Language CS
  public static void Main()
   {
      vbVar = "From C#";
     MoreVBCode();
   }
#End Language
Sub MoreVBCode()
End Sub
End Class

Though i know there would be limitations (and perhaps only allowed in a .dotnet file instead of vb and cs files, although then you'd either need to specify the default language in some way), and i wouldn't expect to be able to switch languages in the middle of a method, with those limitations it could kinda be like an inline partial class so the compiler could handle it like that.

Although i have no idea how feasible that is. At the very least intermixing CS files and VB files in the same project would be a great start, and save me from having to have C# satellite assemblies .

Then we can truly be a unified platform, and languages can focus on their strengths without the other side being left out of nice features (not to say that lots of features shouldn't be cross implemented, because they should).

[Bill-McC]

@TrendyTim Although that'd be cool, it'd add an extra level of complexity, you'd have issues with exposing code file information to the code block such as namespaces, using vs imports. It could turn out that it is not that complex, but I'd set the target for partial classes, thus minimizing the metadata needed for each compiler. It'd probably make the code editing experience better as well.

[xieguigang]

Pointer in the C language can be simulated using System Marshal API in visualBasic.
For example, here is the memory pointer example in Visualbasic for processing the bitmap image in fast speed:

Image/Bitmap/BitmapScale.vb#L109

Dim byts As Marshal.Byte = rgbValues

 ' Set every third value to 255. A 24bpp bitmap will binarization.  
Do While Not rgbValues.NullEnd(3)
    ' Get the red channel
    iR = rgbValues(2)
    ' Get the green channel
    iG = rgbValues(1)
    ' Get the blue channel
    iB = rgbValues(0)
    ' If the gray value more than threshold and then set a white pixel.
    If (iR + iG + iB) / 3 > 100 Then
        ' White pixel
        byts(2) = 255
        byts(1) = 255
        byts(0) = 255
    Else
        ' Black pixel
        byts(2) = 0
        byts(1) = 0
        byts(0) = 0
    End If

    ' Move forward the memory pointer by step 4 bytes
    byts += style
Loop

[AnthonyDGreen]

Could you be more explicit about the high performance "stuff" and where pointers are giving you better performance? Is it just optimizing out array bounds checks?