Cannot debug dotnet Docker amd64 container on host OSX M2

[eitanbehar]

Type: Bug

1. On a MacBook Pro OSX M2
2. Follow guide from VSCode documentation:
   https://code.visualstudio.com/docs/containers/debug-netcore
3. Change base image to platform linux amd64
   FROM --platform=linux/amd64 mcr.microsoft.com/dotnet/runtime:6.0

Extension version: 1.25.2
VS Code version: Code 1.80.0 (Universal) (660393deaaa6d1996740ff4880f1bad43768c814, 2023-07-04T13:39:33.766Z)
OS version: Darwin arm64 22.5.0
Modes:

System Info

Item	Value
CPUs	Apple M2 Pro (12 x 24)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	1, 2, 2
Memory (System)	32.00GB (0.15GB free)
Process Argv
Screen Reader	no
VM	0%

[alexyaang]

@eitanbehar What is the error message you're seeing?

[eitanbehar]

@alexyaang there is no error (at least I don't see it), the container runs, but the breakpoint is faded out with message that "no symbols have been loaded"
there is a warning: "WARNING: The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
Note that if I remove --platform=linux/amd64 then it will run/debug smoothly.
If it helps, I can provide a full working example

[bwateratmsft]

It's possible that an Apple Silicon Macbook is not capable of debugging an amd64 container. We should investigate @alexyaang.

[alexyaang]

@eitanbehar Thanks for providing more info! I'll do some investigating since I have a M1 Mac as well. 👍

@bwateratmsft That is a possibility. time to try it myself

[eitanbehar]

@alexyaang thanks for looking into this, please, let me know if more details are needed.

[alexyaang]

@eitanbehar I was able to replicate this issue and I think I know why. 😄 Can you drop the contents of your launch.json, tasks.json, and your Dockerfile? And to confirm, your project is targeting .NET 6, correct?

[eitanbehar]

@alexyaang sure, adding the whole project for better share
https://github.com/eitanbehar/docker-samples/tree/main/httpListener

[alexyaang]

@eitanbehar After further investigation, it seems that the core issue lies in the inability for our debuggers to debug an amd64 container on an arm64 machine. This explains why, when you remove the --platform=linux/amd64 flag, debugging works as expected.

Without the --platform flag, Docker automatically determines the platform based on the architecture and settings of your computer. In your case, it defaults to linux/arm64, allowing you to successfully debug because you are on an arm64 machine. Consequently, this appears to be a debugger-related problem. I'm going to mark this as a duplicate of #2884.

Like you mentioned, removing the --platform=linux/amd64 flag will fix your issue (if you debug a arm64 container). But unfortunately, I'm not aware of a good solution to debug an amd64 .NET container on an arm64 machine currently.

Thank you for your cooperation and bringing this to our attention :)

[eitanbehar]

@alexyaang thanks your efforts on this. So if I understand correctly, this scenario is not currently supported, do you happen to know if there is a plan to address it in a near future. I am not looking for a commitment, just your gut feelings on this.
Btw, I found this note in the release notes for net7, which might be related:
".NET 7 is not supported being run (emulated) via QEMU. QEMU is used, for example, to emulate Arm64 containers on x64, and vice versa."
https://github.com/dotnet/core/blob/main/release-notes/7.0/supported-os.md#qemu
Thanks again, Eitan

[alexyaang]

@eitanbehar Your understanding is correct. I believe this scenario is not supported in .NET 6 or .NET 7.

However, progress is being made in .NET 8 :) dotnet/dotnet-docker#4388 (comment)

[bwateratmsft]

I'll close this as a dupe of #2884. Hopefully this becomes available soon!