.NET Core 9 Debugging Crashed (coredump generated)

[JMS-1]

Type: Bug

1. Create a new .NET 9 (Fedora 42, SDK 9.0.106, NETCore 9.0.5) console application dotnet new console -o tcpcrash.
2. Replace Program.cs with the code below
3. Make sure no TCP server is listening on port 59590 on localhost
4. dotnet run produces outputs ups and done as expected
5. Open the project with VSCode via code tcpcrash
6. Start debugging with F5 with a breakpoint on line 20 (throw IOException)
7. Program will start and debugger will immediately stop on line 20
8. Single Step Over
9. Debugging stops at once, no output generated
10. coredumpctl show a core dump BUT the app is STILL running

There is no problem when line 15 is replaced with await task1 - an exception "connection refused" will be generated. In principle this is expected since WhenAny will always run to completion. But crashing the debugger strongly feels like a bug in the debugging system.

The code is the core extract from here but obviously not connected to the ScpiNet package.

using System.Net.Sockets;

internal class Program
{
    private static async Task Main(string[] args)
    {
        var client = new TcpClient();
        var cancel = new CancellationTokenSource();

        try
        {
            var task1 = client.ConnectAsync("localhost", 59590);
            var task2 = Task.Delay(5000, cancel.Token);

            await Task.WhenAny(task1, task2);

            if (task2.IsCompleted) throw new TimeoutException("timed out");

            if (!client.Connected)
                throw new IOException("ups");
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }

        Console.WriteLine("done");
    }
}

VS Code version: Code 1.100.2 (848b80a, 2025-05-14T21:47:40.416Z)
OS version: Linux x64 6.14.6-300.fc42.x86_64
Modes:

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-14700 (28 x 1619)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: disabled_software vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: disabled_off webnn: disabled_off
Load (avg)	4, 3, 3
Memory (System)	31.14GB (9.30GB free)
Process Argv	--crash-reporter-id 3d6d6927-c0e6-47df-b680-669922c8e8fc
Screen Reader	no
VM	0%
DESKTOP_SESSION	cinnamon
XDG_CURRENT_DESKTOP	X-Cinnamon
XDG_SESSION_DESKTOP	cinnamon
XDG_SESSION_TYPE	x11

Extensions (113)

Extension	Author (truncated)	Version
vscode-openapi	42C	4.34.0
vscode-css-formatter	aes	1.0.2
nugetpackagemanagergui	ali	2.1.1
tsl-problem-matcher	amo	0.6.2
ng-template	Ang	20.0.1
vscode-apollo	apo	2.5.6
spellright	ban	3.0.142
vscode-django	bat	1.15.0
markdown-mermaid	bie	1.28.0
project-templates	can	1.2.0
path-intellisense	chr	2.10.0
vscode-css-modules	cli	0.5.4
gitignore	cod	0.10.0
doxdocgen	csc	1.4.0
vscode-eslint	dba	3.0.10
python-environment-manager	don	1.2.7
python-extension-pack	don	1.7.0
xml	Dot	2.5.1
eslint-disable-snippets	drK	1.4.1
vscode-wasm	dts	1.4.1
gitlens	eam	17.1.1
EditorConfig	Edi	0.17.2
prettier-vscode	esb	11.0.0
vscode-solution-explorer	fer	0.9.1
opensslutils	ffa	1.1.1
nunit-test-runner	For	0.3.10
auto-close-tag	for	0.5.15
auto-rename-tag	for	0.1.10
code-runner	for	0.12.2
dotnet-test-explorer	for	0.7.8
vscode-github-actions	git	0.27.1
vscode-test-explorer	hbe	2.22.1
ilspy-vscode	ics	0.20.0
plantuml	jeb	2.18.1
better-cpp-syntax	jef	1.27.1
vscode-nuget-package-manager	jmr	1.1.6
ghdl-interface	joh	1.1.2
cmake-language-support-vscode	jos	0.0.9
awesometypescriptproblemmatcher	Jua	0.3.0
docomment	k--	1.0.0
vsc-python-indent	Kev	1.21.0
unity-code-snippets	kle	2.4.0
l13-diff	L13	1.3.9
karma-test-explorer	luc	0.8.2
template-string-converter	meg	0.6.1
import-sorter	mik	3.3.1
mongodb-vscode	mon	1.13.2
vscode-android-webview-debug	mpo	1.2.3
vscode-scss	mrm	0.10.0
csdevkit	ms-	1.19.63
csharp	ms-	2.76.27
vscode-dotnet-runtime	ms-	2.3.5
vscodeintellicode-csharp	ms-	2.2.3
data-workspace-vscode	ms-	0.6.2
mssql	ms-	1.32.0
sql-bindings-vscode	ms-	0.4.1
sql-database-projects-vscode	ms-	1.5.2
debugpy	ms-	2025.8.0
isort	ms-	2025.0.0
python	ms-	2025.6.1
vscode-pylance	ms-	2025.5.1
remote-containers	ms-	0.413.0
remote-ssh	ms-	0.120.0
remote-ssh-edit	ms-	0.87.0
remote-wsl	ms-	0.99.0
cmake-tools	ms-	1.20.53
cpptools	ms-	1.25.3
cpptools-extension-pack	ms-	1.3.1
hexeditor	ms-	1.11.1
makefile-tools	ms-	0.12.17
powershell	ms-	2025.0.0
remote-explorer	ms-	0.5.0
test-adapter-converter	ms-	0.2.1
vscode-serial-monitor	ms-	0.13.1
vsliveshare	ms-	1.0.5948
vscode-json-editor	nic	0.3.0
gulptasks	nic	1.3.1
autodocstring	njp	0.6.1
oxc-vscode	oxc	0.16.12
vscode-print	pdc	1.4.1
vscode-versionlens	pfl	1.22.2
csharp-to-plantuml	pie	1.4.0
platformio-ide	pla	3.3.4
awesome-vhdl	puo	0.0.1
java	red	1.42.0
vscode-commons	red	0.0.6
vscode-xml	red	0.29.0
vscode-yaml	red	1.18.0
vscode-sort-json	ric	1.20.0
LiveServer	rit	5.7.9
svg-preview	Sim	2.8.3
move-ts	str	1.12.0
iconfont-preview	stx	0.0.5
vscode-stylelint	sty	1.5.0
sass-indented	syl	1.8.33
json-schema-validator	tbe	0.1.0
unity-tools	Tob	1.2.12
pdf	tom	1.2.2
qtvsctools	ton	0.11.0
vhdl-formatter	Vin	1.0.5
intellicode-api-usage-examples	Vis	0.2.9
vscodeintellicode	Vis	1.3.2
vstuc	vis	1.1.2
explorer	vit	1.18.1
vscode-boot-dev-pack	vmw	0.2.2
vscode-concourse	vmw	1.56.0
vscode-manifest-yaml	vmw	1.55.0
vscode-spring-boot	vmw	1.62.0
vscode-gradle	vsc	3.16.4
vscode-spring-initializr	vsc	0.11.2
vscode-icons	vsc	12.13.0
volar	Vue	2.2.10
jinja	who	0.0.8

(1 theme extensions excluded)

A/B Experiments

vsliv368:30146709
vspor879:30202332
vspor708:30202333
vspor363:30204092
vscod805:30301674
binariesv615:30325510
c4g48928:30535728
azure-dev_surveyone:30548225
vscrp:30673768
962ge761:30959799
h48ei257:31000450
pythontbext0:30879054
cppperfnew:31000557
dwnewjupyter:31046869
pythonrstrctxt:31112756
nativeloc1:31192215
5fd0e150:31155592
dwcopilot:31170013
6074i472:31201624
dwoutputs:31242946
customenabled:31248079
hdaa2157:31222309
copilot_t_ci:31222730
e5gg6876:31282496
pythoneinst12:31285622
bgtreat:31268568
4gafe986:31271826
c7cif404:31314491
996jf627:31283433
pythonrdcb7:31303018
usemplatestapi:31297334
0aa6g176:31307128
7bj51361:31289155
747dc170:31275177
pylancecolor:31314202
aj953862:31281341
generatesymbolt:31295002
convertfstringf:31295003
gendocf:31295004

[sandy081]

Please file the issue against the dot net extension you have installed.

[JMS-1]

Can you please tell me what you mean with that? All stuff installed as far as I can see just the latest available on Fedora 42. Where am I wrong?

[sandy081]

VS Code does not support debugging dot net project out of the box. You might have installed a dot net extension that would have added support for this. Please find the extension that you installed for dot net support and file the issue against that extension. Please let me know if that helps.