dotnet/runtime

`process.MainModule` throws `Win32Exception` instead of `InvalidOperationException` when process has exited in some cases

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#105090 opened on Jul 18, 2024

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area-System.Diagnostics.Processdocumentationhelp wanted

Description

Description

Accessing MainModule after process exit throws an exception that doesn't match the documentation. The code should either be changed to detect that case or the docs should be changed.

Reproduction Steps

using Process process = Process.GetProcessById(someId);
_ = process.Handle;
process.WaitForExit();
Console.WriteLine(process.ExitCode);
Console.WriteLine(process.MainModule?.FileName ?? "null");

Expected behavior

Throws InvalidOperationException as per docs.

Actual behavior

Throws:

Unhandled exception. System.ComponentModel.Win32Exception (299): Only part of a ReadProcessMemory or WriteProcessMemory request was completed.
   at System.Diagnostics.NtProcessManager.EnumProcessModulesUntilSuccess(SafeProcessHandle, IntPtr[], Int32, Int32&, Int32) + 0x91
   at System.Diagnostics.NtProcessManager.GetModules(Int32, Boolean) + 0x110
   at System.Diagnostics.NtProcessManager.GetFirstModule(Int32) + 0xf

Regression?

Not sure.

Known Workarounds

No response

Configuration

Windows 10.0.19045 X64 .NET 9

Other information

No response

Contributor guide

Tech stack
csharp
Domain
apibackend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C#Win32 API
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Examine the stack trace referencing NtProcessManager.EnumProcessModulesUntilSuccess. The method likely throws Win32Exception when the process has exited. To fix, add a check for process exit before retrieving modules and throw InvalidOperationException as documented. Consider consulting the Windows API documentation for ReadProcessMemory behavior on exited processes.