Add SIGKILL to PosixSignal enumeration#124256

Copilot · 2026-02-11T07:33:10Z

Description

Extends PosixSignal with SIGKILL = -11. SIGKILL cannot be caught or ignored per POSIX semantics - the OS enforces this naturally by throwing appropriate exceptions when registration is attempted.

Changes

Enumeration: Added PosixSignal.SIGKILL = -11 with [UnsupportedOSPlatform("windows")] and XML doc "Kill (cannot be caught or ignored)"
Ref assembly: Added SIGKILL = -11 entry with [UnsupportedOSPlatformAttribute("windows")]
Native layer: Updated pal_signal.{h,c} to map SIGKILL in GetPlatformSignalNumber and TryConvertSignalCodeToPosixSignal
OS-level validation: No explicit validation in managed code - the OS handles SIGKILL registration attempts naturally:
- Unix: OS throws IOException when trying to enable signal handling for SIGKILL
- Windows: Throws PlatformNotSupportedException (SIGKILL not in supported signals)
Tests: Added PosixSignal.SIGKILL to UninstallableSignals() on Unix; excluded SIGKILL from SupportedSignals, PosixSignalAsRawValues, and ProcessTests.SignalTestData() test data

Contributes to #123380

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

dotnet-policy-service · 2026-02-11T07:41:08Z

Tagging subscribers to this area: @dotnet/interop-contrib
See info in area-owners.md if you want to be subscribed.

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

adamsitnik

@copilot please address my feedback

...es/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.Unix.cs

@adamsitnik

Per feedback from @adamsitnik, moved SIGKILL validation from the Unix-specific Register method to the platform-agnostic Create method. The validation now checks both the SIGKILL enum value (-11) and the raw POSIX signal number (9), ensuring SIGKILL cannot be registered on any platform. Removed the s_sigkillNumber field as it's no longer needed. Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Copilot · 2026-02-11T08:21:53Z

@copilot please address my feedback

Feedback addressed in commit b421171. Moved SIGKILL validation from Unix-specific Register method to platform-agnostic Create method, and removed the s_sigkillNumber field.

Replaced magic number 9 with SIGKILL_POSIX_SIGNAL_NUMBER constant for better code clarity and maintainability. Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Updated comment to clarify that we check both PosixSignal.SIGKILL (-11) and raw signal number 9 cast to enum type (e.g., (PosixSignal)9). Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs

@jkotas

Per feedback from @jkotas and @adamsitnik: - Changed exception from ArgumentException to IOException to match OS behavior - Removed check for raw signal number (9) - let OS throw IOException naturally - Only check PosixSignal.SIGKILL enum value to provide better error message - Updated test to expect IOException instead of ArgumentException - Removed unused SIGKILL_POSIX_SIGNAL_NUMBER constant This avoids a breaking change where the exception type would differ for raw signal numbers vs enum values. Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs

adamsitnik

@copilot please address my feedback

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs

@jkotas

Per feedback from @jkotas and @adamsitnik: - Removed SIGKILL check from platform-agnostic Create method - Removed Arg_CannotRegisterHandlerForSIGKILL resource string - Let OS-specific Register methods throw naturally: - Unix: IOException from OS when trying to enable signal handling - Windows: PlatformNotSupportedException (SIGKILL not in switch) - Updated tests to be platform-specific: - Unix test expects IOException - Windows test expects PlatformNotSupportedException This allows the OS to handle validation naturally without adding extra checks that provide no value. Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Copilot · 2026-02-11T11:31:45Z

@copilot please address my feedback

Feedback addressed in commit fb5b0ac.

stephentoub · 2026-02-11T13:47:21Z

@adamsitnik, at the moment this doesn't add any benefit, right? It's only once we add the ability to send a PosixSignal that this becomes meaningful? And at that point we'll update consumers like Process.Kill() to use this instead of P/Invoking directly? (The correctness of the mapping / handling of this value would be easier if the sending ability were introduced first.)

Copilot

Pull request overview

This PR extends the System.Runtime.InteropServices.PosixSignal public API to include SIGKILL and wires it through the native System.Native signal mapping so it can be converted to/from platform signal numbers, along with updating unit tests to reflect SIGKILL’s non-registrable semantics.

Changes:

Added PosixSignal.SIGKILL = -11 (Windows-unsupported) to the public enum and reference assembly.
Updated System.Native PAL (pal_signal.h/.c) to map SIGKILL in both conversion directions.
Updated PosixSignalRegistration unit tests to ensure SIGKILL registration throws and to exclude SIGKILL from “supported/registrable” datasets.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/native/libs/System.Native/pal_signal.h	Adds `PosixSignalSIGKILL = -11` to the native enum.
src/native/libs/System.Native/pal_signal.c	Maps `SIGKILL` in `TryConvertSignalCodeToPosixSignal` and `SystemNative_GetPlatformSignalNumber`.
src/libraries/System.Runtime.InteropServices/ref/System.Runtime.InteropServices.cs	Adds `SIGKILL` to the reference assembly enum surface area.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignal.cs	Adds `SIGKILL` to the runtime enum with XML doc + platform annotation.
src/libraries/System.Runtime.InteropServices/tests/.../PosixSignalRegistrationTests.Unix.cs	Adds Unix-only SIGKILL throw test and removes SIGKILL from registrable test data.
src/libraries/System.Runtime.InteropServices/tests/.../PosixSignalRegistrationTests.Windows.cs	Adds Windows SIGKILL throw test.

...ropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Windows.cs

...nteropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Unix.cs

...ropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Windows.cs

@jkotas

Per @jkotas feedback: add PosixSignal.SIGKILL to UninstallableSignals() on Unix so it's covered by Create_UninstallableSignal_Throws, and delete the explicit Create_SIGKILL_Throws tests from both Unix and Windows files (the Windows test was redundant with Create_InvalidSignal_Throws). Also remove the now-unnecessary 'using System.IO;' directive from the Unix file. Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

jkotas · 2026-02-11T15:55:49Z

And at that point we'll update consumers like Process.Kill() to use this instead of P/Invoking directly?

The Process interop uses SIGKILL and SIGSTOP:

runtime/src/libraries/Common/src/Interop/Unix/System.Native/Interop.Kill.cs

Lines 14 to 15 in 7feb033

    
           SIGKILL = 9, 
        
           SIGSTOP = 19

While this can replace uses of SIGKILL, we do not have a SIGSTOP. Also, the hardcoded 19 for SIGSTOP Is non-portable. Should we add SIGSTOP (and SIGCONT for parity) to the public API too?

adamsitnik · 2026-02-11T15:56:45Z

@adamsitnik, at the moment this doesn't add any benefit, right? It's only once we add the ability to send a PosixSignal that this becomes meaningful? And at that point we'll update consumers like Process.Kill() to use this instead of P/Invoking directly? (The correctness of the mapping / handling of this value would be easier if the sending ability were introduced first.)

For me the main benefit is having the other upcoming PRs smaller and easier to review. Then we will just focus on sending the signals, not ensuring that existing APIs can't sign up for SIGKILL like in this PR.

I'll try to do better in upcoming PRs.

jkotas

LGTM (as an incremental step towards implementing full API proposal)

jkotas · 2026-02-11T15:58:46Z

For me the main benefit is having the other upcoming PRs smaller and easier to review

I personally prefer smaller PRs like this one (when it is well understood what we are working towards)

stephentoub · 2026-02-11T16:20:30Z

For me the main benefit is having the other upcoming PRs smaller and easier to review

I personally prefer smaller PRs like this one (when it is well understood what we are working towards)

I do as well, but I prefer it further when they're "complete". My preference would have been to first add the send API, which could be fully tested (and possibly used in various places). Then this PR would be able to actually validate that the signal mapping is working correctly by using that send API in a test to kill a child process, and could also be consumed in places like Process. It's still smaller, but it's more end-to-end.

That said, we can go ahead with this one.

jkotas · 2026-02-12T01:35:52Z

@copilot Failing test

Unhandled Exception:
System.IO.IOException: Invalid argument
   at Interop.ThrowExceptionForIoErrno(ErrorInfo errorInfo, String path, Boolean isDirError) in /_/src/libraries/Common/src/Interop/Unix/Interop.IOErrors.cs:line 16
   at Interop.ThrowIOExceptionForLastError() in /_/src/libraries/Common/src/Interop/Unix/Interop.IOErrors.cs:line 53
   at System.Runtime.InteropServices.PosixSignalRegistration.Register(PosixSignal signal, Action`1 handler) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.Unix.cs:line 47
   at System.Runtime.InteropServices.PosixSignalRegistration.Create(PosixSignal signal, Action`1 handler) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs:line 42
   at System.Diagnostics.Tests.ProcessTests.<>c.<TestCreateNewProcessGroup_HandlerReceivesExpectedSignal>b__6_0(String signalStr) in /_/src/libraries/System.Diagnostics.Process/tests/ProcessTests.cs:line 124
   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args) in /_/src/mono/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.Mono.cs:line 22
   at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr) in /_/src/libraries/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.cs:line 174

SIGKILL cannot be caught or ignored, so iterating all PosixSignal enum values to register handlers fails for SIGKILL with IOException. Skip it in the test data, consistent with how SIGKILL is excluded from SupportedSignals in PosixSignalRegistrationTests. Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot · 2026-02-12T01:40:04Z

@copilot Failing test
Unhandled Exception:

...

Fixed in commit 4813de4. ProcessTests.SignalTestData() iterates Enum.GetValues<PosixSignal>() which now includes SIGKILL. Added a skip for PosixSignal.SIGKILL since it cannot be caught or ignored.

adamsitnik · 2026-02-12T14:13:25Z

/ba-g the build failure is #124322, which got already fixed in main

Initial plan

8a90fc8

Copilot AI assigned Copilot and adamsitnik Feb 11, 2026

Copilot started work on behalf of adamsitnik February 11, 2026 07:33 View session

Add SIGKILL enumeration value and validation

2f34cf9

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

github-actions bot added the area-System.Runtime.InteropServices label Feb 11, 2026

Copilot AI and others added 2 commits February 11, 2026 07:58

Fix SIGKILL validation for raw signal values and exclude from test data

d319cb4

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Cache SIGKILL signal number to avoid repeated interop calls

f4a7d09

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Extend PosixSignal enumeration with SIGKILL value~~ Add SIGKILL to PosixSignal enumeration with registration validation Feb 11, 2026

Copilot AI requested a review from adamsitnik February 11, 2026 08:02

Copilot finished work on behalf of adamsitnik February 11, 2026 08:02

adamsitnik reviewed Feb 11, 2026

View reviewed changes

...es/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.Unix.cs Outdated Show resolved Hide resolved

Copilot started work on behalf of adamsitnik February 11, 2026 08:06 View session

Copilot AI and others added 2 commits February 11, 2026 08:23

Use named constant for SIGKILL raw signal number

db40541

Replaced magic number 9 with SIGKILL_POSIX_SIGNAL_NUMBER constant for better code clarity and maintainability. Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Clarify comment about SIGKILL validation checks

dc898bb

Updated comment to clarify that we check both PosixSignal.SIGKILL (-11) and raw signal number 9 cast to enum type (e.g., (PosixSignal)9). Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>

Copilot AI requested a review from adamsitnik February 11, 2026 08:26

Copilot finished work on behalf of adamsitnik February 11, 2026 08:26

jkotas reviewed Feb 11, 2026

View reviewed changes

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs Outdated Show resolved Hide resolved

Copilot started work on behalf of adamsitnik February 11, 2026 08:53 View session

Copilot finished work on behalf of adamsitnik February 11, 2026 09:00

jkotas reviewed Feb 11, 2026

View reviewed changes

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs Outdated Show resolved Hide resolved

adamsitnik reviewed Feb 11, 2026

View reviewed changes

...braries/System.Private.CoreLib/src/System/Runtime/InteropServices/PosixSignalRegistration.cs Outdated Show resolved Hide resolved

Copilot started work on behalf of adamsitnik February 11, 2026 11:25 View session

Copilot AI changed the title ~~Add SIGKILL to PosixSignal enumeration with registration validation~~ Add SIGKILL to PosixSignal enumeration Feb 11, 2026

Copilot AI reviewed Feb 11, 2026

View reviewed changes

...ropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Windows.cs Outdated Show resolved Hide resolved

jkotas reviewed Feb 11, 2026

View reviewed changes

...nteropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Unix.cs Outdated Show resolved Hide resolved

Copilot started work on behalf of jkotas February 11, 2026 15:07 View session

jkotas reviewed Feb 11, 2026

View reviewed changes

...ropServices.UnitTests/System/Runtime/InteropServices/PosixSignalRegistrationTests.Windows.cs Outdated Show resolved Hide resolved

Copilot AI requested a review from jkotas February 11, 2026 15:12

Copilot finished work on behalf of jkotas February 11, 2026 15:13

Copilot started work on behalf of jkotas February 11, 2026 15:14 View session

Copilot finished work on behalf of jkotas February 11, 2026 15:18

jkotas approved these changes Feb 11, 2026

View reviewed changes

This was referenced Feb 11, 2026

crossgen2 failing on Linux Arm32 intermittently #124007

Closed

System.Security.Cryptography.CryptographicException : m_safeCertContext is an invalid handle. #124279

Closed

Copilot started work on behalf of jkotas February 12, 2026 01:36 View session

Copilot AI requested a review from jkotas February 12, 2026 01:40

Copilot finished work on behalf of jkotas February 12, 2026 01:40

Merge branch 'main' into copilot/extend-posixsignal-enumeration

ca3aaa3

This was referenced Feb 12, 2026

"We stopped hearing from agent Azure Pipelines 32. Verify the agent machine is running and has a healthy network connection" dotnet/dnceng#1886

Open

Test failure: baseservices/exceptions/stackoverflow/stackoverflowtester/stackoverflowtester.cmd #110173

Open

adamsitnik merged commit 2690e0f into main Feb 12, 2026
160 of 168 checks passed

adamsitnik deleted the copilot/extend-posixsignal-enumeration branch February 12, 2026 14:17

dotnet-maestro bot mentioned this pull request Feb 13, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#4839

Merged

Comments

Conversation

Copilot AI commented Feb 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Changes

Uh oh!

dotnet-policy-service bot commented Feb 11, 2026

Uh oh!

adamsitnik left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI commented Feb 11, 2026

Uh oh!

Uh oh!

Uh oh!

adamsitnik left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI commented Feb 11, 2026

Uh oh!

stephentoub commented Feb 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

jkotas commented Feb 11, 2026

Uh oh!

adamsitnik commented Feb 11, 2026

Uh oh!

jkotas left a comment

Choose a reason for hiding this comment

Uh oh!

jkotas commented Feb 11, 2026

Uh oh!

stephentoub commented Feb 11, 2026

Uh oh!

jkotas commented Feb 12, 2026

Uh oh!

Copilot AI commented Feb 12, 2026

Uh oh!

adamsitnik commented Feb 12, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Copilot AI commented Feb 11, 2026 •

edited

Loading

stephentoub commented Feb 11, 2026 •

edited

Loading