iOS apps not symbolicating in release mode

[jamescrosswell]

Description

Symbolication / source context for stack traces is missing in release mode on iOS.

This is due to a problem in the .NET SDK when building for Apple platforms in release mode. This issue has been reported to Microsoft and is being tracked in the .NET runtime repository.

If this issue affects your application, please:

1. Visit the .NET runtime issue
2. Add a reaction (👍) to indicate this affects you
3. Consider adding a comment describing your use case

This will help Microsoft prioritise the fix based on community impact.

Workarounds

Until the issue is resolved properly, symbolication on Apple platforms is only possible by disabling stripping. For example, by adding the following to your *.csproj file(s):

<PropertyGroup>
  <EnableAssemblyILStripping>false</EnableAssemblyILStripping>
</PropertyGroup>

Important Note: This may significantly increase the size of your application.

Links

• Minimal repro of the behaviour
• Discord conversation
• Tracking issue in the dotnet repository:
  • IsPortableCodeView false in stripped assemblies on iOS dotnet/runtime#118700

Further details (original issue report)

It looks like there's a mismatch in the Age field of the DebugID. For example, this is what is being uploaded to Sentry (portable PDB file):

sentry-cli debug-files check ./samples/Sentry.Samples.Maui/obj/Release/net9.0-ios18.0/iossimulator-arm64/Sentry.Samples.Maui.pdb
Debug Info File Check
  Type: portablepdb debug companion
  Contained debug identifiers:
    > Debug ID: 38b96763-ba6a-469d-08f6-03cdcd8e4657-c17c59f
      Arch:     unknown
  Contained debug information:
    > debug, sources
  Usable: yes

But in the event I'm seeing:

"debug_id":"38b96763-ba6a-469d-08f6-03cdcd8e4657-1","debug_file":"/Users/jamescrosswell/code/sentry-dotnet/samples/Sentry.Samples.Maui/obj/Release/net9.0-ios18.0/iossimulator-arm64/Sentry.Samples.Maui.pdb"

If I run sentry-cli debug-files find 38b96763-ba6a-469d-08f6-03cdcd8e4657-1, I see:

38b96763-ba6a-469d-08f6-03cdcd8e4657-1 /Users/jamescrosswell/code/sentry-dotnet/samples/Sentry.Samples.Maui/obj/Release/net9.0-ios18.0/iossimulator-arm64/stripped/Sentry.Samples.Maui.dll [pe]

So the PE header for the stripped assembly that is actually running on the device has an Age field of 1. However this is not a debug file (and can't be uploaded).

[linear]

NET-409 iOS apps not symbolicating in release mode

[devperson]

We have the same issue. Can anyone let us know any workaround for this issue?

[jamescrosswell]

What is suspicious is that we see the full debug id in Debug mode. So in Debug mode we get a debug_id like 3d6b32c9-2dec-4405-93a8-93588829a4f5-c0c54639 in the PE Header, but in Release mode somehow this gets transformed/stripped down to 3d6b32c9-2dec-4405-93a8-93588829a4f5-1 (but the full debug id with the signature/age field is included in the PDB that gets uploaded to Sentry).

In Sentry, this is where the debug_id gets read from the PE Header when capturing a stack trace:

sentry-dotnet/src/Sentry/Internal/Extensions/PEReaderExtensions.cs

Lines 49 to 62 in 24c159f

	// Specification:
	// https://github.com/dotnet/runtime/blob/main/docs/design/specs/PE-COFF.md#codeview-debug-directory-entry-type-2
	//
	// See also:
	// https://learn.microsoft.com/dotnet/csharp/language-reference/compiler-options/code-generation#debugtype
	//
	// Note: Matching PDB ID is stored in the #Pdb stream of the .pdb file.
	if (entry.IsPortableCodeView)
	{
	// Portable PDB Format
	// Version Major=any, Minor=0x504d
	debugId = $"{codeView.Guid}-{entry.Stamp:x8}";
	}

[jamescrosswell]

OK some progress. Actually line 61 above is not executing as expected. For some reason, entry.IsPortableCodeView is returning false and so this code gets executed instead:

sentry-dotnet/src/Sentry/Internal/Extensions/PEReaderExtensions.cs

Lines 65 to 67 in 24c159f

	// Full PDB Format (Windows only)
	// Version Major=0, Minor=0
	debugId = $"{codeView.Guid}-{codeView.Age}";

This should never happen on iOS...

The check happens here and it's failing because the MinorVersion == 0 (rather than PortablePdbVersions.PortableCodeViewVersionMagic):

This may be a bug in the runtime. I'll check with the Microsoft guys.

Potentially, in the short term, we could work around it by conditionally executing that if block only when running on Windows... and just assume Portable PDB everywhere else?

[jamescrosswell]

@devperson the debug directory entries appear to get modified during linking. As a temporary workaround, you could add an argument like /p:MtouchLink=SdkOnly when building your application. The application would be slightly larger as a result, but would then include enough information for Sentry to be able to correctly identify the PDB symbols associated with each module when symbolicating stack traces (at least for any code in your application... it may not be able to symbolicate code from the .NET SDK).