ILVerify fails assemblies that use Span<T> and stackalloc

[defufna]

Description

Following code fails ILVerify verification:

Span<byte> buffer = stackalloc byte[16];

It fails with "Instruction cannot be verified.", but stackalloc with Span should be safe?

Reproduction Steps

1. Build a dll that contains mentioned code.
2. Run ILVerify on it

Expected behavior

Code passes verification

Actual behavior

Code fails verification with "Instruction cannot be verified." message.

Regression?

This is not a regression...

Known Workarounds

No response

Configuration

No response

Other information

No response

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Issue Details

---

Description

Following code fails ILVerify verification:

Span<byte> buffer = stackalloc byte[16];

It fails with "Instruction cannot be verified.", but stackalloc with Span should be safe?

Reproduction Steps

1. Build a dll that contains mentioned code.
2. Run ILVerify on it

Expected behavior

Code passes verification

Actual behavior

Code fails verification with "Instruction cannot be verified." message.

Regression?

This is not a regression...

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	defufna
Assignees:	-
Labels:	area-ILVerification
Milestone:	-

[teo-tsirpanis]

The concept of unsafe in C# and the concept of "unverifiable" in ECMA-335 are not the same. There are code constructs like stackalloc on spans that C# thinks is safe, but the verifier thinks it isn't.

[MichalPetryka]

See #37391.

[defufna]

I was afraid this might be the case @teo-tsirpanis... It's a pitty... Is there somewhere a list with other examples of safe C# code producing unverifiable IL ?

[JulieLeeMSFT]

@TIHan PTAL.