Disallow loading non-Explicit types with explicit field offsets #113500
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Tagging subscribers to this area: @mangod9 |
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Pull Request Overview
This PR removes support for explicit field offsets on non-explicit layout types by making the type loader throw a TypeLoadException when such offsets are detected.
- Added tests in AutoLayout and SequentialOffsets to validate that a TypeLoadException is thrown.
- Ensured both auto and sequential layout tests check for the disallowed feature.
Reviewed Changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/tests/Loader/classloader/AutoLayout/AutoLayout.cs | Adds a test to confirm that Auto-layout types with field offsets throw a TypeLoadException. |
| src/tests/Loader/classloader/SequentialLayout/Offsets/SequentialOffsets.cs | Adds a similar test for Sequential layout types with field offsets. |
src/tests/Loader/classloader/SequentialLayout/Offsets/SequentialOffsets.cs
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Pull Request Overview
This pull request introduces tests to verify that attempting to load non-explicit layout types with explicit field offsets now throws a TypeLoadException, enforcing the ECMA-335 specification.
- Added test in AutoLayout to ensure explicit field offsets are disallowed for auto-layout types.
- Added test in SequentialOffsets to ensure explicit field offsets are disallowed for sequential layout types.
Reviewed Changes
Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/tests/Loader/classloader/AutoLayout/AutoLayout.cs | Adds a test for Auto-layout types with explicit field offsets |
| src/tests/Loader/classloader/SequentialLayout/Offsets/SequentialOffsets.cs | Adds a test for Sequential layout types with explicit field offsets |
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This was referenced Mar 18, 2025
src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs
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jkotas
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Mar 19, 2025
| @@ -394,7 +394,8 @@ BEGIN | |||
| IDS_INVALID_REDIM "Illegal attempt to replace or redimension a fixed or locked SafeArray." | |||
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| IDS_INVALID_PINVOKE_CALLCONV "Unsupported unmanaged calling convention." | |||
| IDS_CLASSLOAD_NSTRUCT_EXPLICIT_OFFSET "Could not load type '%1' from assembly '%2' because field '%3' was not given an explicit offset." | |||
| IDS_CLASSLOAD_EXPSTRUCT_EXPLICIT_OFFSET "Could not load type '%1' from assembly '%2' because field '%3' was not given an explicit offset." | |||
| IDS_CLASSLOAD_STRUCT_EXPLICIT_OFFSET "Could not load type '%1' from assembly '%2' because field '%3' in a non-explicit type was given an explicit offset." | |||
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Suggested change
| IDS_CLASSLOAD_STRUCT_EXPLICIT_OFFSET "Could not load type '%1' from assembly '%2' because field '%3' in a non-explicit type was given an explicit offset." | |
| IDS_CLASSLOAD_STRUCT_EXPLICIT_OFFSET "Could not load type '%1' from assembly '%2' because field '%3' in was given an explicit offset, that is only allowed in types with explicit layout." |
"non-explicit type" is not an established term
| @@ -293,17 +293,37 @@ static bool CompareTypeLayout(MetadataType type1, MetadataType type2) | |||
| (layoutMetadata1.Size != layoutMetadata2.Size)) | |||
| return false; | |||
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| if ((explicitLayout) && !(layoutMetadata1.Offsets == null && layoutMetadata2.Offsets == null)) | |||
| if (explicitLayout) | |||
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We walk all fields on both types starting at line 209 in this file already - I would just add the check there so that we don't need to do this ugly compare-two-IEnumerables dance twice.
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LGTM other than the existing comments from others |
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Today, explicit field offsets on Auto-layout types are ignored, as are offsets on Sequential types that don't qualify for ManagedSequential (and as a result end up with Auto layout).
For Sequential layout, CoreCLR allows offsets to be specified. These "offsets" specify the sequencing order of the fields in sequential layout. This behavior is disallowed (you can't specify FieldOffset on a Sequential type) and unused by Roslyn and F# and C++/CLI. It's also illegal per the ECMA-335 spec (it specifically only allows FieldOffset rows for fields in an explicit layout type).
We had one IL regression test that validated that specifying offsets for a sequential type was ignored (so not testing the above feature).
Remove this unused feature and change the type loader to throw if a non-explicit layout type has offset information for its fields.