Codegen single-non-ZST-field constants with name-keyed struct fields - #4724
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Codegen single-non-ZST-field constants with name-keyed struct fields#4724tautschnig wants to merge 1 commit into
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try_codegen_constant built the field-value list in declaration order and used the positional struct constructor, but the goto struct type lists fields in LAYOUT order. For constants whose layout reorders fields (e.g. a (Wrap(u8), u16) pair placing the u16 first), this ICEd with 'value type does not match field type' (surfaced by yansi and bitvec in a crates.io autoharness sweep). Key the values by the variant's field names instead. Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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Pull request overview
Fixes an ICE in try_codegen_constant when codegenning struct constants whose field layout order differs from declaration order by switching from positional struct initialization to name-keyed field initialization, aligning with the goto struct’s layout-based field ordering.
Changes:
- Build struct constant initializers as a name-keyed map of field values and use
Expr::struct_exprinstead ofstruct_expr_from_values. - Add a regression test intended to cover layout-vs-declaration field order mismatches in constant struct codegen.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| kani-compiler/src/codegen_cprover_gotoc/codegen/operand.rs | Switch constant struct expansion to name-keyed field initialization to match goto struct layout order. |
| tests/kani/Structs/const_struct_layout_order.rs | Add regression test for struct-constant codegen with layout-reordered fields. |
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| //! Constant structs whose layout order differs from declaration order must codegen with | ||
| //! name-keyed fields (regression: value/field type mismatch ICE in try_codegen_constant). | ||
| //! `Pair` declares (u8-wrapper, u16); layout places the u16 first. | ||
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| #[derive(Clone, Copy, PartialEq)] | ||
| struct Wrap(u8); | ||
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| #[derive(Clone, Copy, PartialEq)] | ||
| struct Pair { | ||
| w: Wrap, | ||
| n: u16, | ||
| } | ||
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| const P: Pair = Pair { w: Wrap(3), n: 512 }; | ||
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| #[kani::proof] | ||
| fn check_const_struct_layout_order() { | ||
| let p = P; | ||
| assert!(p.w == Wrap(3)); | ||
| assert!(p.n == 512); | ||
| } |
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try_codegen_constantbuilt the field-value list in declaration order and used the positional struct constructor, but the goto struct type lists fields in layout order. For constants whose layout reorders fields (e.g. a(Wrap(u8), u16)pair placing theu16first), this ICEd with value type does not match field type.Surfaced by yansi and bitvec in a top-500 crates.io autoharness sweep (tracking #3832); the fix and regression test are independent of autoharness.
Changes
struct_expr) instead of position (struct_expr_from_values).By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.