gccrs: add repr_c_enums_larger_than_int lint#4651
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Yeah i think we need to do const eval during type resolution of the enum disriminant variant
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Warn on a `#[repr(C)]` enum whose discriminant fits into neither a C `int` nor a C `unsigned int`. Such an enum is non-portable: C only permits enums whose discriminants do not all fit into one of those two types since C23, and Rust interprets `repr(C)` discriminants as `isize`, so its size may not match the C one. The discriminant is const evaluated with query_compile_const_expr during type resolution, so any constant discriminant expression is handled. gcc/rust/ChangeLog: * typecheck/rust-hir-type-check-item.cc (check_repr_c_enum_discriminants): New. (TypeCheckItem::visit): Check repr(C) enum discriminants. gcc/testsuite/ChangeLog: * rust/compile/repr-c-enums-larger-than-int_0.rs: New test. Signed-off-by: Lucas Ly Ba <lucas.ly-ba@outlook.com>
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Warn on a
#[repr(C)]enum whose discriminant fits into neither a Cintnor a Cunsigned int. Such an enum is non-portable: C only permits enums whose discriminants do not all fit into one of those two types since C23, and Rust interpretsrepr(C)discriminants asisize, so the size may not match the C one.