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Support Option and similar enums as type of static variable with linkage attribute #104799

Merged
merged 3 commits into from
Dec 7, 2022
Merged

Support Option and similar enums as type of static variable with linkage attribute #104799

merged 3 commits into from
Dec 7, 2022

Commits on Dec 5, 2022

  1. Move linkage type check to HIR analysis and fix semantics issues. 

    This ensures that the error is printed even for unused variables,
as well as unifying the handling between the LLVM and GCC backends.

This also fixes unusual behavior around exported Rust-defined variables
with linkage attributes. With the previous behavior, it appears to be
impossible to define such a variable such that it can actually be imported
and used by another crate. This is because on the importing side, the
variable is required to be a pointer, but on the exporting side, the
type checker rejects static variables of pointer type because they do
not implement `Sync`. Even if it were possible to import such a type, it
appears that code generation on the importing side would add an unexpected
additional level of pointer indirection, which would break type safety.

This highlighted that the semantics of linkage on Rust-defined variables
is different to linkage on foreign items. As such, we now model the
difference with two different codegen attributes: linkage for Rust-defined
variables, and import_linkage for foreign items.

This change gives semantics to the test
src/test/ui/linkage-attr/auxiliary/def_illtyped_external.rs which was
previously expected to fail to compile. Therefore, convert it into a
test that is expected to successfully compile.

The update to the GCC backend is speculative and untested.
    @pcc
    pcc committed Dec 5, 2022
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  2. Support Option and similar enums as type of static variable with link… 

    …age attribute.

Compiler MCP:
rust-lang/compiler-team#565
    @pcc
    pcc committed Dec 5, 2022
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  3. Reimplement weak! using Option.

    @pcc
    pcc committed Dec 5, 2022
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