refactor: keep the original symbol when renaming an extern declaration - #1945
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refactor: keep the original symbol when renaming an extern declaration
#1945ahomescu wants to merge 2 commits into
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Regression test: `test_reorganize_foreign_static_rename` (`tests/snapshots/reorganize_foreign_static_rename.rs`). Two translation units include the same header, which declares the C global `cfg` directly in one unit and through a `typedef` in the other, so the two declarations are not syntactically identical, cannot be collapsed, and the second is renamed to `cfg_1` to clear the collision. An `extern` static links against its own name unless a `#[link_name]` says otherwise, so the rename quietly repoints the declaration at a symbol named `cfg_1`, which does not exist. Nothing catches this: the output compiles, and only a link of the whole program would fail, so the recorded snapshot is the evidence — it shows `cfg_1` carrying no `#[link_name]`. `test_reorganize_foreign_fn_rename` does the same thing with a function. There the transform compares resolved types, so a `typedef` collapses; the declarations differ instead in a parameter of type `int (*)[]` versus `int (*)[4]`, which C treats as compatible but which transpile to pointers to differently-sized Rust arrays. Both inputs are real `c2rust transpile -r` output, transcribed into the single-file form these tests use, and the C behind them is strictly conforming: an array type of unknown size is compatible with any array type of the same element type (C11 6.7.6.2p6), pointers are compatible when their pointees are, and a `typedef` is an alias rather than a distinct type. So every declaration of `cfg` and of `compute` has compatible type across the program, as C11 6.2.7p2 requires, and the bug does not depend on feeding the transform undefined behavior. Each test records its C sources in a comment.
When two declarations of the same name cannot be collapsed, `move_items` appends a numeric suffix to the second one to clear the collision. For a regular item that is harmless, since it is mangled under its own path, but a foreign function or static links against its own name: renaming one repoints it at a symbol that does not exist, and nothing reports it until the whole program is linked. `MovedDecl::preserve_link_name` now records the original name in a `#[link_name]` before the ident is changed, so the declaration keeps naming the symbol it was written against. It applies only to `ForeignItemKind::Fn` and `Static`, the two kinds that have a symbol — an `extern type` has none — and leaves an existing `#[link_name]` alone, since that already says what to link against and is unaffected by the Rust-side rename. This covers the rename introduced by the previous commit as well: both the `compute_1` function and the `cfg_1` static now carry a `#[link_name]`.
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Fresh copy of #1935 since I closed that one.
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