refactor: keep the original symbol when renaming an extern declaration #1945
Open
ahomescu wants to merge 2 commits into
Open
refactor: keep the original symbol when renaming an extern declaration
#1945ahomescu wants to merge 2 commits into
ahomescu wants to merge 2 commits into
Conversation
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/preserve_extern_link_name
branch
from
July 25, 2026 03:13
be5a534 to
3ba5ded
Compare
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/non_ascii_idents
branch
from
July 25, 2026 03:17
81bf2f0 to
a2771af
Compare
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/preserve_extern_link_name
branch
from
July 25, 2026 03:17
3ba5ded to
c4d9955
Compare
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/non_ascii_idents
branch
from
July 25, 2026 03:26
a2771af to
476788d
Compare
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/preserve_extern_link_name
branch
from
July 25, 2026 03:26
c4d9955 to
0f16dcf
Compare
ahomescu
changed the base branch from
ahomescu/fix_reorganize_definitions/non_ascii_idents
to
master
July 25, 2026 05:09
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/preserve_extern_link_name
branch
from
July 25, 2026 05:09
0f16dcf to
372a77b
Compare
ahomescu
marked this pull request as ready for review
July 25, 2026 05:09
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]`.
ahomescu
force-pushed
the
ahomescu/fix_reorganize_definitions/preserve_extern_link_name
branch
from
July 25, 2026 05:33
372a77b to
10fb614
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Fresh copy of #1935 since I closed that one.
Stack created with GitHub Stacks CLI • Give Feedback 💬