Add regression test for CString::clone_into unwind safety#158807
Open
Vastargazing wants to merge 1 commit into
Open
Add regression test for CString::clone_into unwind safety#158807Vastargazing wants to merge 1 commit into
Vastargazing wants to merge 1 commit into
Conversation
CString::clone_into reuses the target's allocation by moving the buffer into a Vec and growing it. If that growth's allocation fails and the alloc error hook unwinds, the target has to be left as a valid CString, but nothing covered that path. Add a test in library/alloctests that fails the reallocation under a panicking alloc error hook and checks the target stays valid. The failing allocator is only honored under Miri - a global allocator in a library test doesn't intercept libstd's allocation in a normal build - so the unwind assertion is gated on cfg!(miri); the test still runs and passes as a regular test.
rustbot
added
S-waiting-on-review
Collaborator
|
|
Member
|
LGTM, thanks :) @bors r+ rollup |
Contributor
rust-bors
Bot
added
S-waiting-on-bors
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Jul 5, 2026
…-alloc-error, r=RalfJung Add regression test for CString::clone_into unwind safety Regression test for the panic-safety fix in rust-lang#155707 rust-lang#70201 gave `<CStr as ToOwned>::clone_into` a path that moved the target `CString`'s buffer out (leaving it empty) before growing a `Vec`; if that growth's allocation failed and unwound, the target was left without its nul terminator, which is UB. rust-lang#155707 fixed this but didn't add a test. The failing allocator here is only honored under Miri - in a normal build a `#[global_allocator]` in a library test doesn't intercept the reallocation inside `CString::clone_into` (it lives in libstd, linked `-C prefer-dynamic`). So the test passes as a regular test and does the real check under Miri, with the unwind assertion gated on `cfg!(miri)`; it runs under Miri in CI via the library-tests-under-Miri job. This started as rust-lang/miri#5157, but per @RalfJung a std regression test belongs with the standard library. r? @RalfJung
jhpratt
added a commit
to jhpratt/rust
that referenced
this pull request
Jul 6, 2026
…-alloc-error, r=RalfJung Add regression test for CString::clone_into unwind safety Regression test for the panic-safety fix in rust-lang#155707 rust-lang#70201 gave `<CStr as ToOwned>::clone_into` a path that moved the target `CString`'s buffer out (leaving it empty) before growing a `Vec`; if that growth's allocation failed and unwound, the target was left without its nul terminator, which is UB. rust-lang#155707 fixed this but didn't add a test. The failing allocator here is only honored under Miri - in a normal build a `#[global_allocator]` in a library test doesn't intercept the reallocation inside `CString::clone_into` (it lives in libstd, linked `-C prefer-dynamic`). So the test passes as a regular test and does the real check under Miri, with the unwind assertion gated on `cfg!(miri)`; it runs under Miri in CI via the library-tests-under-Miri job. This started as rust-lang/miri#5157, but per @RalfJung a std regression test belongs with the standard library. r? @RalfJung
rust-bors Bot
pushed a commit
that referenced
this pull request
Jul 6, 2026
Rollup of 20 pull requests Successful merges: - #158377 (add `-Zforce-intrinsic-fallback` flag) - #158642 (Clarify some interning details) - #158743 (Look for cdb location in the registry first) - #158775 (bootstrap: only encode RUSTFLAGS when a flag contains a space) - #158782 (Add and use cfg(target_has_threads) to enforce no_thread impl usage) - #158785 (hook intrinsic-test into aarch64-gnu) - #157734 (Stabilize `local_key_cell_update`) - #158183 (std: allocate less memory in `current_exe` for OpenBSD) - #158671 (Move tests batch 17) - #158730 (Update `FIXME(static_mut_refs)` comments) - #158752 (Reorganize `tests/ui/issues` [18/N]) - #158755 (Use `ThinVec` more in the AST) - #158757 (Fix incorrect tracking issue for `read_le`/`read_be`) - #158765 (Fix ICE on non-ident path in `doc(auto_cfg values)`) - #158771 (library: expand HashSet::extract_if coverage) - #158772 (rustc-dev-guide subtree update) - #158776 (fix: emit diagnostic for AVR target without target-cpu) - #158786 (Add regression test for builtin attr macro values) - #158807 (Add regression test for CString::clone_into unwind safety) - #158825 (Fix typo)
Member
|
Look like you've got some UB in the test. |
rust-bors
Bot
added
S-waiting-on-author
Contributor
|
This pull request was unapproved. |
Contributor
Author
|
Thanks. The UB is in libtest's own teardown, not the test body: with a #[global_allocator] installed, libtest frees its internal allocations (the mpmc results channel) through it, and on Windows System::dealloc reads the allocation header just before the pointer, which trips Stacked Borrows since the freed Box's provenance doesn't cover the header. It fires even with 0 tests run - it's inherent to wrapping System in a global allocator under Miri on Windows, independent of the test itself. Two ways to resolve it, whichever you'd prefer:
Happy to do either - which do you prefer? |
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
4 participants
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.
Regression test for the panic-safety fix in #155707
#70201 gave
<CStr as ToOwned>::clone_intoa path that moved the targetCString's buffer out (leaving it empty) before growing aVec; if that growth's allocation failed and unwound, the target was left without its nul terminator, which is UB. #155707 fixed this but didn't add a test.The failing allocator here is only honored under Miri - in a normal build a
#[global_allocator]in a library test doesn't intercept the reallocation insideCString::clone_into(it lives in libstd, linked-C prefer-dynamic). So the test passes as a regular test and does the real check under Miri, with the unwind assertion gated oncfg!(miri); it runs under Miri in CI via the library-tests-under-Miri job.This started as rust-lang/miri#5157, but per @RalfJung a std regression test belongs with the standard library.
r? @RalfJung