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› Proc-macro2 › Reviews

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The current version of Proc-macro2 is 1.0.81.

1.0.74 — diff review from 1.0.71 only (older version) safe-to-deploy

From zcash/rust-ecosystem copy of zcash/zcash. By str4d.

Build script changes are to replace RUSTFLAGS string parsing with a probe file that is compiled with whatever RUSTC is set to (but the build script already relies on the RUSTC environment variable for inspecting the compiler version).

1.0.39 (older version) safe-to-deploy

From mozilla/supply-chain copy of hg. By Nika Layzell.

proc-macro2 acts as either a thin(-ish) wrapper around the std-provided proc_macro crate, or as a fallback implementation of the crate, depending on where it is used.

If using this crate on older versions of rustc (1.56 and earlier), it will temporarily replace the panic handler while initializing in order to detect if it is running within a proc_macro, which could lead to surprising behaviour. This should not be an issue for more recent compiler versions, which support proc_macro::is_available().

The proc-macro2 crate's fallback behaviour is not identical to the complex behaviour of the rustc compiler (e.g. it does not perform unicode normalization for identifiers), however it behaves well enough for its intended use-case (tests and scripts processing rust code).

proc-macro2 does not use unsafe code, however exposes one unsafe API to allow bypassing checks in the fallback implementation when constructing Literal using from_str_unchecked. This was intended to only be used by the quote! macro, however it has been removed (https://github.com/dtolnay/quote/commit/f621fe64a8a501cae8e95ebd6848e637bbc79078), and is likely completely unused. Even when used, this API shouldn't be able to cause unsoundness.

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safe-to-deploy (implies safe-to-run)

This crate will not introduce a serious security vulnerability to production software exposed to untrusted input. More…

safe-to-run

This crate can be compiled, run, and tested on a local workstation or in controlled automation without surprising consequences. More…

does-not-implement-crypto (implies crypto-safe)

Inspection reveals that the crate in question does not attempt to implement any cryptographic algorithms on its own.

Note that certification of this does not require an expert on all forms of cryptography: it's expected for crates we import to be "good enough" citizens, so they'll at least be forthcoming if they try to implement something cryptographic. When in doubt, please ask an expert.

crypto-safe
Implied by other criteria

All crypto algorithms in this crate have been reviewed by a relevant expert.

Note: If a crate does not implement crypto, use does-not-implement-crypto, which implies crypto-safe, but does not require expert review in order to audit for.

ub-risk-2 (implies ub-risk-3)

Negligible unsoundness or average soundness.

Full description of the audit criteria can be found at https://github.com/google/rust-crate-audits/blob/main/auditing_standards.md#ub-risk-2

ub-risk-3 (implies ub-risk-4)
Implied by other criteria

Mild unsoundness or suboptimal soundness.

Full description of the audit criteria can be found at https://github.com/google/rust-crate-audits/blob/main/auditing_standards.md#ub-risk-3

ub-risk-4
Implied by other criteria

Extreme unsoundness.

Full description of the audit criteria can be found at https://github.com/google/rust-crate-audits/blob/main/auditing_standards.md#ub-risk-4

unknown

May have been packaged automatically without a review

Lib.rs has been able to verify that all files in the crate's tarball are in the crate's repository with a git tag matching the version. Please note that this check is still in beta, and absence of this confirmation does not mean that the files don't match.

Crates in the crates.io registry are tarball snapshots uploaded by crates' publishers. The registry is not using crates' git repositories, so there is a possibility that published crates have a misleading repository URL, or contain different code from the code in the repository.

To review the actual code of the crate, it's best to use cargo crev open proc-macro2. Alternatively, you can download the tarball of proc-macro2 v1.0.81 or view the source online.