rust-lang/rust-clippy

Lint to warn about str::as_ptr() usage in ffi call

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#1,236 opened on Sep 19, 2016

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A-lintL-correctnessT-middlegood first issue

Description

Hello. It would be nice to have a warning when using str::as_ptr() in a ffi call instead of using CStr.

For instance, in the following code:

unsafe { printf("Hello".as_ptr() as *const _) };

should give a warning and propose something like:

let cstring = CString::new("Hello".as_bytes()).unwrap();
unsafe { printf(cstring.as_ptr()) };

Thanks to add this lint.

Contributor guide

Tech stack
rust
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
familiarity with Rust FFIclippy lint creation basicsunderstanding of CStr
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Examine existing clippy lints that target function calls (e.g., the 'fn to numeric cast' lint) to understand the pattern matching on function arguments. Follow the clippy development guide at https://github.com/rust lang/rust clippy/blob/master/CONTRIBUTING.md to set up the environment and add a new lint. The lint should detect calls to `str::as ptr()` where the result is passed to an extern function; consider using `fn has item` or checking the function call's parameter types.
Lint to warn about str::as_ptr() usage in ffi call · rust-lang/rust-clippy#1236 | Good First Issue