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Auto merge of #7243 - mgacek8:issue7145_strlen_on_c_strings, r=giraffate
Add new lint: `strlen_on_c_strings` ~~This is WIP, linting in case of `CString` has been added, but for `CStr`, its diagnostic item needs to be available for clippy. [PR that adds diagnostic item for CStr on rust repo](rust-lang/rust#85439 Ready for the review. Please take a look. fixes #7145 changelog: Add new lint: `strlen_on_c_strings`, that lints on `libc::strlen(some_cstring.as_ptr())`
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,82 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_sugg; | ||
| use clippy_utils::in_macro; | ||
| use clippy_utils::paths; | ||
| use clippy_utils::source::snippet_with_macro_callsite; | ||
| use clippy_utils::ty::{is_type_diagnostic_item, is_type_ref_to_diagnostic_item}; | ||
| use if_chain::if_chain; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir as hir; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_span::symbol::{sym, Symbol}; | ||
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| declare_clippy_lint! { | ||
| /// **What it does:** Checks for usage of `libc::strlen` on a `CString` or `CStr` value, | ||
| /// and suggest calling `as_bytes().len()` or `to_bytes().len()` respectively instead. | ||
| /// | ||
| /// **Why is this bad?** This avoids calling an unsafe `libc` function. | ||
| /// Currently, it also avoids calculating the length. | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// | ||
| /// ```rust, ignore | ||
| /// use std::ffi::CString; | ||
| /// let cstring = CString::new("foo").expect("CString::new failed"); | ||
| /// let len = unsafe { libc::strlen(cstring.as_ptr()) }; | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust, no_run | ||
| /// use std::ffi::CString; | ||
| /// let cstring = CString::new("foo").expect("CString::new failed"); | ||
| /// let len = cstring.as_bytes().len(); | ||
| /// ``` | ||
| pub STRLEN_ON_C_STRINGS, | ||
| complexity, | ||
| "using `libc::strlen` on a `CString` or `CStr` value, while `as_bytes().len()` or `to_bytes().len()` respectively can be used instead" | ||
| } | ||
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| declare_lint_pass!(StrlenOnCStrings => [STRLEN_ON_C_STRINGS]); | ||
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| impl LateLintPass<'tcx> for StrlenOnCStrings { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { | ||
| if in_macro(expr.span) { | ||
| return; | ||
| } | ||
|
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||
| if_chain! { | ||
| if let hir::ExprKind::Call(func, [recv]) = expr.kind; | ||
| if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = func.kind; | ||
|
|
||
| if (&paths::LIBC_STRLEN).iter().map(|x| Symbol::intern(x)).eq( | ||
| path.segments.iter().map(|seg| seg.ident.name)); | ||
| if let hir::ExprKind::MethodCall(path, _, args, _) = recv.kind; | ||
| if args.len() == 1; | ||
| if !args.iter().any(|e| e.span.from_expansion()); | ||
| if path.ident.name == sym::as_ptr; | ||
| then { | ||
| let cstring = &args[0]; | ||
| let ty = cx.typeck_results().expr_ty(cstring); | ||
| let val_name = snippet_with_macro_callsite(cx, cstring.span, ".."); | ||
| let sugg = if is_type_diagnostic_item(cx, ty, sym::cstring_type){ | ||
| format!("{}.as_bytes().len()", val_name) | ||
| } else if is_type_ref_to_diagnostic_item(cx, ty, sym::CStr){ | ||
| format!("{}.to_bytes().len()", val_name) | ||
| } else { | ||
| return; | ||
| }; | ||
|
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||
| span_lint_and_sugg( | ||
| cx, | ||
| STRLEN_ON_C_STRINGS, | ||
| expr.span, | ||
| "using `libc::strlen` on a `CString` or `CStr` value", | ||
| "try this (you might also need to get rid of `unsafe` block in some cases):", | ||
| sugg, | ||
| Applicability::Unspecified // Sometimes unnecessary `unsafe` block | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,16 @@ | ||
| #![warn(clippy::strlen_on_c_strings)] | ||
| #![allow(dead_code)] | ||
| #![feature(rustc_private)] | ||
| extern crate libc; | ||
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| use std::ffi::{CStr, CString}; | ||
|
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| fn main() { | ||
| // CString | ||
| let cstring = CString::new("foo").expect("CString::new failed"); | ||
| let len = unsafe { libc::strlen(cstring.as_ptr()) }; | ||
|
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||
| // CStr | ||
| let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed"); | ||
| let len = unsafe { libc::strlen(cstr.as_ptr()) }; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,25 @@ | ||
| error: using `libc::strlen` on a `CString` or `CStr` value | ||
| --> $DIR/strlen_on_c_strings.rs:11:24 | ||
| | | ||
| LL | let len = unsafe { libc::strlen(cstring.as_ptr()) }; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: `-D clippy::strlen-on-c-strings` implied by `-D warnings` | ||
| help: try this (you might also need to get rid of `unsafe` block in some cases): | ||
| | | ||
| LL | let len = unsafe { cstring.as_bytes().len() }; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^ | ||
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| error: using `libc::strlen` on a `CString` or `CStr` value | ||
| --> $DIR/strlen_on_c_strings.rs:15:24 | ||
| | | ||
| LL | let len = unsafe { libc::strlen(cstr.as_ptr()) }; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| help: try this (you might also need to get rid of `unsafe` block in some cases): | ||
| | | ||
| LL | let len = unsafe { cstr.to_bytes().len() }; | ||
| | ^^^^^^^^^^^^^^^^^^^^^ | ||
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| error: aborting due to 2 previous errors | ||
|
|