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Auto merge of #114494 - est31:extend_useless_ptr_null_checks, r=jackh726

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Make useless_ptr_null_checks smarter about some std functions

This teaches the `useless_ptr_null_checks` lint that some std functions can't ever return null pointers, because they need to point to valid data, get references as input, etc.

This is achieved by introducing an `#[rustc_never_returns_null_ptr]` attribute and adding it to these std functions (gated behind bootstrap `cfg_attr`).

Later on, the attribute could maybe be used to tell LLVM that the returned pointer is never null. I don't expect much impact of that though, as the functions are pretty shallow and usually the input data is already never null.

Follow-up of PR #113657

Fixes #114442
This commit is contained in:
bors 2023-09-16 03:40:20 +00:00
commit 635c4a5e61
18 changed files with 94 additions and 46 deletions
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4
compiler/rustc_feature/src/builtin_attrs.rs
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@ -699,6 +699,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
"#[rustc_pass_by_value] is used to mark types that must be passed by value instead of reference."
),
rustc_attr!(
rustc_never_returns_null_ptr, Normal, template!(Word), ErrorFollowing,
"#[rustc_never_returns_null_ptr] is used to mark functions returning non-null pointers."
),
rustc_attr!(
rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, @only_local: true,
"#![rustc_coherence_is_core] allows inherent methods on builtin types, only intended to be used in `core`."