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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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2
compiler/rustc_span/src/symbol.rs
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@ -1178,7 +1178,6 @@ symbols! {
ptr_cast_const,
ptr_cast_mut,
ptr_const_is_null,
ptr_from_mut,
ptr_from_ref,
ptr_guaranteed_cmp,
ptr_is_null,
@ -1337,6 +1336,7 @@ symbols! {
rustc_main,
rustc_mir,
rustc_must_implement_one_of,
rustc_never_returns_null_ptr,
rustc_nonnull_optimization_guaranteed,
rustc_nounwind,
rustc_object_lifetime_default,