Make useless_ptr_null_checks smarter about some std functions #114494
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And look for it in the useless_ptr_null_checks lint
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Good point about the function that returns a reference, I suppose I've missed that. Also good point about the doc vs implementation discrepancy. I've removed the addition of the attribute from this PR and opened #114517 for discussion what to do about the discrepancy. It can then be resolved in a new PR. |
Add the attribute to standard library functions that are guaranteed to never return null pointers, as their originating data wouldn't allow it.
It was added by rust-lang#113657 for its purposes. Now it is not used any more, remove it, as we use the attr now.
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Sorry about the delay here. I think the std side is fine, but I can't review the compiler changes. r? compiler |
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@bors r+ |
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☀️ Test successful - checks-actions |
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Finished benchmarking commit (635c4a5): comparison URL. Overall result: no relevant changes - no action needed@rustbot label: -perf-regression Instruction countThis benchmark run did not return any relevant results for this metric. Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 632.106s -> 632.885s (0.12%) |
This teaches the
useless_ptr_null_checkslint 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 bootstrapcfg_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