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Should #[naked] functions default to #[inline(never)] ? #60919

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fintelia opened this issue May 17, 2019 · 2 comments · Fixed by #79192
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Should #[naked] functions default to #[inline(never)] ? #60919

fintelia opened this issue May 17, 2019 · 2 comments · Fixed by #79192
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A-naked Area: `#[naked]`, prologue and epilogue-free, functions, https://git.io/vAzzS C-bug Category: This is a bug. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue.

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@fintelia
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Currently, the compiler is allowed to inline naked functions if it wants to. For a normal function, inlining is fine because the compiler can remove the function prologue/epilogue and the remaining will behave as expected. However for naked functions, the developer provides the prologue/epilogue and those aren't removed by the compiler. This almost surely will result in incorrect behavior. Accordingly I think it would make sense for the compiler to not inline naked functions unless the developer explicitly opted-in.
@fintelia fintelia changed the title Should #[naked] default to #[inline(never)] ? Should #[naked] functions default to #[inline(never)] ? May 17, 2019
@jonas-schievink jonas-schievink added A-naked Area: `#[naked]`, prologue and epilogue-free, functions, https://git.io/vAzzS C-bug Category: This is a bug. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue. labels May 17, 2019
@fintelia fintelia mentioned this issue Sep 27, 2019
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@comex
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comex commented Sep 28, 2019

In the other thread, alistair23 found that Clang automatically marks naked functions as noinline.

@npmccallum
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Yes, #[naked] functions should imply #[inline(never)].

@tmiasko tmiasko mentioned this issue Nov 19, 2020
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Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this issue Nov 19, 2020
@Dylan-DPC
Rollup merge of rust-lang#79192 - tmiasko:naked-noinline, r=oli-obk
b152b83 
Never inline naked functions

The `#[naked]` attribute disabled prologue / epilogue emission for the
function and it is responsibility of a developer to provide them. The
compiler is no position to inline such functions correctly.

Disable inlining of naked functions at LLVM and MIR level.

Closes rust-lang#60919.
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this issue Nov 19, 2020
@Dylan-DPC
Rollup merge of rust-lang#79192 - tmiasko:naked-noinline, r=oli-obk
09b3a8b 
Never inline naked functions

The `#[naked]` attribute disabled prologue / epilogue emission for the
function and it is responsibility of a developer to provide them. The
compiler is no position to inline such functions correctly.

Disable inlining of naked functions at LLVM and MIR level.

Closes rust-lang#60919.
@bors bors closed this as completed in 5c45969 Nov 20, 2020
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A-naked Area: `#[naked]`, prologue and epilogue-free, functions, https://git.io/vAzzS C-bug Category: This is a bug. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-lang Relevant to the language team, which will review and decide on the PR/issue.
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Never inline naked functions tmiasko/rust
4 participants
@comex @npmccallum @jonas-schievink @fintelia