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The #[panic_handler] attribute can be applied to non-functions #54896

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phil-opp opened this issue Oct 7, 2018 · 3 comments
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The #[panic_handler] attribute can be applied to non-functions #54896

phil-opp opened this issue Oct 7, 2018 · 3 comments
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@davidtwco
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P-medium Medium priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Rust 2018 Release

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@phil-opp
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phil-opp commented Oct 7, 2018

It's possible to apply the panic_handler attribute to an extern crate statement without errror:

#[panic_handler]
extern crate some_example_crate;

It only causes a linker error:

rust-lld: error: undefined symbol: rust_begin_unwind

(When the panic_handler attribute is not defined there is a much better "#[panic_handler] function required, but not found" error. There is also a nice error when the function signature is wrong. But it seems like the above case is not handled.)
@phil-opp phil-opp mentioned this issue Oct 7, 2018
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@Centril
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Centril commented Oct 7, 2018

cc @japaric

@Centril Centril added P-high High priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 8, 2018
@japaric
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japaric commented Oct 9, 2018

I'm very busy this week and probably won't have time to look at this until next Wednesday but if someone wants to take a stab at this I would look for the logic used by #[global_allocator]: that attribute gives you "error: allocators must be statics" when applied to non-static items.

@pnkfelix
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Visited for triage. Does not seem super critical to resolve immediately. Putting on the Release milestone (rather than RC2) to reflect this, and also downgrading priority to P-medium.

@pnkfelix pnkfelix added this to the Rust 2018 Release milestone Oct 11, 2018
@pnkfelix pnkfelix added P-medium Medium priority and removed P-high High priority labels Oct 11, 2018
@davidtwco davidtwco mentioned this issue Oct 11, 2018
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@davidtwco davidtwco self-assigned this Oct 11, 2018
bors added a commit that referenced this issue Oct 13, 2018
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Auto merge of #54997 - davidtwco:issue-54896, r=nagisa
24faa97 
The #[panic_handler] attribute can be applied to non-functions

Fixes #54896.

This commit extends the existing lang items functionality to assert
that the `#[lang_item]` attribute is only found on the appropriate item
for any given lang item. That is, language items representing traits
must only ever have their corresponding attribute placed on a trait, for
example.

r? @nagisa
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@davidtwco davidtwco

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@pnkfelix @Centril @phil-opp @davidtwco @japaric