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dtolnay opened this issue Sep 19, 2017 · 4 comments · Fixed by #62476
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Hangs on derive macro invoked by format string macro #44692

dtolnay opened this issue Sep 19, 2017 · 4 comments · Fixed by #62476
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@pnkfelix @petrochenkov
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A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) C-bug Category: This is a bug. I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. P-high High priority regression-from-stable-to-stable Performance or correctness regression from one stable version to another. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@dtolnay
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dtolnay commented Sep 19, 2017

The compiler hangs when compiling the following code.

macro_rules! hang {
    () => {
        {
            #[derive(Clone)]
            struct S;

            ""
        }
    }
}

fn main() {
    format_args!(hang!());
}

This is a regression in 1.20.0. The same code terminates with an error "format argument must be a string literal" in 1.19.0, which is the correct behavior.
@aidanhs aidanhs added the C-bug Category: This is a bug. label Sep 19, 2017
@steffengy steffengy mentioned this issue Jan 11, 2018
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@dtolnay dtolnay added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. regression-from-stable-to-stable Performance or correctness regression from one stable version to another. A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) I-compiletime Issue: Problems and improvements with respect to compile times. labels Feb 19, 2019
@dtolnay
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dtolnay commented Feb 19, 2019

According to @steffengy in #47188 (comment) -- this is hitting an infinite loop in libsyntax_pos/lib.rs#macro_backtrace. See that comment for details.

@dtolnay dtolnay mentioned this issue Feb 19, 2019
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@dtolnay dtolnay added I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. and removed I-compiletime Issue: Problems and improvements with respect to compile times. labels Jul 3, 2019
This was referenced Jul 3, 2019
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@dtolnay
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dtolnay commented Jul 3, 2019

Transferring nomination by @jonas-schievink in #62167.

@pnkfelix
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pnkfelix commented Jul 4, 2019

triage: P-high. Removing nomination. Assigning to @petrochenkov for primary investigation, and to myself to follow up on it.

@pnkfelix pnkfelix added P-high High priority and removed I-nominated labels Jul 4, 2019
@petrochenkov
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Accidentally fixed in #62476.

@petrochenkov petrochenkov mentioned this issue Jul 8, 2019
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petrochenkov added a commit to petrochenkov/rust that referenced this issue Jul 10, 2019
@petrochenkov
Add a regression test for rust-lang#44692
e86e5cb 
Add a test for the issue resolved by removing `resolve_macro_path`

Add a test making sure that extern prelude entries introduced from an opaque macro are not visible anywhere, even it that macro

Fix test output after rebase
Centril added a commit to Centril/rust that referenced this issue Jul 11, 2019
@Centril
Rollup merge of rust-lang#62476 - petrochenkov:expref, r=matthewjasper
7697b29 
Continue refactoring macro expansion and resolution

This PR continues the work started in rust-lang#62042.
It contains a set of more or less related refactorings with the general goal of making things simpler and more orthogonal.
Along the way most of the issues uncovered in rust-lang#62086 are fixed.

The PR is better read in per-commit fashion with whitespace changes ignored.
I tried to leave some more detailed commit messages describing the motivation behind the individual changes.

Fixes rust-lang#44692
Fixes rust-lang#52363
Unblocks rust-lang#62086
r? @matthewjasper
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Labels
A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) C-bug Category: This is a bug. I-hang Issue: The compiler never terminates, due to infinite loops, deadlock, livelock, etc. P-high High priority regression-from-stable-to-stable Performance or correctness regression from one stable version to another. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Continue refactoring macro expansion and resolution petrochenkov/rust
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@pnkfelix @aidanhs @dtolnay @petrochenkov