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rustc could provide more help for debugging no_std duplicate_lang item errors #60561

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brenzi opened this issue May 5, 2019 · 1 comment · Fixed by #64883
Closed

rustc could provide more help for debugging no_std duplicate_lang item errors #60561

brenzi opened this issue May 5, 2019 · 1 comment · Fixed by #64883
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A-diagnostics Area: Messages for errors, warnings, and lints A-lang-item Area: lang items C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@brenzi
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brenzi commented May 5, 2019

I'm currently porting crates to support no_std to use them with https://github.com/baidu/rust-sgx-sdk

The Problem:
any sub-dependency can break no_std, resulting in an error like this:

error: duplicate lang item in crate `std`: `f32_runtime`.
  |
  = note: first defined in crate `sgx_tstd`.

error: duplicate lang item in crate `std`: `f64_runtime`.
  |
  = note: first defined in crate `sgx_tstd`.

error: duplicate lang item in crate `std`: `panic_impl`.
  |
  = note: first defined in crate `sgx_tstd`.

error: duplicate lang item in crate `std`: `oom`.
  |
  = note: first defined in crate `sgx_trts`.

The compiler doesn't give me any hint, which (sub)dependency causes this issue. Like this it is very annoying and time-consuming to sort out such errors.

Would it be possible that rustc gives us a hint to colliding crates?

Maybe something like https://github.com/sfackler/cargo-tree could help visualizing no_std crates automatically?
@jonas-schievink jonas-schievink added A-diagnostics Area: Messages for errors, warnings, and lints C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels May 5, 2019
@varkor varkor added the A-lang-item Area: lang items label May 8, 2019
@BaoshanPang
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I am seeing this problem too, it is really painful to figure out what's the problem.

@brenzi brenzi mentioned this issue May 11, 2019
Open
@tomtau tomtau mentioned this issue Sep 22, 2019
Merged
Centril added a commit to Centril/rust that referenced this issue Sep 28, 2019
@Centril
Rollup merge of rust-lang#64678 - tomtau:fix/no-std-error, r=matthewj…
05881d0 
…asper

added more context for duplicate lang item errors (fixes rust-lang#60561)

Some more information about rust-lang#60561 -- these errors are pretty common when one works in restrictive environments with `no_std` or customized `std`, but they don't provide much context for debugging, as any transitive dependency could have brought in `std` crate. With that, currently, one needs to use something like `cargo tree` and investigate transitive dependencies one by one.

It'll be more helpful to know at least the crate that uses `std` (which `cargo tree` doesn't show) to pin down this investigation when debugging.

I'm not sure what the best way to get this context is inside rustc internals (I'm new to them). I found that `all_crate_nums` query returns the crates in some dependency order, so printing out the name of the preceding crate seems to do the trick. But I welcome suggestions if this can be done in a better way.
@Centril Centril mentioned this issue Sep 28, 2019
Merged
bors added a commit that referenced this issue Sep 28, 2019
@bors
Auto merge of #64883 - Centril:rollup-uehjt63, r=Centril
b61e694 
Rollup of 10 pull requests

Successful merges:

 - #64131 (data_structures: Add deterministic FxHashMap and FxHashSet wrappers)
 - #64387 (Fix redundant semicolon lint interaction with proc macro attributes)
 - #64678 (added more context for duplicate lang item errors (fixes #60561))
 - #64763 (Add E0734 and its long explanation)
 - #64793 (Fix format macro expansions spans to be macro-generated)
 - #64837 (Improve wording in documentation of MaybeUninit)
 - #64852 (Print ParamTy span when accessing a field (#52082))
 - #64875 (Upgrade async/await to "used" keywords.)
 - #64876 (Fix typo in intrinsics op safety)
 - #64880 (Slice docs: fix typo)

Failed merges:

r? @ghost
@bors bors closed this as completed in ac9aed5 Sep 29, 2019
@brenzi brenzi mentioned this issue Sep 30, 2019
Open
andjo403 pushed a commit to andjo403/rust that referenced this issue Oct 4, 2019
@tomtau @andjo403
getting more context for duplicate lang items (fixes rust-lang#60561)
0fe8a8f 
Where possible, the error message includes the name of the crate
that brought in the crate with duplicate lang items (which
helps with debugging). This information is passed on from cstore
using the `extern_crate` query.
@dingelish dingelish mentioned this issue Oct 9, 2019
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A-diagnostics Area: Messages for errors, warnings, and lints A-lang-item Area: lang items C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Rollup of 10 pull requests Centril/rust
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@jonas-schievink @BaoshanPang @varkor @brenzi