Remove --fatal-warnings on wasm targets #120278

djkoloski · 2024-01-23T19:21:37Z

These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag.

See this comment on wasm targets' uses of --fatal-warnings.

These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag.

rustbot · 2024-01-23T19:21:45Z

r? @oli-obk

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rustbot · 2024-01-23T19:21:47Z

These commits modify compiler targets.
(See the Target Tier Policy.)

oli-obk · 2024-01-24T08:53:32Z

cc @g0djan @alexcrichton @abrown @loganek

As noted in the linked llvm comment, this will hide all linker warnings on wasm targets, so you may want to look into generally bubbling them up and reporting them in some way

oli-obk · 2024-01-24T08:53:42Z

@bors r+ rollup

bors · 2024-01-24T08:53:45Z

📌 Commit 849d884 has been approved by oli-obk

It is now in the queue for this repository.

…sm, r=oli-obk Remove --fatal-warnings on wasm targets These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag. See [this comment on wasm targets' uses of `--fatal-warnings`](llvm/llvm-project#78658 (comment)).

Rollup of 8 pull requests Successful merges: - rust-lang#119305 (Add `AsyncFn` family of traits) - rust-lang#119389 (Provide more context on recursive `impl` evaluation overflow) - rust-lang#120062 (llvm: change data layout bug to an error and make it trigger more) - rust-lang#120099 (linker: Refactor library linking methods in `trait Linker`) - rust-lang#120201 (Bump some deps with syn 1.0 dependencies) - rust-lang#120230 (Assert that a single scope is passed to `for_scope`) - rust-lang#120278 (Remove --fatal-warnings on wasm targets) - rust-lang#120292 (coverage: Dismantle `Instrumentor` and flatten span refinement) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 10 pull requests Successful merges: - rust-lang#119305 (Add `AsyncFn` family of traits) - rust-lang#119389 (Provide more context on recursive `impl` evaluation overflow) - rust-lang#119895 (Remove `track_errors` entirely) - rust-lang#120230 (Assert that a single scope is passed to `for_scope`) - rust-lang#120278 (Remove --fatal-warnings on wasm targets) - rust-lang#120292 (coverage: Dismantle `Instrumentor` and flatten span refinement) - rust-lang#120315 (On E0308 involving `dyn Trait`, mention trait objects) - rust-lang#120317 (pattern_analysis: Let `ctor_sub_tys` return any Iterator they want) - rust-lang#120318 (pattern_analysis: Reuse most of the `DeconstructedPat` `Debug` impl) - rust-lang#120325 (rustc_data_structures: use either instead of itertools) r? `@ghost` `@rustbot` modify labels: rollup

bjorn3 · 2024-01-25T09:28:09Z

There is a PR to make rustc show all linker warnings. Once that happens the new lld warning would show to all users even though it is not their fault. As such the warning shouls be fixed instead of made non-fatal.

Rollup merge of rust-lang#120278 - djkoloski:remove_fatal_warnings_wasm, r=oli-obk Remove --fatal-warnings on wasm targets These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag. See [this comment on wasm targets' uses of `--fatal-warnings`](llvm/llvm-project#78658 (comment)).

sbc100 · 2024-01-30T20:11:34Z

I the long run it might be better to convert the lib.rmeta files to be valid Wasm object files. This would match the ELF toolchain where lib.rmeta are valid ELF files.

Otherwise any user that sees the stderr of the linker (e.g. in the case of a link failure) will also see all these false-positive warnings on their screen (one per library).

Also, unlike ELF, the Wasm linker produces signature mismatch warnings, which is good to know about and the current setup (IIUC) now hides those because linker stderr is hidden by default.

The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. To avoid bringing in any new dependencies I've opted to hand-code this encoding at this time. If the object gets more complicated though it'd probably be best to pull in `wasmparser` and `wasm-encoder`. For now though there's two adjacent functions reading/writing wasm. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

alexcrichton · 2024-02-02T21:50:46Z

I've attempted to implement the long-run suggestion in #120588 to use wasm object files to store the rustc metadata blob. I'm a bit too scared myself to propose saying rustc should stop swallowing linker output by default.

The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. To avoid bringing in any new dependencies I've opted to hand-code this encoding at this time. If the object gets more complicated though it'd probably be best to pull in `wasmparser` and `wasm-encoder`. For now though there's two adjacent functions reading/writing wasm. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. This enables the `wasm` feature of the `object` crate to be able to read the custom section in the same manner as other platforms, but currently `object` doesn't support writing wasm object files so a handwritten encoder is used instead. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

…wesleywiser wasm: Store rlib metadata in wasm object files The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. To avoid bringing in any new dependencies I've opted to hand-code this encoding at this time. If the object gets more complicated though it'd probably be best to pull in `wasmparser` and `wasm-encoder`. For now though there's two adjacent functions reading/writing wasm. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. This enables the `wasm` feature of the `object` crate to be able to read the custom section in the same manner as other platforms, but currently `object` doesn't support writing wasm object files so a handwritten encoder is used instead. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

…sleywiser,bjorn3 wasm: Store rlib metadata in wasm object files The goal of this commit is to remove warnings using LLVM tip-of-tree `wasm-ld`. In llvm/llvm-project#78658 the `wasm-ld` LLD driver no longer looks at archive indices and instead looks at all the objects in archives. Previously `lib.rmeta` files were simply raw rustc metadata bytes, not wasm objects, meaning that `wasm-ld` would emit a warning indicating so. WebAssembly targets previously passed `--fatal-warnings` to `wasm-ld` by default which meant that if Rust were to update to LLVM 18 then all wasm targets would not work. This immediate blocker was resolved in rust-lang#120278 which removed `--fatal-warnings` which enabled a theoretical update to LLVM 18 for wasm targets. This current state is ok-enough for now because rustc squashes all linker output by default if it doesn't fail. This means, for example, that rustc squashes all the linker warnings coming out of `wasm-ld` about `lib.rmeta` files with LLVM 18. This again isn't a pressing issue because the information is all hidden, but it runs the risk of being annoying if another linker error were to happen and then the output would have all these unrelated warnings that couldn't be fixed. Thus, this PR comes into the picture. The goal of this PR is to resolve these warnings by using the WebAssembly object file format on wasm targets instead of using raw rustc metadata. When I first implemented the rlib-in-objects scheme in rust-lang#84449 I remember either concluding that `wasm-ld` would either include the metadata in the output or I thought we didn't have to do anything there at all. I think I was wrong on both counts as `wasm-ld` does not include the metadata in the final output unless the object is referenced and we do actually need to do something to resolve these warnings. This PR updates the object file format containing rustc metadata on WebAssembly targets to be an actual WebAssembly file. To avoid bringing in any new dependencies I've opted to hand-code this encoding at this time. If the object gets more complicated though it'd probably be best to pull in `wasmparser` and `wasm-encoder`. For now though there's two adjacent functions reading/writing wasm. The only caveat I know of with this is that if `wasm-ld` does indeed look at the object file then the metadata will be included in the final output. I believe the only thing that could cause that at this time is `--whole-archive` which I don't think is passed for rlibs. I would clarify that I'm not 100% certain about this, however.

rustbot assigned oli-obk Jan 23, 2024

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 24, 2024

fmease mentioned this pull request Jan 24, 2024

Rollup of 8 pull requests #120304

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matthiaskrgr mentioned this pull request Jan 25, 2024

Rollup of 10 pull requests #120335

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bors merged commit 565961b into rust-lang:master Jan 25, 2024
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rustbot added this to the 1.77.0 milestone Jan 25, 2024

alexcrichton mentioned this pull request Jan 30, 2024

[lld][WebAssembly] Match the ELF linker in transitioning away from archive indexes. llvm/llvm-project#78658

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alexcrichton mentioned this pull request Feb 2, 2024

wasm: Store rlib metadata in wasm object files #120588

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workingjubilee added the O-wasm Target: WASM (WebAssembly), http://webassembly.org/ label May 4, 2024

tgross35 mentioned this pull request Aug 12, 2024

[experiment] Make all linker warnings errors rust-lang/compiler-builtins#667

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Remove --fatal-warnings on wasm targets #120278

Remove --fatal-warnings on wasm targets #120278

djkoloski commented Jan 23, 2024

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alexcrichton commented Feb 2, 2024

Remove --fatal-warnings on wasm targets #120278

Remove --fatal-warnings on wasm targets #120278

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