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Remove src/tools/rust-demangler #754

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Zalathar opened this issue Jun 2, 2024 · 3 comments
Closed
1 of 3 tasks

Remove src/tools/rust-demangler #754

Zalathar opened this issue Jun 2, 2024 · 3 comments
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major-change A proposal to make a major change to rustc major-change-accepted A major change proposal that was accepted T-compiler Add this label so rfcbot knows to poll the compiler team to-announce Announce this issue on triage meeting

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@Zalathar
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Zalathar commented Jun 2, 2024

Proposal


rust-demangler is a small binary that reads a list of mangled symbols from stdin, demangles them (using the rustc-demangle library crate), and prints the demangled symbols to stdout.

It was added as part of the initial implementation of coverage instrumentation in 2020/2021, so that coverage tests could pass it to llvm-cov --Xdemangler when generating coverage reports. It has been largely untouched since then.

As of rust-lang/rust#125816 it is no longer used by coverage tests, and has no remaining in-tree uses.

There is code in bootstrap to build and package the demangler, but it's unclear where the resulting binaries actually end up, or whether there's any reasonable way for rustup users to obtain them.


For users needing a command-line demangler, rustfilt exists and is more actively maintained. It's also quite easy to use the rustc-demangle library to build a custom command-line demangler if necessary, with only a few lines of code.

The tool's name (rust-demangler) is easily confused with the name of the library crate rustc-demangle, so removing the tool will eliminate that confusion. There also doesn't appear to be much reason to use rust-demangler over rustfilt.

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Process

The main points of the Major Change Process are as follows:

  • File an issue describing the proposal.
  • A compiler team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
    • Finding a "second" suffices for internal changes. If however, you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
    • Compiler team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
  • Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

Comments

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

@Zalathar Zalathar added major-change A proposal to make a major change to rustc T-compiler Add this label so rfcbot knows to poll the compiler team labels Jun 2, 2024
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rustbot commented Jun 2, 2024

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

Concerns or objections to the proposal should be discussed on Zulip and formally registered here by adding a comment with the following syntax:

@rustbot concern reason-for-concern 
<description of the concern> 

Concerns can be lifted with:

@rustbot resolve reason-for-concern 

See documentation at https://forge.rust-lang.org

cc @rust-lang/compiler @rust-lang/compiler-contributors

@rustbot rustbot added the to-announce Announce this issue on triage meeting label Jun 2, 2024
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@rustbot second

@rustbot rustbot added the final-comment-period The FCP has started, most (if not all) team members are in agreement label Jun 2, 2024
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Jun 7, 2024
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@rustbot label -final-comment-period +major-change-accepted

@rustbot rustbot added major-change-accepted A major change proposal that was accepted to-announce Announce this issue on triage meeting and removed final-comment-period The FCP has started, most (if not all) team members are in agreement labels Jun 19, 2024
fmease added a commit to fmease/rust that referenced this issue Jun 19, 2024
Remove `src/tools/rust-demangler`

`rust-demangler` is a small binary that reads a list of mangled symbols from stdin, demangles them (using the `rustc-demangle` library crate), and prints the demangled symbols to stdout.

It was added as part of the initial implementation of coverage instrumentation in 2020/2021, so that coverage tests could pass it to `llvm-cov --Xdemangler` when generating coverage reports. It has been largely untouched since then.

As of rust-lang#125816 it is no longer used by coverage tests, and has no remaining in-tree uses.

There is code in bootstrap to build and package the demangler, but it's unclear where the resulting binaries actually end up, or whether there's any reasonable way for `rustup` users to obtain them.

---

For users needing a command-line demangler, `rustfilt` exists and is more actively maintained. It's also quite easy to use the `rustc-demangle` library to build a custom command-line demangler if necessary, with only a few lines of code.

The tool's name (`rust-demangler`) is easily confused with the name of the library crate `rustc-demangle`, so removing the tool will eliminate that confusion. There also doesn't appear to be much reason to use `rust-demangler` over `rustfilt`.

---

This PR therefore removes the tool, and removes all of its associated code from bootstrap.

MCP filed: rust-lang/compiler-team#754
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Jun 19, 2024
Rollup merge of rust-lang#125880 - Zalathar:demangler, r=oli-obk

Remove `src/tools/rust-demangler`

`rust-demangler` is a small binary that reads a list of mangled symbols from stdin, demangles them (using the `rustc-demangle` library crate), and prints the demangled symbols to stdout.

It was added as part of the initial implementation of coverage instrumentation in 2020/2021, so that coverage tests could pass it to `llvm-cov --Xdemangler` when generating coverage reports. It has been largely untouched since then.

As of rust-lang#125816 it is no longer used by coverage tests, and has no remaining in-tree uses.

There is code in bootstrap to build and package the demangler, but it's unclear where the resulting binaries actually end up, or whether there's any reasonable way for `rustup` users to obtain them.

---

For users needing a command-line demangler, `rustfilt` exists and is more actively maintained. It's also quite easy to use the `rustc-demangle` library to build a custom command-line demangler if necessary, with only a few lines of code.

The tool's name (`rust-demangler`) is easily confused with the name of the library crate `rustc-demangle`, so removing the tool will eliminate that confusion. There also doesn't appear to be much reason to use `rust-demangler` over `rustfilt`.

---

This PR therefore removes the tool, and removes all of its associated code from bootstrap.

MCP filed: rust-lang/compiler-team#754
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