Support v0 mangling better

[jrmuizel]

Using the new mangling scheme is convenient because it gives more information about the particular monomorphization. However it seems like crate detection is broken.

RUSTFLAGS="-Z symbol-mangling-version=v0" rustup run nightly cargo bloat --release
gives

0.0%   0.7% 61.2KiB    [Unknown] <gleam[d1379dfb6ebdd7c7]::ffi_gl::Gl>::load_with::<wrench[a4e3b033c434546e]::make_window::{closure#0}
0.0%   0.7% 61.1KiB    [Unknown] <gleam[d1379dfb6ebdd7c7]::ffi_gl::Gl>::load_with::<wrench[a4e3b033c434546e]::make_window
0.0%   0.6% 52.5KiB    [Unknown] <wrench[a4e3b033c434546e]::yaml_frame_writer::YamlFrameWriter>
0.0%   0.6% 47.6KiB regex_syntax <regex_syntax[f84e6df1bfbac060]::ast::parse::ParserI<&mut regex_syntax[f84e6df1bfbac060]::ast::parse::Parser>>
0.0%   0.5% 40.2KiB    [Unknown] <webrender[58737326ba1c09f4]::display_list_flattener::DisplayListFlattener>
0.0%   0.5% 37.5KiB    [Unknown] <wrench[a4e3b033c434546e]::rawtest::RawtestHarness>
0.0%   0.5% 37.3KiB    [Unknown] <wrench[a4e3b033c434546e]::yaml_frame_reader::YamlFrameReader>
0.0%   0.4% 35.1KiB    [Unknown] wrench[a4e3b033c434546e]
0.0%   0.4% 34.7KiB    [Unknown] <webrender[58737326ba1c09f4]::render_backend::RenderBackend>
0.0%   0.4% 33.7KiB    webrender <webrender[58737326ba1c09f4]::renderer::Renderer>

[RazrFalcon]

Yes, the parser is for current version only.

[RazrFalcon]

Looks like we have to write a custom v0 parser, since it's way more complex than legacy and we can't simply split the name by ::.

This will also allow us to skip the disambiguation hashes.

But the format is quite complex and we can't use the rustc-demangle parser, because it stateless/recursive.

[jrmuizel]

It looks like https://github.com/michaelwoerister/std-mangle-rs is the recommended (rust-lang/rustc-demangle#28) solution to this problem.

[RazrFalcon]

Interesting. I will try it out. The only problem is how fast it would be when we need to parse thousands of names.

[RazrFalcon]

By the way, what is the difference between v0 and v2?

[RazrFalcon]

Also, look like the std-mangle-rs crate is outdated:

> cargo run -- '_RNvMs1_NtCsgE5p2UZupUb_4json5valueNtB5_9JsonValue7is_null'
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/rust-filt _RNvMs1_NtCsgE5p2UZupUb_4json5valueNtB5_9JsonValue7is_null`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: "at position 40: Expected \'C\', \'M\', \'X\', \'Y\', \'N\', \'I\', or \'B\'; found \'1\' instead; while parsing <path>"', src/libcore/result.rs:999:5

[RazrFalcon]

Done. Please test it out.

[jrmuizel]

Works great:

File  .text    Size         Crate Name
0.0%   0.7% 61.2KiB         gleam <gleam::ffi_gl::Gl>::load_with::<wrench::make_window::{closure#0}::{closure#0}>
0.0%   0.7% 61.1KiB         gleam <gleam::ffi_gl::Gl>::load_with::<wrench::make_window::{closure#1}>
0.0%   0.6% 52.5KiB        wrench <wrench::yaml_frame_writer::YamlFrameWriter>::write_display_list_items
0.0%   0.6% 47.6KiB  regex_syntax <regex_syntax::ast::parse::ParserI<&mut regex_syntax::ast::parse::Parser>>::parse_with_comments
0.0%   0.5% 40.2KiB     webrender <webrender::display_list_flattener::DisplayListFlattener>::flatten_item
0.0%   0.5% 37.5KiB        wrench <wrench::rawtest::RawtestHarness>::run
0.0%   0.5% 37.3KiB        wrench <wrench::yaml_frame_reader::YamlFrameReader>::add_display_list_items_from_yaml
0.0%   0.4% 35.1KiB        wrench wrench::main
0.0%   0.4% 34.7KiB     webrender <webrender::render_backend::RenderBackend>::process_api_msg
0.0%   0.4% 33.7KiB     webrender <webrender::renderer::Renderer>::update
0.0%   0.4% 31.3KiB     webrender <webrender::batch::BatchBuilder>::add_prim_to_batch
0.0%   0.4% 31.0KiB       inflate <inflate::InflateStream>::next_state
0.0%   0.3% 27.0KiB webrender_api <webrender_api::display_item::DebugDisplayItem as serde::ser::Serialize>::serialize::<&mut serde_json::ser::Serializer<&mut alloc::vec::Vec<u8>, serde_json::ser::PrettyFormatter>>
0.0%   0.3% 25.6KiB         winit <winit::platform::platform::x11::EventsLoop>::process_event::<&mut <winit::platform::platform::x11::EventsLoop>::run_forever<wrench::render::{closure#1}>::{closure#0}>
0.0%   0.3% 24.2KiB         image <jpeg_decoder::decoder::Decoder<std::io::buffered::BufReader<std::fs::File>>>::decode_internal
0.0%   0.3% 24.0KiB          clap <clap::app::parser::Parser>::get_matches_with::<&mut std::env::ArgsOs, std::ffi::os_str::OsString>
0.0%   0.3% 22.8KiB     webrender <webrender::renderer::Renderer>::new::{closure#2}
0.0%   0.3% 22.8KiB         gleam <gleam::ffi_gles::Gles2>::load_with::<wrench::make_window::{closure#0}::{closure#1}>
0.0%   0.3% 22.8KiB         gleam <gleam::ffi_gles::Gles2>::load_with::<wrench::make_window::{closure#2}>
0.0%   0.3% 22.5KiB         image <jpeg_decoder::decoder::Decoder<std::io::buffered::BufReader<std::fs::File>>>::decode_internal
3.4%  91.5%  7.3MiB               And 14484 smaller methods. Use -n N to show more.
3.7% 100.0%  8.0MiB               .text section size, the file size is 214.0MiB