Bevy dynamic-linking makes the program crash

[GlennFolker]

Minimal reproducible example: https://github.com/GlennFolker/cranedrop

The dynamic_linking feature flag, which converts bevy and std into a dylib for compile-time speedup, completely fails when using the Cranelift codegen backend.

System information:

• OS and arch: Windows 11, x64.
• Rustc version: rustc 1.83.0-nightly (0609062a9 2024-09-13).
• Contents of ~/.cargo/Config.toml:

  [unstable]
  codegen-backend = true
  
  [profile.dev]
  codegen-backend = "cranelift"
  incremental = true
  lto = "off"
  
  [profile.dev.package."*"]
  opt-level = 3
  
  [profile.release]
  codegen-units = 1
  incremental = false
  lto = "on"
  
  [target.x86_64-pc-windows-msvc]
  linker = "rust-lld.exe"
  rustflags = [
      "-Z", "share-generics=no",
      "-Z", "threads=0",
  ]
  

cargo run with multi_threading disabled made the program encounter a segfault:

error: process didn't exit successfully: `target\x86_64-pc-windows-msvc\debug\cranedrop.exe` (exit code: 0xc0000005, STATUS_ACCESS_VIOLATION)

cargo run with multi_threading enabled made the program panic:

thread 'main' panicked at C:\Users\glenn\.cargo\registry\src\index.crates.io-6f17d22bba15001f\bevy_tasks-0.14.2\src\task_pool.rs:186:22:
Failed to spawn thread.: Os { code: 87, kind: InvalidInput, message: "The parameter is incorrect." }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\x86_64-pc-windows-msvc\debug\cranedrop.exe` (exit code: 0xe06d7363)

[bjorn3]

cargo run with multi_threading disabled made the program encounter a segfault:

I don't use Windows, so I'm not sure I will be able to figure out what is going wrong. In any case could you please post a backtrace of the segfault?

cargo run with multi_threading enabled made the program panic:

This panic happens when trying to spawn a new thread. The error is not really informative about which parameter of the thread spawn function is incorrect.

[GlennFolker]

I tried yesterday, but I'm not sure how to GDB a Rust dynamically linked program since it complains about libbevy_dylib_<hash> and libstd_dylib_<hash> missing from the library path, and I just couldn't find them.

I'll try later today.

[GlennFolker]

Well, I couldn't figure out a way to debug the builds, but apparently x86_64-pc-windows-gnu works just fine. Error only occurs on x86_64-pc-windows-msvc.

[bjorn3]

I tried yesterday, but I'm not sure how to GDB a Rust dynamically linked program since it complains about libbevy_dylib_ and libstd_dylib_ missing from the library path, and I just couldn't find them.

You need to add both the full path to the target/x86_64-pc-windows-msvc/debug/deps dir and the path shown by rustc-clif --print target-libdir to your PATH before running the executable. Cargo and rustup together normally do this for you if you use cargo run. Also for MSVC you have to use windbg or similar as debugger. Gdb doesn't support reading debuginfo in the format MSVC uses (.pdb). Only the format unix systems use (DWARF).