Binary size regression of `panic=immediate-abort` since nightly-2025-09-24

[FooIbar]

-Cpanic=immediate-abort was added in #146317 to replace -Zbuild-std-features=panic_immediate_abort.
However, we've observed a double-digit binary size regression with that:

$ cargo +nightly-2025-09-23 bloat -Zbuild-std=std,panic_abort -Zbuild-std-features=panic_immediate_abort --target $(rustc --print host-tuple) --features jvm --release --crates
[...]
 File  .text     Size Crate
15.9%  23.0%  86.5KiB core
 3.2%   4.6%  17.3KiB std
[...]

$ RUSTFLAGS="-Zunstable-options -Cpanic=immediate-abort" cargo +nightly-2025-09-24 bloat -Zbuild-std=std,panic_abort --target $(rustc --print host-tuple) --features jvm --release --crates
[...]
 File  .text     Size Crate
15.9%  21.8% 116.5KiB core
11.3%  15.5%  82.6KiB std
 5.1%   7.0%  37.4KiB gimli
 1.7%   2.3%  12.5KiB addr2line
 1.5%   2.0%  10.9KiB miniz_oxide
[...]

The size of core and std is notably increased, with gimli, miniz_oxide, and addr2line starting to show up.

@rustbot modify labels: +regression-from-stable-to-nightly -regression-untriaged

[bjorn3]

I wonder if the panic = "abort" in https://github.com/FooIbar/EhViewer/blob/085e0938cba98a5e961431660d137d492b41c54a/app/src/main/rust/Cargo.toml#L37 overrides the -Cpanic=immediate-abort.

[FooIbar]

For reference building without -Cpanic=immediate-abort:

$ cargo +nightly-2025-09-24 bloat -Zbuild-std=std,panic_abort --target $(rustc --print host-tuple) --features jvm --release --crates
[...]
 File  .text     Size Crate
15.5%  22.5% 126.2KiB core
11.2%  16.3%  91.4KiB std
 4.7%   6.8%  37.9KiB gimli
 1.5%   2.2%  12.6KiB addr2line
 1.4%   2.1%  11.8KiB miniz_oxide
[...]

Both core and std are increased, while gimli, miniz_oxide, and addr2line stay roughly the same.
It seems that -Cpanic=immediate-abort does work to some degree.

Update:

I wonder if the panic = "abort" in https://github.com/FooIbar/EhViewer/blob/085e0938cba98a5e961431660d137d492b41c54a/app/src/main/rust/Cargo.toml#L37 overrides the -Cpanic=immediate-abort.

I also tried removing the panic = "abort" but that didn't work.

[saethlin]

Where do I run those commands?

╭ ➜ ben@archlinux:/tmp/EhViewer/app/src/main/rust
╰ ➤ RUSTFLAGS="-Zunstable-options -Cpanic=immediate-abort" cargo +nightly bloat -Zbuild-std=std,panic_abort --target=aarch64-linux-android --all-features --release --crates
...
   Compiling ehviewer_rust v0.0.0 (/tmp/EhViewer/app/src/main/rust)
    Finished `release` profile [optimized] target(s) in 38.98s
Error: only 'bin', 'dylib' and 'cdylib' crate types are supported.