fuchsia targets building error: unresolved import object

[Wyvern]

Rust nightly: compile with -Zbuild-std and panic-immediate-abort for all fuchsia targets

unresolved import `object`
  ╭▸ /rustc/e96bb7e44fbcc23c1e6009e8d0ee8ab208668fb4/library/std/src/../../backtrace/src/print/fuchsia.rs:4:5
  │
4 │ use object::NativeEndian as NE;
  │     ━━━━━━ use of unresolved module or unlinked crate `object`
  │
  ╰ help: if you wanted to use a crate named `object`, use `cargo add object` to add it to your `Cargo.toml`

[ChrisDenton]

backtrace isn't used as a normal crate from the standard library. Instead it's built as part of std itself by using a submodule. So this would be a rust-lang/rust issue.

However, looking at std it does seem like it has an object dependency: https://github.com/rust-lang/rust/blob/798a011ace1c2b5be80767ba1d97a4dff0546f93/library/std/Cargo.toml#L41

[Wyvern]

Hmm, interesting.
I found this issue after this PR merge, #746 Bump rustc-demangle
still not sure why it happened?

[ChrisDenton]

I do not see how that could affect build-std because the standard library has its own lock file and Cargo.toml. The one in this crate isn't used.

I also tried cargo +nightly build --target x86_64-unknown-fuchsia -Z build-std with panic="immediate-abort" in Cargo.toml and it built successfully for me (rustc 1.96.0-nightly (1d8897a4e 2026-03-13)).

[Wyvern]

Found the problem, the backtrace feature is disabled for my project build, so is not pulled in automatically, which incur the following errors:

error[: unresolved import `object`
  ╭▸ /rustc/3102493c71626b5912d11d06c393b013569beb52/library/std/src/../../backtrace/src/print/fuchsia.rs:4:5
  │
4 │ use object::NativeEndian as NE;
  │     ━━━━━━ use of unresolved module or unlinked crate `object`
  │
  ╰ help: if you wanted to use a crate named `object`, use `cargo add object` to add it to your `Cargo.toml`

error[: cannot find module or crate `object` in this scope
    ╭▸ /rustc/3102493c71626b5912d11d06c393b013569beb52/library/std/src/../../backtrace/src/print/fuchsia.rs:121:17
    │
121 │ type Elf_Nhdr = object::elf::NoteHeader32<NE>;
    │                 ━━━━━━ use of unresolved module or unlinked crate `object`
    │
    ╰ help: if you wanted to use a crate named `object`, use `cargo add object` to add it to your `Cargo.toml`

error[: cannot find module or crate `object` in this scope
    ╭▸ /rustc/3102493c71626b5912d11d06c393b013569beb52/library/std/src/../../backtrace/src/print/fuchsia.rs:179:23
    │
179 │     let (out, rest) = object::pod::from_bytes::<Elf_Nhdr>(bytes).ok()?;
    │                       ━━━━━━ use of unresolved module or unlinked crate `object`
    │
    ╰ help: if you wanted to use a crate named `object`, use `cargo add object` to add it to your `Cargo.toml`

Some errors have detailed explanations: E0432, E0433.
For more information about an error, try `rustc --explain E0432`.
error: could not compile `std` (lib) due to 3 previous errors

maybe the code should be behind feature gate, such as #[cfg(feature = "backtrace")] use object::NativeEndian as NE;

cargo build -Zbuild-std=std,panic_abort -Zbuild-std-features=backtrace *-unknown-fuchsia build successfully as a workaround.