Missing crate attribute #[feature(maybe_uninit)

[cireu]

cargo build
    Updating `git://mirrors.ustc.edu.cn/crates.io-index` index
    Blocking waiting for file lock on package cache lock
    Blocking waiting for file lock on package cache lock
   Compiling emacs v0.10.1
error[E0658]: use of unstable library feature 'maybe_uninit'
 --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:4:5
  |
4 | use std::mem::MaybeUninit;
  |     ^^^^^^^^^^^^^^^^^^^^^
  |
  = note: for more information, see https://github.com/rust-lang/rust/issues/53491
  = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:111:26
    |
111 |         let mut symbol = MaybeUninit::uninit();
    |                          ^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:112:24
    |
112 |         let mut data = MaybeUninit::uninit();
    |                        ^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:213:22
    |
213 |         symbol: &mut MaybeUninit<emacs_value>,
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:214:20
    |
214 |         data: &mut MaybeUninit<emacs_value>,
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:120:60
    |
120 |                     symbol: unsafe { TempValue::new(symbol.assume_init()) },
    |                                                            ^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:121:56
    |
121 |                     data: unsafe { TempValue::new(data.assume_init()) },
    |                                                        ^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:128:54
    |
128 |                     tag: unsafe { TempValue::new(tag.assume_init()) },
    |                                                      ^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:129:58
    |
129 |                     value: unsafe { TempValue::new(value.assume_init()) },
    |                                                          ^^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:216:60
    |
216 |         raw_call_no_exit!(self, non_local_exit_get, symbol.as_mut_ptr(), data.as_mut_ptr())
    |                                                            ^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'maybe_uninit'
   --> /home/chino/.cargo/registry/src/mirrors.ustc.edu.cn-61ef6e0cd06fb9b8/emacs-0.10.1/src/error.rs:216:79
    |
216 |         raw_call_no_exit!(self, non_local_exit_get, symbol.as_mut_ptr(), data.as_mut_ptr())
    |                                                                               ^^^^^^^^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/53491
    = help: add #![feature(maybe_uninit)] to the crate attributes to enable

error: aborting due to 11 previous errors

[ubolonton]

I forgot that mem::MaybeUninit is new in 1.36.

Can you upgrade to Rust 1.36? If not, I'll try to revert back to mem::uninitialized for compatibility with older Rust (I prefer not to though, as it's considered UB).

[cireu]

I'am using Rust 1.36, but it still report this error.

I think the key point of this issue is the #[feature(maybe_uninit)] is needed in crate to ask rustc
enable this feature. I try to add it whether in src/lib.rs or src/error.rs, but it doesn't work.

[cireu]

Plz ignore above comment! I found I'm using 1.35 (2019-05 ver) but cargo --version reports 1.36