如何修复自定义属性宏中的"unsafe attribute used without unsafe"错误？

• 项目：picorv32_and_rust
• 错误代码位置：program_picorv32ec/project/src/main.rs

代码内容 #

#[picorv32asm::entry]
fn main() -> ! {
    loop {}
}

编译错误信息 #

$ cargo build
   Compiling picorv32asm v0.1.0 (/home/xiaguangbo/linux/project/custom_rv32_rust/program_picorv32ec/picorv32asm)
   Compiling project v0.1.0 (/home/xiaguangbo/linux/project/custom_rv32_rust/program_picorv32ec/project)
   Compiling picorv32entrymacro v0.1.0 (/home/xiaguangbo/linux/project/custom_rv32_rust/program_picorv32ec/picorv32asm/picorv32entrymacro)
error: unsafe attribute used without unsafe
--> src/main.rs:6:1
  |
6 | #[picorv32asm::entry]
  | ^^^^^^^^^^^^^^^^^^^^^ usage of unsafe attribute
  |
  = note: this error originates in the attribute macro `picorv32asm::entry` (in Nightly builds, run with -Z macro-backtrace for more info)
help: wrap the attribute in `unsafe(...)`
  |
6 | unsafe(#[picorv32asm::entry])
  | +++++++                     +

error: could not compile `project` (bin "project") due to 1 previous error

按照编译器提示修改为unsafe(#[picorv32asm::entry])后问题仍未解决，观察到类似WCH Rust项目可采用此类写法，特此求助解决该错误。

内容的提问来源于stack exchange，提问作者xiaguangbo