project: https://github.com/xiaguangbo/picorv32_and_rust
error code：
program_picorv32ec/project/src/main.rs
#[picorv32asm::entry]
fn main() -> ! {
loop {}
}
error message：
$ 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
It doesn't work either if you follow the compiler's prompts.
I think other projects can also be written like this, such as wch rust project.
Your #[picorv32asm::entry] macro generates from this:
quote!(
#[export_name = "main"]
fn main() -> ! {
#(#stmts)*
}
)
In the Rust 2024 edition, certain attributes were marked unsafe and you must wrap them in unsafe(...) to use them. #[export_name = ...] was one of those due to the possibility of global name conflicts. And since macros expand within the local crate, the error tries to suggest a fix there which won't work since you can't modify the macro output (directly).
One solution as you show is to use an earlier edition in the local crate. Deleting edition = ... altogether will mean it defaults to 2015 but you'd likely be better served by 2018 or 2021.
The other option is to update your macro to produce the new syntax.
#[unsafe(export_name = "main")]