Build Error: Cannot resolve `uefi::prelude::*` items (SystemTable, println!, etc.) and `#[entry]` macro issues with v0.35.0 on nightly"

[deepm1nd]

Describe the bug
When attempting to build a minimal UEFI application using uefi-rs v0.35.0 on a recent nightly Rust toolchain (specifically targeting x86_64-unknown-uefi with -Zbuild-std for core and compiler_builtins), basic items from uefi::prelude::* (such as println!, SystemTable, Boot, image_handle(), system_table()) are not found by the compiler. Additionally, the #[entry] macro seems to have issues:

• If efi_main is defined to take Handle and SystemTable<Boot> arguments (as per documentation), the build fails with "Entry function must have no arguments".
• If efi_main is defined to take no arguments (and attempts to use the free functions image_handle() and system_table()), it fails because those functions (and other prelude items) are not found.

This issue is reproducible in a minimal example and also blocks a more complex project.

Environment:

• uefi-rs version: 0.35.0
• Rust toolchain: nightly (specifically 1.89.0-nightly (be19eda0d 2025-06-22) as per build log, though the rust-toolchain.toml just specifies nightly)
• Target: x86_64-unknown-uefi
• Build host OS (if relevant, this is a sandboxed environment): Linux-based
• build-std configuration: build-std = ["core", "compiler_builtins"] with build-std-features = ["compiler-builtins-mem"]

To Reproduce
Steps to reproduce the behavior:

1. Set up the following minimal project structure and files:

   uefi_minimal_test/Cargo.toml

   [package]
   name = "uefi_minimal_test"
   version = "0.1.0"
   edition = "2021"
   
   [dependencies]
   uefi = { version = "0.35.0", features = ["logger", "panic_handler"] }
   
   [profile.dev]
   panic = "abort"
   
   [profile.release]
   panic = "abort"

   uefi_minimal_test/.cargo/config.toml

   [unstable]
   build-std = ["core", "compiler_builtins"]
   build-std-features = ["compiler-builtins-mem"]
   
   [build]
   target = "x86_64-unknown-uefi"

   uefi_minimal_test/rust-toolchain.toml

   [toolchain]
   channel = "nightly"

   uefi_minimal_test/src/main.rs (this version has efi_main() taking no arguments)

   #![no_std]
   #![no_main]
   
   use core::panic::PanicInfo; 
   use uefi::prelude::*;
   
   #[entry]
   fn efi_main() -> Status { 
       let _image_handle = match image_handle() {
           Ok(h) => h,
           Err(_e) => {
               return Status::LOAD_ERROR;
           }
       };
       let st_ptr = match system_table() {
           Ok(ptr) => ptr,
           Err(_e) => {
               return Status::LOAD_ERROR;
           }
       };
       let mut _system_table = unsafe { SystemTable::<Boot>::from_ptr(st_ptr).unwrap() };
       
       println!("Hello from UEFI Minimal Test!");
       
       loop {
           unsafe { core::arch::asm!("pause") };
       }
   }
   
   // Panic handler is provided by the "panic_handler" feature of the `uefi` crate.
   /*
   #[panic_handler]
   fn panic(_info: &PanicInfo) -> ! {
       loop {}
   }
   */

2. Ensure the target and rust-src are installed:

   rustup target add x86_64-unknown-uefi
   rustup component add rust-src --toolchain nightly 

   (These steps were performed in the environment)

3. Run the build command from the directory containing uefi_minimal_test (e.g., /app if uefi_minimal_test is in /app):

   cargo +nightly build --manifest-path uefi_minimal_test/Cargo.toml --target x86_64-unknown-uefi 

   (Or cd uefi_minimal_test && cargo +nightly build --target x86_64-unknown-uefi)

Expected behavior
The minimal application should compile successfully. If efi_main takes arguments, #[entry] should handle it. If efi_main takes no arguments, items from uefi::prelude::* like println!, image_handle(), system_table(), SystemTable, Boot should be resolved.

Actual behavior
The build fails with errors indicating that items from uefi::prelude::* cannot be found.

Full Build Log:

Compiling uefi_minimal_test v0.1.0 (/app/uefi_minimal_test)
error: cannot find macro `println` in this scope
  --> src/main.rs:26:5
   |
26 |     println!("Hello from UEFI Minimal Test!"); // Use prelude's println
   |     ^^^^^^^
   |
help: consider importing this macro
   |
4  + use uefi::println;
   |

error[E0425]: cannot find function `image_handle` in this scope
  --> src/main.rs:11:31
   |
11 |     let _image_handle = match image_handle() {
   |                               ^^^^^^^^^^^^ not found in this scope
   |
help: consider importing one of these functions
   |
4  + use crate::boot::image_handle;
   |
4  + use uefi::boot::image_handle;
   |

error[E0412]: cannot find type `Boot` in this scope
  --> src/main.rs:24:52
   |
24 |     let mut _system_table = unsafe { SystemTable::<Boot>::from_ptr(st_ptr).unwrap() };
   |                                                    ^^^^ not found in this scope
   |
help: you might be missing a type parameter
   |
8  | fn efi_main<Boot>() -> Status { // No arguments
   |            ++++++

warning: unused import: `core::panic::PanicInfo`
 --> src/main.rs:4:5
  |
4 | use core::panic::PanicInfo;
  |     ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

error[E0425]: cannot find function `system_table` in this scope
  --> src/main.rs:18:24
   |
18 |     let st_ptr = match system_table() {
   |                        ^^^^^^^^^^^^ not found in this scope

error[E0433]: failed to resolve: use of undeclared type `SystemTable`
  --> src/main.rs:24:38
   |
24 |     let mut _system_table = unsafe { SystemTable::<Boot>::from_ptr(st_ptr).unwrap() };
   |                                      ^^^^^^^^^^^ use of undeclared type `SystemTable`

Some errors have detailed explanations: E0412, E0425, E0433.
For more information about an error, try `rustc --explain E0412`.
warning: `uefi_minimal_test` (bin "uefi_minimal_test") generated 1 warning
error: could not compile `uefi_minimal_test` (bin "uefi_minimal_test") due to 5 previous errors; 1 warning emitted
If src/main.rs is changed so efi_main takes _image_handle: Handle, mut system_table: SystemTable<Boot> arguments, the error changes to: error: Entry function must have no arguments

Additional context

This issue was encountered while trying to set up a more complex kernel project (torux), and the minimal example was created to isolate the problem. The torux project experiences the same uefi module/item resolution failures.
The torux project also consistently fails with "no global memory allocator found but one is required", even with a #[global_allocator] defined and extern crate alloc;. This error also appears in the minimal example if alloc types are used and uefi = { features = ["alloc"]} is enabled alongside build-std = [..., "alloc"]. For the provided minimal example, alloc usage was removed to focus on the prelude/entry macro issue.
The problem persists across various attempts to configure build-std (with/without "alloc") and uefi crate features.
The cargo tree for the minimal example (and the more complex project) shows uefi v0.35.0 as a direct dependency.
Any guidance on what might be causing this apparent failure to resolve standard uefi-rs prelude items and #[entry] macro behavior would be greatly appreciated.

[nicholasbishop]

As was noted here, it would be much better to link to a small git repo that reproduces the issue. You've written a lot of text which makes it hard to see the actual problem. I wonder if perhaps you are using one of those genai tools? If so, I'd recommend you stop doing that, and read the crate documentation instead. I promise it'll give you vastly better info than an LLM :)

If efi_main takes no arguments, items from uefi::prelude::* like println!, image_handle(), system_table(), SystemTable, Boot should be resolved.

Indeed efi_main should take no arguments, this is documented in the entry macro.

See also the documentation for the prelude module. As you can see, image_handle, system_table, SystemTable, and Boot are not listed there. The latter two types were removed a while ago, see API migration: Deprecating SystemTable/BootServices/RuntimeServices.

The image_handle function is here: https://docs.rs/uefi/latest/uefi/boot/fn.image_handle.html.

For the system table, use the functions in uefi::system, or use uefi::table::system_table_raw if you need access to the raw pointer.

General suggestions: read the documentation, read the compiler errors, and make sure you take the time to understand what documentation and compiler output are saying (an LLM can't do this work for you, you have to take the time to understand it yourself.)

[deepm1nd]

Sorry, I used the LLM to write my issue because of my poor last showing. Won't do that again. I got the earlier 0.30 version working, but abandoned that after this advice.

But....your advice did the trick,
The API Migration guide was the key! I missed that, and the uefi-rs book doc has conflicting (maybe it just confused me) info on parameters for efi_main coming from #[entry]. The test now compiles. Thanks!

Looks like i was premature and looked at an older result. I'll try again and report back.