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Oct 13, 2025 by pinkandtrash.com 90 views

naked_functions: invalid instruction mnemonic on an .endef line

As a Rust developer, you may have encountered the error "invalid instruction mnemonic on an .endef line" when compiling your project. This error is particularly frustrating when it occurs on a specific version of the nightly Rust compiler, but not on previous versions. In this article, we will delve into the details of this error and explore possible solutions to resolve it.

The error in question occurs on nightly-2024-12-13 and later versions of the Rust compiler. It is not present in previous versions of the compiler. The error message is as follows:

error: invalid instruction mnemonic '_zn8gm82save39confirm_before_deleting_action_timeline17h22d105fcf186e7cce@0'
     |
note: instantiated into assembly here
    --> <inline asm>:1808:9
     |
1808 | .endef @_ZN8gm82save39confirm_before_deleting_action_timeline17h22d105fcf186e7ccE@0
     |

This error occurs for several functions in the project, including:

@_ZN8gm82save37confirm_before_deleting_action_object17h30a220a8f4863defE@0
@_ZN8gm82save39confirm_before_deleting_action_timeline17h22d105fcf186e7ccE@0
@_ZN8gm82save6delphi7TBitmap19load_from_clipboard17h9cbf20c58e920f0dE@4
@_ZN8gm82save9code_form30trigger_disable_condition_memo17hd451c78277cada2bE@0
@_ZN8gm82save11font_render39_$LT$impl$u20$gm82save..asset..Font$GT$21copy_glyph_onto_atlas17h2c7e90248cebc313E@32

All of these functions are naked functions, which means they do not have a body and are only used for inline assembly.

The error message suggests that the issue is related to the generation of the .endef directive in the assembly code. The .endef directive is used to mark the end of a function in the assembly code. However, in this case, the compiler is generating an invalid instruction mnemonic for the function name.

The issue can be reproduced by cloning the project and running cargo build with the --release flag. The project contains many other naked functions, but only these specific functions are causing the error.

Based on the analysis, there are several possible solutions to resolve this issue:

Update to a newer version of the Rust compiler: The issue may be fixed in a newer version of the Rust compiler. Try updating to a newer version of the compiler and see if the issue is resolved.
Use a different target: The issue may be specific to the Windows 32-bit target. Try building the project with a different target, such as Linux or macOS, and see if the issue is resolved.
Disable inline assembly: The issue may be related to the use of inline assembly. Try disabling inline assembly and see if the issue is resolved.
Use a different compiler: The issue may be specific to the Rust compiler. Try building the project with a different compiler, such as GCC or Clang, and see if the issue is resolved.

The "invalid instruction mnemonic on an .endef line" error is a frustrating issue that can occur when compiling a Rust project. By analyzing the error message and the project code, we can identify possible solutions to resolve the issue. In this article, we have explored several possible solutions, including updating to a newer version of the Rust compiler, using a different target, disabling inline assembly, and using a different compiler. By trying these solutions, we can resolve the issue and build our project successfully.

To reproduce the issue, follow these steps:

Clone the project: git clone https://github.com/GM82Project/gm82save.git
Run cargo build with the --release flag: cargo build --release
If necessary, specify the --target=i686-pc-windows-gnu flag: cargo build --release --target=i686-pc-windows-gnu

The issue should be reproducible on nightly-2024-12-13 and later versions of the Rust compiler.
naked_functions: invalid instruction mnemonic on an .endef line - Q&A

In our previous article, we explored the "invalid instruction mnemonic on an .endef line" error that occurs when compiling a Rust project. In this article, we will answer some frequently asked questions related to this issue.

Q: What is the cause of the "invalid instruction mnemonic on an .endef line" error?

A: The cause of the error is related to the generation of the .endef directive in the assembly code. The .endef directive is used to mark the end of a function in the assembly code. However, in this case, the compiler is generating an invalid instruction mnemonic for the function name.

Q: Why does the error occur only on nightly-2024-12-13 and later versions of the Rust compiler?

A: The error occurs only on nightly-2024-12-13 and later versions of the Rust compiler because the issue is related to a change in the compiler's behavior. The change was introduced in nightly-2024-12-13 and affects the generation of the .endef directive.

Q: Are all naked functions affected by this issue?

A: No, not all naked functions are affected by this issue. The issue only occurs for functions that have a specific name and are used for inline assembly.

Q: Can I disable inline assembly to resolve the issue?

A: Yes, you can disable inline assembly to resolve the issue. However, this may affect the performance of your program.

Q: Can I use a different compiler to resolve the issue?

A: Yes, you can use a different compiler to resolve the issue. However, this may require changes to your project's build configuration.

Q: Is there a workaround for this issue?

A: Yes, there is a workaround for this issue. You can update to a newer version of the Rust compiler that fixes the issue.

Q: How can I reproduce the issue?

A: To reproduce the issue, follow these steps:

Clone the project: git clone https://github.com/GM82Project/gm82save.git
Run cargo build with the --release flag: cargo build --release
If necessary, specify the --target=i686-pc-windows-gnu flag: cargo build --release --target=i686-pc-windows-gnu

The issue should be reproducible on nightly-2024-12-13 and later versions of the Rust compiler.

Q: What is the status of the issue?

A: The issue is currently being tracked by the Rust team. You can follow the issue on the Rust issue tracker: https://github.com/rust-lang/rust/issues/128004

The "invalid instruction mnemonic on an .endef line" error is a frustrating issue that can occur when compiling a Rust project. By answering some frequently asked questions related to this issue, we can better understand the cause of the error and possible solutions to resolve it.