winlog

A simple Rust log backend to send messages to the Windows event log.

• Writes Rust log messages to the Windows event log using the RegisterEventSourceW and ReportEventW APIs.
• Provides utility functions to register/unregister your event source in the Windows registry.
• Embeds a small (120-byte) message resource library containing the necessary log message templates in your executable.
• Does not panic.

The five Rust log levels are mapped to Windows event types as follows:

Requirements

• Rust stable (tested on 1.29)
• Windows or MinGW
• [MinGW, required] windmc and windres
• [Windows, optional] PowerShell (used for the end-to-end test)
• [Windows, optional] mc.exe and rc.exe (only required when eventmsgs.mc is changed)

Usage

Add to cargo.toml:

[dependencies]
winlog = "*"

Register the log source in the Windows registry:

winlog::register("Example Log"); // silently ignores errors
// or
winlog::try_register("Example Log").unwrap();

This usually requires Administrator permission so this is usually done during installation time. If your MSI installer (or similar) registers your event sources you should not call this.

Use the winlog backend:

winlog::init("Example Log").unwrap();
info!("Hello, Event Log");

Deregister the log source:

winlog::deregister("Example Log"); // silently ignores errors
// or
winlog::try_deregister("Example Log").unwrap();

This is usually done during program uninstall. If your MSI installer (or similar) deregisters your event sources you should not call this.

Building

Windows

cargo build --release

MinGW

Install MinGW (Ubuntu):

sudo apt install mingw-w64

Install Rust:

rustup target install x86_64-pc-windows-gnu
rustup target install i686-pc-windows-gnu

Currently the install from rustup doesn't use the correct linker so you have to add the following to .cargo/config:

[target.x86_64-pc-windows-gnu]
linker = "/usr/bin/x86_64-w64-mingw32-gcc"

[target.i686-pc-windows-gnu]
linker = "/usr/bin/i686-w64-mingw32-gcc"
rustflags = "-C panic=abort"

Build:

cargo build --release

Internals

Artifacts eventmsgs.lib and eventmsgs.rs are under source control so users don't need to have mc.exe and rc.exe installed for a standard build.

1. If build.rs determines that eventmsgs.mc was changed then build.rs:
   • invokes mc.exe (which creates eventmsgs.h)
   • invokes rc.exe (which creates eventmsgs.lib)
   • creates eventmsgs.rs from eventmsgs.h.
2. build.rs emits linker flags so eventmsgs.lib can found.
3. Standard cargo build follows.

Testing

The end-to-end test requires 'Full Control' permissions on the HKLM\SYSTEM\CurrentControlSet\Services\EventLog\Application registry key.

cargo test

Process:

1. Create a unique temporary event source name (winlog-test-###########).
2. Register our compiled test executable as EventMessageFile for the event source in the Windows registry. You can see a new key at HKLM\SYSTEM\CurrentControlSet\Services\EventLog\Application\winlog-test-###########.
3. Write some log messages to the event source.
4. Use PowerShell to retrieve the logged messages.
5. Deregister our event source. This removes the winlog-test-########### registry key.
6. Assert that the retrieved log messages are correct.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.