greymattergames/unbug: A crate to programmatically invoke debugging breakpoints with helping macros

A crate to programmatically invoke debugging breakpoints with helping macros.

These macros are designed to help developers catch errors during debugging sessions that would otherwise be a panic (which may not be desirable in certain contexts) or simply a log message (which may go unnoticed).

This crate’s internals are disabled by default, there are shims provided so breakpoints will not be compiled outside of a debugging context. This means that the macros in this crate can be used freely throughout your code without having to conditionally compile them out yourself.

You must use the enable feature of this crate (deactivated by default) to activate the breakpoints. This crate cannot detect the presence of a debugger.

BREAKPOINTS REQUIRE NIGHTLY RUST

BREAKPOINTS REQUIRE ENABLING THE EXPERIMENTAL core_intrinsics FEATURE

Additonally, debugging may not land on the macro statements themselves. This can have the consequence that the debgger may pause on an internal module. To avoid this, return or continue immediately following a macro invocation. Alternatively, use your debugger’s “step-out” feature until you reenter the scope of your code.

Error messages are logged when used in conjuction with Tracing

// trigger the debugger
unbug::breakpoint!();

for i in 0..5 {
    // ensure! will only trigger the debugger once
    // when the expression argument is false
    unbug::ensure!(false);
    unbug::ensure!(false, "Ensure can take an optional log message");
    unbug::ensure!(false, "{}", i);

    // ensure_always! will trigger the debugger every time
    // when the expression argument is false
    unbug::ensure_always!(i % 2 == 0);

    // Use the tracing_subscriber crate to log error messages
    // from the fail! and fail_always! macros.
    tracing_subscriber::fmt::init();

    // fail! pauses and logs an error message
    // will also only trigger once
    unbug::fail!("fail! will continue to log in non-debug builds");

    if i 3 {
        // fail! and fail_always! can be formatted just like error!
        // from the Tracing crate
        unbug::fail!("{}", i);
    }

    let Some(_out_var) = some_option else {
        unbug::fail_always!("fail_always! will trigger every time");
    };
}

Prepare your environment for debugging Rust.

If you are using VSCode you will need the Rust Analyzer and Code LLDB (Linux/Mac) or the C/C++ (Windows) extensions. See Microsoft’s Documentation on Rust Debugging in VSCode.

1. Enable Nightly Rust:

You can set a workspace toolchain override by adding a rust-toolchain.toml file at the root of your project with the following contents:

[toolchain]
channel = "nightly"

OR you can set cargo to default to nightly globally:

rustup install nightly
rustup default nightly

2. Create a debug feature in your project that will only be active in the context of a debugger, i.e. not enabled by default.

Cargo.toml:

[features]
default = []
my_debug_feature = [
    "unbug/enable"
]

3. enable the core_intrinsics feature in the root of your crate (src/main.rs or src/lib.rs)

src/main.rs:

#![cfg_attr(
    // this configuration will conditionally activate core_intrinsics
    // only when in a dev build and your debug feature is active
    all(
        debug_assertions,
        feature = "my_debug_feature",
    ),
    feature(core_intrinsics),
    // Optionally allow internal_features to suppress the warning
    allow(internal_features),
)]

4. Pass your feature flag to cargo during your debug build.

Sample VSCode .vscode/launch.json with LLDB (Linux/Mac):

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "LLDB Debug (nightly)",
            "cargo": {
                "args": [
                    "build",
                    "--bin=my_project",
                    "--package=my_project",
                    "--features=my_debug_feature"
                ],
                "filter": {
                    "name": "my_project",
                    "kind": "bin"
                }
            },
            "args": [],
            "cwd": "${workspaceFolder}",
            "env": {
                "CARGO_MANIFEST_DIR": "${workspaceFolder}"
            }
        }
    ]
}

Sample VSCode .vscode/launch.json with msvc (Windows):

{
    "version": "0.2.0",
    "configurations": [
		{
            "name": "Windows debug (nightly)",
            "type": "cppvsdbg",
            "request": "launch",
            "program": "${workspaceRoot}/target/debug/unbug_basic_example.exe",
            "stopAtEntry": false,
            "cwd": "${workspaceRoot}",
            "preLaunchTask": "win_build_debug"
        }
    ]
}

and complimentary .vscode/tasks.json

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "cargo",
			"command": "build",
			"args": [
				"--bin=my_project",
				"--package=my_project",
				"--features=my_debug_feature"
			],
			"problemMatcher": [
				"$rustc"
			],
			"group": {
				"kind": "build",
				"isDefault": true
			},
			"label": "win_build_debug"
		}
	]
}

5. Select the debug launch configuration for your platform and start debugging

In VSCode, open the “Run and Debug” panel from the left sidebar.

launch configurations can be now found in the dropdown menu next to the green “Start Debugging” button.

Unbug is free and open source. All code in this repository is dual-licensed under either:

at your option.