trace 0.0.2

trace

A syntax extension for tracing the execution of functions. Adding #[trace] to the top of any function will insert println! statements at the beginning and end of that function, notifying you of when that function was entered and exited. This is useful for quickly debugging whether functions that are supposed to be called are actually called without manually inserting print statements.

Note that this currently only works on individual functions. Support for impls and mods is in the works, but individual impl methods can't be supported due to limitations of the syntax extension system.

Installation

Add trace = "*" to your Cargo.toml.

Example

Here is an example you can find in the examples folder. If you've cloned the project, you can run this with cargo run --example example.

#![feature(custom_attribute, plugin)]
#![plugin(trace)]

static mut depth: u32 = 0;

fn main() {
    foo();
}

#[trace]
fn foo() {
    println!("I'm in foo!");
    bar();
}

#[trace(prefix_enter="[ENTER]", prefix_exit="[EXIT]")]
fn bar() {
    println!("I'm in bar!");
}

Output:

[+] Entering foo
I'm in foo!
 [ENTER] Entering bar
I'm in bar!
 [EXIT] Exiting bar
[-] Exiting foo

Note that you can customize the prefix of the println! statement with prefix_enter and prefix_exit. The depth variable must be a global static mut variable, it's used for indenting the output.