Macro dbg 

macro_rules! dbg {
    () => { ... };
    ($val:expr $(,)?) => { ... };
    ($($val:expr),+ $(,)?) => { ... };
}

Prints and returns the value of a given expression for quick and dirty debugging.

Similar to [std::dbg], except it:

• Writes atomically, up to the greatest length supported on the platform.
• Doesn’t use locks (in userspace).
• Preserve libc’s errno and Windows’ last-error code value.

This allows it to be used to debug allocators, multi-threaded code, synchronization routines, startup code, and more.