How do I add a memory address of a pointer as a span field?

[vi]

How do I do something like {:p} format as a field of a span?

tracing::field contains helpers for formatting as Debug and as Display, but I don't see the std::fmt::Pointer helper?

Ideally it should be stored as a number (without bulky allocations) and formatted as hex, just like {:p}.

[hawkw]

You can use format_args!("{:p}", ...) as a normal Debug or Display field. The format_args! macro produces a type which borrows the arguments and implements Debug and Display, rather than allocating and producing a String, like format!.

It might be worthwhile to add helper functions to tracing::field for producing dyn Displays that format something using fmt::Poitner, fmt::UpperHex/fmt::LowerHex, and other formatting traits. But, in the meantime, using format_args! should work.