util: add track_caller to public APIs #4785
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Functions that may panic can be annotated with `#[track_caller]` so that in the event of a panic, the function where the user called the panicking function is shown instead of the file and line within Tokio source. This change adds `#[track_caller]` to all the non-unstable public APIs in tokio-util where the documentation describes how the function may panic due to incorrect context or inputs. In one place, an assert was added where the described behavior appeared not to be implemented. The documentation for `DelayQueue::reserve` states that the function will panic if the new capacity exceeds the maximum number of entries the queue can contain. However, the function didn't panic until a higher number caused by an allocation failure. This is inconsistent with `DelayQueue::insert_at` which will panic if the number of entries were to go over MAX_ENTRIES. Tests are included to cover each potentially panicking function. Refs: tokio-rs#4413
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This PR is marked as a draft. Please let me know when you would like it to be reviewed, and if you have any other questions. |
Some tests were failing on FreeBSD 32-bit because the "times too far in the future" for DelayQueue were also too far in the future for the OS. Fixed by copying the MAX_DURATION value from where it's defined and using it to create a duration that is just 1 more than the maximum. This will start to break once we get close (within 2 and a bit years) of the Epochalypse (19 Jan, 2038) - but a lot of other things are going to be breaking on FreeBSD 32-bit by then anyway.
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@Darksonn It's ready now. I realized that I had some broken tests on FreeBSD 32-bit and marked the PR a draft until I could fix them as I wasn't sure how complicated it was going to be. Thanks for your help! |
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Motivation
When a user of tokio calls a function that panics when misused (e.g. calling
DelayQueue::insert_atwith a an instant 100 years in the future) then the usercurrently sees the line number of the panic call inside tokio. It would be more
informative for the user to see the place where they called the panicking function.
It is still possible for the user to see the full stack trace by setting the
environment variable RUST_BACKLOG=1, so no useful information is
hidden.
This change is the second step in closing #4413 (after #4772), this change
is for the tokio-util crate.
Note that there was an earlier PR (#4445) to work on this issue for the tokio-util
crate, but it hasn't seen much work recently and after looking into it, I found that
these change in the main crate are necessary prerequisites.
Solution
Functions that may panic can be annotated with
#[track_caller]so thatin the event of a panic, the function where the user called the
panicking function is shown instead of the file and line within Tokio
source.
This change adds
#[track_caller]to all the non-unstable public APIs intokio-util where the documentation describes how the function may panic
due to incorrect context or inputs.
In one place, an assert was added where the described behavior appeared
not to be implemented. The documentation for
DelayQueue::reservestates that the function will panic if the new capacity exceeds the
maximum number of entries the queue can contain. However, the function
didn't panic until a higher number caused by an allocation failure. This
is inconsistent with
DelayQueue::insert_atwhich will panic if thenumber of entries were to go over MAX_ENTRIES.
Tests are included to cover each potentially panicking function.
Refs: #4413