Add Frames Iterator for Backtrace #81022

seanchen1991 · 2021-01-14T19:52:52Z

Second attempt at adding the ability to iterate over the frames of a Backtrace by exposing the frames method.

rust-highfive · 2021-01-14T19:52:55Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Mark-Simulacrum (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

seanchen1991 · 2021-01-14T19:53:19Z

r? @KodrAus

rust-log-analyzer · 2021-01-14T20:05:54Z

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

configure: rust.channel         := nightly
configure: rust.debug-assertions := True
configure: llvm.assertions      := True
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
Checking which error codes lack tests...
Found 435 error codes
Found 0 error codes with no tests
Done!
tidy error: /checkout/library/std/src/backtrace/tests.rs:75: trailing whitespace
tidy error: /checkout/library/std/src/backtrace/tests.rs:99: trailing whitespace
tidy error: /checkout/library/std/src/backtrace.rs:159: trailing whitespace
tidy error: /checkout/library/std/src/backtrace.rs:377: trailing whitespace
tidy error: /checkout/library/std/src/backtrace.rs:517: trailing whitespace
some tidy checks failed

command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "/checkout/obj/build"
expected success, got: exit code: 1

library/std/src/backtrace.rs

KodrAus · 2021-01-16T07:32:03Z

library/std/src/backtrace.rs

@@ -147,11 +147,15 @@ fn _assert_send_sync() {
    _assert::<Backtrace>();
 }

-struct BacktraceFrame {
+/// A single frame of a backtrace.
+#[derive(Debug)]


I think we’ll probably want to implement Debug manually for this type to match the format produced by Backtrace.

Is that within scope for this PR? Or should that perhaps go in a separate one?

I think it would be within scope, since we're making this type public now.

seanchen1991 · 2021-01-19T21:20:38Z

@KodrAus I added a Debug implementation for BacktraceFrame, adhering to Backtrace's Debug impl as best I could. One question I have is in the Backtrace impl, it has

for frame in frames {
    if frame.frame.ip().is_null() {
        continue;
    }

So some frames are skipped and not printed. I'm not sure what to do in the same situation for a single BacktraceFrame. We just not print anything in that case, right?

KodrAus · 2021-01-22T04:29:20Z

Thanks @seanchen1991! This looks good to me. The main thing I was looking at with the debug format was trying to make symbols look the same.

I think we're ready to merge this! Would you be happy to squash your commits down? r=me after that.

I did have one more thought on making the return type some BacktraceFames<'a> instead of &'a [BacktraceFrame], but we can explore that asynchronously in the tracking issue.

yaahc · 2021-02-01T19:40:21Z

@bors r=KodrAus

bors · 2021-02-01T19:40:23Z

@yaahc: 🔑 Insufficient privileges: Not in reviewers

seanchen1991 · 2021-02-01T19:51:50Z

@bors r=KodrAus

bors · 2021-02-01T19:51:51Z

@seanchen1991: 🔑 Insufficient privileges: Not in reviewers

KodrAus · 2021-02-02T06:45:30Z

@bors r+

bors · 2021-02-02T06:45:31Z

📌 Commit 050643a has been approved by KodrAus

…as-schievink Rollup of 11 pull requests Successful merges: - rust-lang#80629 (Add lint for 2229 migrations) - rust-lang#81022 (Add Frames Iterator for Backtrace) - rust-lang#81481 (move some tests) - rust-lang#81485 (Add some tests for associated-type-bounds issues) - rust-lang#81492 (rustdoc: Note why `rustdoc::html::markdown` is public) - rust-lang#81577 (const_evaluatable: consider sub-expressions to be evaluatable) - rust-lang#81599 (Implement `TrustedLen` for `Fuse<I: TrustedLen>`) - rust-lang#81608 (Improve handling of spans around macro result parse errors) - rust-lang#81609 (Remove the remains of query categories) - rust-lang#81630 (Fix overflowing text on mobile when sidebar is displayed) - rust-lang#81631 (Remove unneeded `mut` variable) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

the8472 · 2021-02-07T10:45:08Z

library/std/src/backtrace.rs

+impl<'a> Backtrace {
+    /// Returns an iterator over the backtrace frames.
+    #[unstable(feature = "backtrace_frames", issue = "79676")]
+    pub fn frames(&'a self) -> &'a [BacktraceFrame] {


Wouldn't it be better if this were an iterator? That could make lazily walking the stack cheaper at some point in the future.

E.g. Java introduced a StackWalker API to make partial stack traces cheaper.

This was indeed discussed. There's some additional discussion and context that isn't apparent because it's in the previous iteration of this PR. Apologies for that.

You can read some of that discussion here.

rust-highfive assigned Mark-Simulacrum Jan 14, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 14, 2021

rust-highfive assigned KodrAus and unassigned Mark-Simulacrum Jan 14, 2021

seanchen1991 mentioned this pull request Jan 14, 2021

Tracking Issue for backtrace_frames #79676

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KodrAus reviewed Jan 15, 2021

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Add Frames iterator for Backtrace

050643a

seanchen1991 force-pushed the feat/frames-iter branch from 0023c45 to 050643a Compare January 23, 2021 17:57

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 2, 2021

jonas-schievink mentioned this pull request Feb 2, 2021

Rollup of 11 pull requests #81660

Merged

bors merged commit f61ab58 into rust-lang:master Feb 2, 2021

rustbot added this to the 1.51.0 milestone Feb 2, 2021

the8472 reviewed Feb 7, 2021

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seanchen1991 deleted the feat/frames-iter branch February 8, 2021 16:14

KodrAus mentioned this pull request Feb 11, 2021

Error Handling Project Group rust-lang/libs-team#3

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Add Frames Iterator for Backtrace #81022

Add Frames Iterator for Backtrace #81022

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Add Frames Iterator for Backtrace #81022

Add Frames Iterator for Backtrace #81022

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