Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Stabilize #[track_caller]. #72445

Merged
merged 1 commit into from
Jul 1, 2020
Merged

Conversation

anp
Copy link
Member

@anp anp commented May 21, 2020

Stabilization Report

RFC: 2091
Tracking issue: #47809

Summary

From the rustc-dev-guide chapter:

Take this example program:

fn main() {
    let foo: Option<()> = None;
    foo.unwrap(); // this should produce a useful panic message!
}

Prior to Rust 1.42, panics like this unwrap() printed a location in libcore:

$ rustc +1.41.0 example.rs; example.exe
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value',...core\macros\mod.rs:15:40
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

As of 1.42, we get a much more helpful message:

$ rustc +1.42.0 example.rs; example.exe 
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', example.rs:3:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

These error messages are achieved through a combination of changes to panic! internals to make use of core::panic::Location::caller and a number of #[track_caller] annotations in the standard library which propagate caller information.

The attribute adds an implicit caller location argument to the ABI of annotated functions, but does not affect the type or MIR of the function. We implement the feature entirely in codegen and in the const evaluator.

Bottom Line

This PR stabilizes the use of #[track_caller] everywhere, including traits and extern blocks. It also stabilizes core::panic::Location::caller, although the use of that function in a const context remains gated by #![feature(const_caller_location)].

The implementation for the feature already changed the output of panic messages for a number of std functions, as described in the 1.42 release announcement. The attribute's use in Index and IndexMut traits is visible to users since 1.44.

Tests

All of the tests for this feature live under src/test/ui/rfc-2091-track-caller in the repo.

Noteworthy cases:

Documentation

The rustc-dev-guide now has a chapter on Implicit Caller Location.

I have an open PR to the reference documenting the attribute.

The intrinsic's wrapper includes some examples as well.

Implementation History

Unresolveds

From the RFC

Currently the RFC simply prohibit applying #[track_caller] to trait methods as a future-proofing
measure.

Resolved. See the dev-guide documentation and the tests section above.

Diverging functions should be supported.

Resolved. See the tests section above.

The closure foo::{{closure}} should inherit most attributes applied to the function foo, ...

Resolved. This unknown was related to specifics of the implementation which were made irrelevant by the final implementation.

Binary Size

I instrumented track_caller to use custom sections in a local build and discovered relatively minor binary size usage for the feature overall. I'm leaving the issue open to discuss whether we want to upstream custom section support.

There's an open issue to discuss mitigation strategies. Some decisions remain about the "right" strategies to reduce size without overly constraining the compiler implementation. I'd be excited to see someone carry that work forward but my opinion is that we shouldn't block stabilization on implementing compiler flags for redaction.

Specialization

There's an open issue on the semantics of the attribute in specialization chains. I'm inclined to move forward with stabilization without an exact resolution here given that specialization is itself unstable, but I also think it should be an easy question to resolve.

Location only points to the start of a call span

#69977 was resolved by #73182, and the next step should probably be to extend Location with a notion of the end of a call.

Regression of std's panic messages

#70963 should be resolved by serializing span hygeine to crate metadata: #68686.

@rust-highfive
Copy link
Collaborator

r? @dtolnay

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 21, 2020
@anp anp marked this pull request as ready for review May 22, 2020 00:06
@joshtriplett joshtriplett added the T-lang Relevant to the language team, which will review and decide on the PR/issue. label May 22, 2020
@joshtriplett
Copy link
Member

Looks reasonable to me.

@anp
Copy link
Member Author

anp commented May 22, 2020

Thanks! Per #47809 (comment) I think this needs T-libs as well before an FCP starts.

@rust-highfive
Copy link
Collaborator

The job x86_64-gnu-llvm-8 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.
##[section]Starting: Linux x86_64-gnu-llvm-8
##[section]Starting: Initialize job
Agent name: 'Azure Pipelines 4'
Agent machine name: 'fv-az578'
Current agent version: '2.168.2'
##[group]Operating System
16.04.6
LTS
LTS
##[endgroup]
##[group]Virtual Environment
Environment: ubuntu-16.04
Version: 20200512.2
Included Software: https://github.com/actions/virtual-environments/blob/ubuntu16/20200512.2/images/linux/Ubuntu1604-README.md
##[endgroup]
Agent running as: 'vsts'
Prepare build directory.
Set build variables.
Download all required tasks.
Download all required tasks.
Downloading task: Bash (3.163.2)
Checking job knob settings.
   Knob: AgentToolsDirectory = /opt/hostedtoolcache Source: ${AGENT_TOOLSDIRECTORY} 
   Knob: AgentPerflog = /home/vsts/perflog Source: ${VSTS_AGENT_PERFLOG} 
Start tracking orphan processes.
##[section]Finishing: Initialize job
##[section]Starting: Configure Job Name
==============================================================================
---
========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/33c70412-f4d0-4ecb-a2a8-33ff9c251cf3.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
---
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git config --get-all http.proxy
##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/72445/merge:refs/remotes/pull/72445/merge
---
 ---> cb2676f08729
Step 5/8 : ENV RUST_CONFIGURE_ARGS       --build=x86_64-unknown-linux-gnu       --llvm-root=/usr/lib/llvm-8       --enable-llvm-link-shared       --set rust.thin-lto-import-instr-limit=10
 ---> Using cache
 ---> df25ce111862
Step 6/8 : ENV SCRIPT python2.7 ../x.py test --exclude src/tools/tidy &&            python2.7 ../x.py test src/test/mir-opt --pass=build                                   --target=armv5te-unknown-linux-gnueabi &&            python2.7 ../x.py test src/tools/tidy
 ---> 599b9ac96b27
Step 7/8 : ENV NO_DEBUG_ASSERTIONS=1
 ---> Using cache
 ---> 091087e35a36
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
...........................................................................i........................ 1800/10214
.................................................................................................... 1900/10214
..............................................................................................i..i.. 2000/10214
.................................................................................................... 2100/10214
....................................................................................iiiii........... 2200/10214
.................................................................................................... 2400/10214
.................................................................................................... 2500/10214
.................................................................................................... 2600/10214
.................................................................................................... 2700/10214
---
.........i...............i.......................................................................... 5200/10214
.................................................................................................... 5300/10214
........................................................i........................................... 5400/10214
.................................................i.................................................. 5500/10214
..........................................................ii.ii........i...i........................ 5600/10214
i................................................................................................... 5800/10214
........i........................................................................................... 5900/10214
........i........................................................................................... 5900/10214
............................................................ii.F...................................i 6000/10214
.................................................................................................... 6200/10214
.................................................................................................... 6300/10214
.................................................................................................... 6300/10214
.....................ii...i..ii...........i......................................................... 6400/10214
.................................................................................................... 6600/10214
.................................................................................................... 6700/10214
.................................................................................................... 6700/10214
......................................................i..ii......................................... 6800/10214
.................................................................................................... 7000/10214
.................................................................................................... 7100/10214
........i........................................................................................... 7200/10214
.................................................................................................... 7300/10214
---
.................................................................................................... 7900/10214
.................................................................................................... 8000/10214
.................................................................................................... 8100/10214
.................................................................................................... 8200/10214
...........................................................F.F.F.F..FF.............................. 8300/10214
................................i................................................................... 8400/10214
......................................................................................iiiiii.iiiiii. 8500/10214
.........................................i.......................................................... 8700/10214
.................................................................................................... 8800/10214
.................................................................................................... 8900/10214
.................................................................................................... 9000/10214
---

---- [ui] ui/macros/issue-68060.rs stdout ----
diff of stderr:

1 error[E0658]: `#[target_feature(..)]` can only be applied to `unsafe` functions
+   --> $DIR/issue-68060.rs:4:13
3    |
3    |
4 LL |             #[target_feature(enable = "")]


11    = help: add `#![feature(target_feature_11)]` to the crate attributes to enable
13 error: the feature named `` is not valid for this target
-   --> $DIR/issue-68060.rs:6:30
+   --> $DIR/issue-68060.rs:4:30
15    |
15    |
16 LL |             #[target_feature(enable = "")]
17    |                              ^^^^^^^^^^^ `` is not valid for this target
18 
19 error[E0737]: `#[track_caller]` requires Rust ABI
-   --> $DIR/issue-68060.rs:9:13
+   --> $DIR/issue-68060.rs:7:13
+   --> $DIR/issue-68060.rs:7:13
21    |
22 LL |             #[track_caller]
23    |             ^^^^^^^^^^^^^^^


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/macros/issue-68060/issue-68060.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args macros/issue-68060.rs`
error: 1 errors occurred comparing output.
status: exit code: 1
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/macros/issue-68060.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/macros/issue-68060" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/macros/issue-68060/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0658]: `#[target_feature(..)]` can only be applied to `unsafe` functions
   |
   |
LL |             #[target_feature(enable = "")]
...
LL |             |_| (),
   |             ------ not an `unsafe` function
   |
   |
   = note: see issue #69098 <***/issues/69098> for more information
   = help: add `#![feature(target_feature_11)]` to the crate attributes to enable
error: the feature named `` is not valid for this target
  --> /checkout/src/test/ui/macros/issue-68060.rs:4:30
   |
   |
LL |             #[target_feature(enable = "")]
   |                              ^^^^^^^^^^^ `` is not valid for this target
error[E0737]: `#[track_caller]` requires Rust ABI
  --> /checkout/src/test/ui/macros/issue-68060.rs:7:13
   |
LL |             #[track_caller]
---
---- [ui] ui/rfc-2091-track-caller/const-caller-location.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rfc-2091-track-caller/const-caller-location.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/const-caller-location/a" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/const-caller-location/auxiliary"
------------------------------------------

------------------------------------------
stderr:
---
1 error: malformed `track_caller` attribute input
-   --> $DIR/error-odd-syntax.rs:3:1
+   --> $DIR/error-odd-syntax.rs:1:1
3    |
4 LL | #[track_caller(1)]
5    | ^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[track_caller]`

The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-odd-syntax/error-odd-syntax.stderr
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-odd-syntax/error-odd-syntax.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args rfc-2091-track-caller/error-odd-syntax.rs`
error: 1 errors occurred comparing output.
status: exit code: 1
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-odd-syntax" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-odd-syntax/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: malformed `track_caller` attribute input
  --> /checkout/src/test/ui/rfc-2091-track-caller/error-odd-syntax.rs:1:1
   |
LL | #[track_caller(1)]
   | ^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[track_caller]`
error: aborting due to previous error


------------------------------------------
---
11    |     ^^^^^^^^^^^^^^^


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-with-invalid-abi/error-with-invalid-abi.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args rfc-2091-track-caller/error-with-invalid-abi.rs`
error: 1 errors occurred comparing output.
status: exit code: 1
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rfc-2091-track-caller/error-with-invalid-abi.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-with-invalid-abi" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/error-with-invalid-abi/auxiliary"
------------------------------------------

------------------------------------------
stderr:
---
5    | ^^^^^^^^^^^^^^^


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/only-for-fns/only-for-fns.stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args rfc-2091-track-caller/only-for-fns.rs`
error: 1 errors occurred comparing output.
status: exit code: 1
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rfc-2091-track-caller/only-for-fns.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/only-for-fns" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/only-for-fns/auxiliary"
------------------------------------------

------------------------------------------
stderr:
---
thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-8/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "8.0.0" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
Build completed unsuccessfully in 0:56:52
Build completed unsuccessfully in 0:56:52
== clock drift check ==
  local time: Fri May 22 01:10:52 UTC 2020
  network time: Fri, 22 May 2020 01:10:52 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/72445/merge to s
Cleaning up task key
Start cleaning up orphan processes.
Terminate orphan process: pid (3938) (python)
##[section]Finishing: Finalize Job

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @rust-lang/infra. (Feature Requests)

Copy link
Member

@dtolnay dtolnay left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Reassigning for lang FCP on this thread. I made a separate libs FCP in #72448.

@dtolnay
Copy link
Member

dtolnay commented May 22, 2020

r? @joshtriplett

@joshtriplett
Copy link
Member

@dtolnay Separating the stabilizations and FCPs seems like a good idea, thank you.

For T-lang:
@rfcbot merge

@rfcbot
Copy link

rfcbot commented May 22, 2020

Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels May 22, 2020
@rust-highfive
Copy link
Collaborator

The job x86_64-gnu-llvm-8 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.
##[section]Starting: Linux x86_64-gnu-llvm-8
##[section]Starting: Initialize job
Agent name: 'Azure Pipelines 49'
Agent machine name: 'fv-az578'
Current agent version: '2.168.2'
##[group]Operating System
16.04.6
LTS
LTS
##[endgroup]
##[group]Virtual Environment
Environment: ubuntu-16.04
Version: 20200512.2
Included Software: https://github.com/actions/virtual-environments/blob/ubuntu16/20200512.2/images/linux/Ubuntu1604-README.md
##[endgroup]
Agent running as: 'vsts'
Prepare build directory.
Set build variables.
Download all required tasks.
Download all required tasks.
Downloading task: Bash (3.163.2)
Checking job knob settings.
   Knob: AgentToolsDirectory = /opt/hostedtoolcache Source: ${AGENT_TOOLSDIRECTORY} 
   Knob: AgentPerflog = /home/vsts/perflog Source: ${VSTS_AGENT_PERFLOG} 
Start tracking orphan processes.
##[section]Finishing: Initialize job
##[section]Starting: Configure Job Name
==============================================================================
---
========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/e73216d6-aae3-480f-922b-639c784c1976.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
---
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git config --get-all http.proxy
##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/72445/merge:refs/remotes/pull/72445/merge
---
 ---> cb2676f08729
Step 5/8 : ENV RUST_CONFIGURE_ARGS       --build=x86_64-unknown-linux-gnu       --llvm-root=/usr/lib/llvm-8       --enable-llvm-link-shared       --set rust.thin-lto-import-instr-limit=10
 ---> Using cache
 ---> df25ce111862
Step 6/8 : ENV SCRIPT python2.7 ../x.py test --exclude src/tools/tidy &&            python2.7 ../x.py test src/test/mir-opt --pass=build                                   --target=armv5te-unknown-linux-gnueabi &&            python2.7 ../x.py test src/tools/tidy
 ---> 599b9ac96b27
Step 7/8 : ENV NO_DEBUG_ASSERTIONS=1
 ---> Using cache
 ---> 091087e35a36
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
...........................................................................i........................ 1800/10215
.................................................................................................... 1900/10215
..............................................................................................i..i.. 2000/10215
.................................................................................................... 2100/10215
....................................................................................iiiii........... 2200/10215
.................................................................................................... 2400/10215
.................................................................................................... 2500/10215
.................................................................................................... 2600/10215
.................................................................................................... 2700/10215
---
.........i...............i.......................................................................... 5200/10215
.................................................................................................... 5300/10215
........................................................i........................................... 5400/10215
.................................................i.................................................. 5500/10215
...........................................................ii.ii........i...i....................... 5600/10215
.i.................................................................................................. 5800/10215
.........i.......................................................................................... 5900/10215
.............................................................ii..................................... 6000/10215
i................................................................................................... 6100/10215
i................................................................................................... 6100/10215
.................................................................................................... 6200/10215
.................................................................................................... 6300/10215
......................ii...i..ii...........i........................................................ 6400/10215
.................................................................................................... 6600/10215
.................................................................................................... 6700/10215
.................................................................................................... 6700/10215
.......................................................i..ii........................................ 6800/10215
.................................................................................................... 7000/10215
.................................................................................................... 7100/10215
.........i.......................................................................................... 7200/10215
.................................................................................................... 7300/10215
---
.................................................................................................... 8100/10215
.................................................................................................... 8200/10215
............................................................F....................................... 8300/10215
.................................i.................................................................. 8400/10215
.......................................................................................iiiiii.iiiiii 8500/10215
..........................................i......................................................... 8700/10215
.................................................................................................... 8800/10215
.................................................................................................... 8900/10215
.................................................................................................... 9000/10215
---
---- [ui] ui/rfc-2091-track-caller/const-caller-location.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rfc-2091-track-caller/const-caller-location.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/const-caller-location/a" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2091-track-caller/const-caller-location/auxiliary"
------------------------------------------

------------------------------------------
stderr:
---
thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:348:22
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-8/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "8.0.0" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --exclude src/tools/tidy
Build completed unsuccessfully in 1:03:40
Build completed unsuccessfully in 1:03:40
== clock drift check ==
  local time: Fri May 22 03:46:57 UTC 2020
  network time: Fri, 22 May 2020 03:46:57 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/72445/merge to s
Cleaning up task key
Start cleaning up orphan processes.
Terminate orphan process: pid (3548) (python)
##[section]Finishing: Finalize Job

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @rust-lang/infra. (Feature Requests)

@kennytm kennytm changed the title Stabilize #[(track_caller)]. Stabilize #[track_caller]. May 23, 2020
@anp anp force-pushed the stabilize-track-caller branch 2 times, most recently from e07fe26 to 47ee8d3 Compare May 23, 2020 16:13
@rust-highfive
Copy link
Collaborator

The job x86_64-gnu-llvm-8 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.
##[section]Starting: Linux x86_64-gnu-llvm-8
##[section]Starting: Initialize job
Agent name: 'Azure Pipelines 5'
Agent machine name: 'fv-az578'
Current agent version: '2.169.0'
##[group]Operating System
16.04.6
LTS
LTS
##[endgroup]
##[group]Virtual Environment
Environment: ubuntu-16.04
Version: 20200517.1
Included Software: https://github.com/actions/virtual-environments/blob/ubuntu16/20200517.1/images/linux/Ubuntu1604-README.md
##[endgroup]
Agent running as: 'vsts'
Prepare build directory.
Set build variables.
Download all required tasks.
Download all required tasks.
Downloading task: Bash (3.163.2)
Checking job knob settings.
   Knob: AgentToolsDirectory = /opt/hostedtoolcache Source: ${AGENT_TOOLSDIRECTORY} 
   Knob: AgentPerflog = /home/vsts/perflog Source: ${VSTS_AGENT_PERFLOG} 
Start tracking orphan processes.
##[section]Finishing: Initialize job
##[section]Starting: Configure Job Name
==============================================================================
---
========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/40dbfd2c-9cb8-48fe-a274-7716bf0fc628.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
---
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git config --get-all http.proxy
##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/72445/merge:refs/remotes/pull/72445/merge
---
 ---> cb2676f08729
Step 5/8 : ENV RUST_CONFIGURE_ARGS       --build=x86_64-unknown-linux-gnu       --llvm-root=/usr/lib/llvm-8       --enable-llvm-link-shared       --set rust.thin-lto-import-instr-limit=10
 ---> Using cache
 ---> df25ce111862
Step 6/8 : ENV SCRIPT python2.7 ../x.py test --exclude src/tools/tidy &&            python2.7 ../x.py test src/test/mir-opt --pass=build                                   --target=armv5te-unknown-linux-gnueabi &&            python2.7 ../x.py test src/tools/tidy
 ---> 599b9ac96b27
Step 7/8 : ENV NO_DEBUG_ASSERTIONS=1
 ---> Using cache
 ---> 091087e35a36
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
   Compiling fmt_macros v0.0.0 (/checkout/src/libfmt_macros)
   Compiling chalk-rust-ir v0.10.0
   Compiling rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
   Compiling rustc_hir v0.0.0 (/checkout/src/librustc_hir)
   Compiling rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
   Compiling chalk-solve v0.10.0
   Compiling rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
   Compiling rustc_parse v0.0.0 (/checkout/src/librustc_parse)
   Compiling rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
---
...........................................................................i........................ 1800/10217
.................................................................................................... 1900/10217
..............................................................................................i..i.. 2000/10217
.................................................................................................... 2100/10217
....................................................................................iiiii........... 2200/10217
.................................................................................................... 2400/10217
.................................................................................................... 2500/10217
.................................................................................................... 2600/10217
.................................................................................................... 2700/10217
---
.........i...............i.......................................................................... 5200/10217
.................................................................................................... 5300/10217
........................................................i........................................... 5400/10217
.................................................i.................................................. 5500/10217
...........................................................ii.ii........i...i....................... 5600/10217
.i.................................................................................................. 5800/10217
.........i.......................................................................................... 5900/10217
.............................................................ii..................................... 6000/10217
i................................................................................................... 6100/10217
i................................................................................................... 6100/10217
.................................................................................................... 6200/10217
.................................................................................................... 6300/10217
......................ii...i..ii...........i........................................................ 6400/10217
.................................................................................................... 6600/10217
.................................................................................................... 6700/10217
.................................................................................................... 6700/10217
.......................................................i..ii........................................ 6800/10217
.................................................................................................... 7000/10217
.................................................................................................... 7100/10217
.........i.......................................................................................... 7200/10217
.................................................................................................... 7300/10217
---
.................................................................................................... 8100/10217
.................................................................................................... 8200/10217
.................................................................................................... 8300/10217
..................................i................................................................. 8400/10217
........................................................................................iiiiii.iiiii 8500/10217
i.i................................................................................................. 8600/10217
.................................................................................................... 8800/10217
.................................................................................................... 8900/10217
.................................................................................................... 9000/10217
.................................................................................................... 9100/10217
---
Suite("src/test/codegen") not skipped for "bootstrap::test::Codegen" -- not in ["src/tools/tidy"]
Check compiletest suite=codegen mode=codegen (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 191 tests
iiii......i..............ii.i..........i.................................i..i................i....i. 100/191
............i.i.i...iii..iiiiiiiiiiiiiiii.......................iii................ii......

 finished in 6.277
Suite("src/test/codegen-units") not skipped for "bootstrap::test::CodegenUnits" -- not in ["src/tools/tidy"]
Check compiletest suite=codegen-units mode=codegen-units (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
---
Suite("src/test/assembly") not skipped for "bootstrap::test::Assembly" -- not in ["src/tools/tidy"]
Check compiletest suite=assembly mode=assembly (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 20 tests
iiiiiiiiiiiiiiiiiiii

 finished in 0.171
Suite("src/test/incremental") not skipped for "bootstrap::test::Incremental" -- not in ["src/tools/tidy"]
Check compiletest suite=incremental mode=incremental (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
---
Suite("src/test/debuginfo") not skipped for "bootstrap::test::Debuginfo" -- not in ["src/tools/tidy"]
Check compiletest suite=debuginfo mode=debuginfo (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 115 tests
iiiii..i.....i..i...i..i.i.i..i..i..ii....i.i....ii..........iiii.........i.....i..i.......ii.i.ii.. 100/115
...iiii.....ii.
test result: Suite("src/test/ui-fulldeps") not skipped for "bootstrap::test::UiFullDeps" -- not in ["src/tools/tidy"]

 finished in 15.975
Uplifting stage1 rustc (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Copying stage2 rustc from stage1 (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu / x86_64-unknown-linux-gnu)
---

   Doc-tests core

running 2568 tests
......iiiii......................................................................................... 100/2568
.................................................................................................ii. 200/2568
...................................i................................................................ 400/2568
.........................................................................................i..i....... 500/2568
.........................................................................................i..i....... 500/2568
...........iiii..................................................................................... 600/2568
.................................................................................................... 800/2568
.................................................................................................... 900/2568
.................................................................................................... 1000/2568
.................................................................................................... 1100/2568
---
  local time: Sat May 23 17:46:43 UTC 2020
  network time: Sat, 23 May 2020 17:46:43 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/72445/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/72445/merge to s
Cleaning up task key
Start cleaning up orphan processes.
Terminate orphan process: pid (3719) (python)
##[section]Finishing: Finalize Job

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @rust-lang/infra. (Feature Requests)

@nikomatsakis
Copy link
Contributor

Nominating just to call attention to the FCP here

Manishearth added a commit to Manishearth/rust that referenced this pull request Jul 1, 2020
Stabilize `#[track_caller]`.

# Stabilization Report

RFC: [2091]
Tracking issue: rust-lang#47809

## Summary

From the [rustc-dev-guide chapter][dev-guide]:

> Take this example program:

```rust
fn main() {
    let foo: Option<()> = None;
    foo.unwrap(); // this should produce a useful panic message!
}
```

> Prior to Rust 1.42, panics like this `unwrap()` printed a location in libcore:

```
$ rustc +1.41.0 example.rs; example.exe
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value',...core\macros\mod.rs:15:40
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
```

> As of 1.42, we get a much more helpful message:

```
$ rustc +1.42.0 example.rs; example.exe
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', example.rs:3:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

> These error messages are achieved through a combination of changes to `panic!` internals to make use of `core::panic::Location::caller` and a number of `#[track_caller]` annotations in the standard library which propagate caller information.

The attribute adds an implicit caller location argument to the ABI of annotated functions, but does not affect the type or MIR of the function. We implement the feature entirely in codegen and in the const evaluator.

## Bottom Line

This PR stabilizes the use of `#[track_caller]` everywhere, including traits and extern blocks. It also stabilizes `core::panic::Location::caller`, although the use of that function in a const context remains gated by `#![feature(const_caller_location)]`.

The implementation for the feature already changed the output of panic messages for a number of std functions, as described in the [1.42 release announcement]. The attribute's use in `Index` and `IndexMut` traits is visible to users since 1.44.

## Tests

All of the tests for this feature live under [src/test/ui/rfc-2091-track-caller][tests] in the repo.

Noteworthy cases:

* [use of attr in std]
  * validates user-facing benefit of the feature
* [trait attribute inheritance]
  * covers subtle behavior designed during implementation and not RFC'd
* [const/codegen equivalence]
  * this was the result of a suspected edge case and investigation
* [diverging function support]
  * covers an unresolved question from the RFC
* [fn pointers and shims]
  * covers important potential sources of unsoundness

## Documentation

The rustc-dev-guide now has a chapter on [Implicit Caller Location][dev-guide].

I have an [open PR to the reference][attr-reference-pr] documenting the attribute.

The intrinsic's [wrapper] includes some examples as well.

## Implementation History

* 2019-10-02: [`#[track_caller]` feature gate (RFC 2091 1/N) rust-lang#65037](rust-lang#65037)
  * Picked up the patch that @ayosec had started on the feature gate.
* 2019-10-13: [Add `Instance::resolve_for_fn_ptr` (RFC 2091 rust-lang#2/N) rust-lang#65182](rust-lang#65182)
* 2019-10-20: ~~[WIP Add MIR argument for #[track_caller] (RFC 2091 3/N) rust-lang#65258](rust-lang#65258
  * Abandoned approach to send location as a MIR argument.
* 2019-10-28: [`std::panic::Location` is a lang_item, add `core::intrinsics::caller_location` (RFC 2091 3/N) rust-lang#65664](rust-lang#65664)
* 2019-12-07: [Implement #[track_caller] attribute. (RFC 2091 4/N) rust-lang#65881](rust-lang#65881)
* 2020-01-04: [libstd uses `core::panic::Location` where possible. rust-lang#67137](rust-lang#67137)
* 2020-01-08: [`Option::{expect,unwrap}` and `Result::{expect, expect_err, unwrap, unwrap_err}` have `#[track_caller]` rust-lang#67887](rust-lang#67887)
* 2020-01-20: [Fix #[track_caller] and function pointers rust-lang#68302](rust-lang#68302) (fixed rust-lang#68178)
* 2020-03-23: [#[track_caller] in traits rust-lang#69251](rust-lang#69251)
* 2020-03-24: [#[track_caller] on core::ops::{Index, IndexMut}. rust-lang#70234](rust-lang#70234)
* 2020-04-08 [Support `#[track_caller]` on functions in `extern "Rust" { ... }` rust-lang#70916](rust-lang#70916)

## Unresolveds

### From the RFC

> Currently the RFC simply prohibit applying #[track_caller] to trait methods as a future-proofing
> measure.

**Resolved.** See the dev-guide documentation and the tests section above.

> Diverging functions should be supported.

**Resolved.** See the tests section above.

> The closure foo::{{closure}} should inherit most attributes applied to the function foo, ...

**Resolved.** This unknown was related to specifics of the implementation which were made irrelevant by the final implementation.

### Binary Size

I [instrumented track_caller to use custom sections][measure-size] in a local build and discovered relatively minor binary size usage for the feature overall. I'm leaving the issue open to discuss whether we want to upstream custom section support.

There's an [open issue to discuss mitigation strategies][mitigate-size]. Some decisions remain about the "right" strategies to reduce size without overly constraining the compiler implementation. I'd be excited to see someone carry that work forward but my opinion is that we shouldn't block stabilization on implementing compiler flags for redaction.

### Specialization

There's an [open issue][specialization] on the semantics of the attribute in specialization chains. I'm inclined to move forward with stabilization without an exact resolution here given that specialization is itself unstable, but I also think it should be an easy question to resolve.

### Location only points to the start of a call span

rust-lang#69977 was resolved by rust-lang#73182, and the next step should probably be to [extend `Location` with a notion of the end of a call](rust-lang#73554).

### Regression of std's panic messages

rust-lang#70963 should be resolved by serializing span hygeine to crate metadata: rust-lang#68686.

[2091]: https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md
[dev-guide]: https://rustc-dev-guide.rust-lang.org/codegen/implicit-caller-location.html
[specialization]: rust-lang#70293
[measure-size]: rust-lang#70579
[mitigate-size]: rust-lang#70580
[attr-reference-pr]: rust-lang/reference#742
[wrapper]: https://doc.rust-lang.org/nightly/core/panic/struct.Location.html#method.caller
[tests]: https://github.com/rust-lang/rust/tree/master/src/test/ui/rfc-2091-track-caller
[const/codegen equivalence]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/caller-location-fnptr-rt-ctfe-equiv.rs
[diverging function support]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/diverging-caller-location.rs
[use of attr in std]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/std-panic-locations.rs
[fn pointers and shims]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/tracked-fn-ptr-with-arg.rs
[trait attribute inheritance]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/tracked-trait-impls.rs
[1.42 release announcement]: https://blog.rust-lang.org/2020/03/12/Rust-1.42.html#useful-line-numbers-in-option-and-result-panic-messages
@Manishearth
Copy link
Member

5591774Z error: the feature `track_caller` has been stable since 1.46.0 and no longer requires an attribute to enable 2020-07-01T01:17:30.5592649Z --> src/librustc_save_analysis/lib.rs:4:12 2020-07-01T01:17:30.5593212Z | 2020-07-01T01:17:30.5593754Z 4 | #![feature(track_caller)] 2020-07-01T01:17:30.5594342Z | ^^^^^^^^^^^^ 2020-07-01T01:17:30.5594848Z | 2020-07-01T01:17:30.5595424Z = note: `-D stable-features` implied by `-D warn

@bors r-

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 1, 2020
Does not yet make its constness stable, though. Use of
`Location::caller` in const contexts is still gated by
`#![feature(const_caller_location)]`.
@anp
Copy link
Member Author

anp commented Jul 1, 2020

Hm, I'm confused actually. The logs point to:

 --> src/librustc_save_analysis/lib.rs:4:12
  |
4 | #![feature(track_caller)]
  |            ^^^^^^^^^^^^
  |

But I can't find that in my checkout. I rebased on top of tree and pushed again.

@Manishearth
Copy link
Member

@bors r=oli-obk delegate+

@bors
Copy link
Contributor

bors commented Jul 1, 2020

📌 Commit f07d10d has been approved by oli-obk

@bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 1, 2020
@bors
Copy link
Contributor

bors commented Jul 1, 2020

✌️ @anp can now approve this pull request

Manishearth added a commit to Manishearth/rust that referenced this pull request Jul 1, 2020
Stabilize `#[track_caller]`.

# Stabilization Report

RFC: [2091]
Tracking issue: rust-lang#47809

## Summary

From the [rustc-dev-guide chapter][dev-guide]:

> Take this example program:

```rust
fn main() {
    let foo: Option<()> = None;
    foo.unwrap(); // this should produce a useful panic message!
}
```

> Prior to Rust 1.42, panics like this `unwrap()` printed a location in libcore:

```
$ rustc +1.41.0 example.rs; example.exe
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value',...core\macros\mod.rs:15:40
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
```

> As of 1.42, we get a much more helpful message:

```
$ rustc +1.42.0 example.rs; example.exe
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', example.rs:3:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

> These error messages are achieved through a combination of changes to `panic!` internals to make use of `core::panic::Location::caller` and a number of `#[track_caller]` annotations in the standard library which propagate caller information.

The attribute adds an implicit caller location argument to the ABI of annotated functions, but does not affect the type or MIR of the function. We implement the feature entirely in codegen and in the const evaluator.

## Bottom Line

This PR stabilizes the use of `#[track_caller]` everywhere, including traits and extern blocks. It also stabilizes `core::panic::Location::caller`, although the use of that function in a const context remains gated by `#![feature(const_caller_location)]`.

The implementation for the feature already changed the output of panic messages for a number of std functions, as described in the [1.42 release announcement]. The attribute's use in `Index` and `IndexMut` traits is visible to users since 1.44.

## Tests

All of the tests for this feature live under [src/test/ui/rfc-2091-track-caller][tests] in the repo.

Noteworthy cases:

* [use of attr in std]
  * validates user-facing benefit of the feature
* [trait attribute inheritance]
  * covers subtle behavior designed during implementation and not RFC'd
* [const/codegen equivalence]
  * this was the result of a suspected edge case and investigation
* [diverging function support]
  * covers an unresolved question from the RFC
* [fn pointers and shims]
  * covers important potential sources of unsoundness

## Documentation

The rustc-dev-guide now has a chapter on [Implicit Caller Location][dev-guide].

I have an [open PR to the reference][attr-reference-pr] documenting the attribute.

The intrinsic's [wrapper] includes some examples as well.

## Implementation History

* 2019-10-02: [`#[track_caller]` feature gate (RFC 2091 1/N) rust-lang#65037](rust-lang#65037)
  * Picked up the patch that @ayosec had started on the feature gate.
* 2019-10-13: [Add `Instance::resolve_for_fn_ptr` (RFC 2091 rust-lang#2/N) rust-lang#65182](rust-lang#65182)
* 2019-10-20: ~~[WIP Add MIR argument for #[track_caller] (RFC 2091 3/N) rust-lang#65258](rust-lang#65258
  * Abandoned approach to send location as a MIR argument.
* 2019-10-28: [`std::panic::Location` is a lang_item, add `core::intrinsics::caller_location` (RFC 2091 3/N) rust-lang#65664](rust-lang#65664)
* 2019-12-07: [Implement #[track_caller] attribute. (RFC 2091 4/N) rust-lang#65881](rust-lang#65881)
* 2020-01-04: [libstd uses `core::panic::Location` where possible. rust-lang#67137](rust-lang#67137)
* 2020-01-08: [`Option::{expect,unwrap}` and `Result::{expect, expect_err, unwrap, unwrap_err}` have `#[track_caller]` rust-lang#67887](rust-lang#67887)
* 2020-01-20: [Fix #[track_caller] and function pointers rust-lang#68302](rust-lang#68302) (fixed rust-lang#68178)
* 2020-03-23: [#[track_caller] in traits rust-lang#69251](rust-lang#69251)
* 2020-03-24: [#[track_caller] on core::ops::{Index, IndexMut}. rust-lang#70234](rust-lang#70234)
* 2020-04-08 [Support `#[track_caller]` on functions in `extern "Rust" { ... }` rust-lang#70916](rust-lang#70916)

## Unresolveds

### From the RFC

> Currently the RFC simply prohibit applying #[track_caller] to trait methods as a future-proofing
> measure.

**Resolved.** See the dev-guide documentation and the tests section above.

> Diverging functions should be supported.

**Resolved.** See the tests section above.

> The closure foo::{{closure}} should inherit most attributes applied to the function foo, ...

**Resolved.** This unknown was related to specifics of the implementation which were made irrelevant by the final implementation.

### Binary Size

I [instrumented track_caller to use custom sections][measure-size] in a local build and discovered relatively minor binary size usage for the feature overall. I'm leaving the issue open to discuss whether we want to upstream custom section support.

There's an [open issue to discuss mitigation strategies][mitigate-size]. Some decisions remain about the "right" strategies to reduce size without overly constraining the compiler implementation. I'd be excited to see someone carry that work forward but my opinion is that we shouldn't block stabilization on implementing compiler flags for redaction.

### Specialization

There's an [open issue][specialization] on the semantics of the attribute in specialization chains. I'm inclined to move forward with stabilization without an exact resolution here given that specialization is itself unstable, but I also think it should be an easy question to resolve.

### Location only points to the start of a call span

rust-lang#69977 was resolved by rust-lang#73182, and the next step should probably be to [extend `Location` with a notion of the end of a call](rust-lang#73554).

### Regression of std's panic messages

rust-lang#70963 should be resolved by serializing span hygeine to crate metadata: rust-lang#68686.

[2091]: https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md
[dev-guide]: https://rustc-dev-guide.rust-lang.org/codegen/implicit-caller-location.html
[specialization]: rust-lang#70293
[measure-size]: rust-lang#70579
[mitigate-size]: rust-lang#70580
[attr-reference-pr]: rust-lang/reference#742
[wrapper]: https://doc.rust-lang.org/nightly/core/panic/struct.Location.html#method.caller
[tests]: https://github.com/rust-lang/rust/tree/master/src/test/ui/rfc-2091-track-caller
[const/codegen equivalence]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/caller-location-fnptr-rt-ctfe-equiv.rs
[diverging function support]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/diverging-caller-location.rs
[use of attr in std]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/std-panic-locations.rs
[fn pointers and shims]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/tracked-fn-ptr-with-arg.rs
[trait attribute inheritance]: https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2091-track-caller/tracked-trait-impls.rs
[1.42 release announcement]: https://blog.rust-lang.org/2020/03/12/Rust-1.42.html#useful-line-numbers-in-option-and-result-panic-messages
bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 1, 2020
…arth

Rollup of 17 pull requests

Successful merges:

 - rust-lang#72071 (Added detailed error code explanation for issue E0687 in Rust compiler.)
 - rust-lang#72369 (Bring net/parser.rs up to modern up to date with modern rust patterns)
 - rust-lang#72445 (Stabilize `#[track_caller]`.)
 - rust-lang#73466 (impl From<char> for String)
 - rust-lang#73548 (remove rustdoc warnings)
 - rust-lang#73649 (Fix sentence structure)
 - rust-lang#73678 (Update Box::from_raw example to generalize better)
 - rust-lang#73705 (stop taking references in Relate)
 - rust-lang#73716 (Document the static keyword)
 - rust-lang#73752 (Remap Windows ERROR_INVALID_PARAMETER to ErrorKind::InvalidInput from Other)
 - rust-lang#73776 (Move terminator to new module)
 - rust-lang#73778 (Make `likely` and `unlikely` const, gated by feature `const_unlikely`)
 - rust-lang#73805 (Document the type keyword)
 - rust-lang#73806 (Use an 'approximate' universal upper bound when reporting region errors)
 - rust-lang#73828 (Fix wording for anonymous parameter name help)
 - rust-lang#73846 (Fix comma in debug_assert! docs)
 - rust-lang#73847 (Edit cursor.prev() method docs in lexer)

Failed merges:

r? @ghost
@bors bors merged commit ae79c30 into rust-lang:master Jul 1, 2020
@anp anp deleted the stabilize-track-caller branch July 1, 2020 18:59
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Aug 30, 2020
according to various people on tech-pkg@, there are no problems with
the Firefox build

Version 1.46.0 (2020-08-27)
==========================

Language
--------
- [`if`, `match`, and `loop` expressions can now be used in const functions.][72437]
- [Additionally you are now also able to coerce and cast to slices (`&[T]`) in
  const functions.][73862]
- [The `#[track_caller]` attribute can now be added to functions to use the
  function's caller's location information for panic messages.][72445]
- [Recursively indexing into tuples no longer needs parentheses.][71322] E.g.
  `x.0.0` over `(x.0).0`.
- [`mem::transmute` can now be used in static and constants.][72920] **Note**
  You currently can't use `mem::transmute` in constant functions.

Compiler
--------
- [You can now use the `cdylib` target on Apple iOS and tvOS platforms.][73516]
- [Enabled static "Position Independent Executables" by default
  for `x86_64-unknown-linux-musl`.][70740]

Libraries
---------
- [`mem::forget` is now a `const fn`.][73887]
- [`String` now implements `From<char>`.][73466]
- [The `leading_ones`, and `trailing_ones` methods have been stabilised for all
  integer types.][73032]
- [`vec::IntoIter<T>` now implements `AsRef<[T]>`.][72583]
- [All non-zero integer types (`NonZeroU8`) now implement `TryFrom` for their
  zero-able equivalent (e.g. `TryFrom<u8>`).][72717]
- [`&[T]` and `&mut [T]` now implement `PartialEq<Vec<T>>`.][71660]
- [`(String, u16)` now implements `ToSocketAddrs`.][73007]
- [`vec::Drain<'_, T>` now implements `AsRef<[T]>`.][72584]

Stabilized APIs
---------------
- [`Option::zip`]
- [`vec::Drain::as_slice`]

Cargo
-----
Added a number of new environment variables that are now available when
compiling your crate.

- [`CARGO_BIN_NAME` and `CARGO_CRATE_NAME`][cargo/8270] Providing the name of
  the specific binary being compiled and the name of the crate.
- [`CARGO_PKG_LICENSE`][cargo/8325] The license from the manifest of the package.
- [`CARGO_PKG_LICENSE_FILE`][cargo/8387] The path to the license file.

Compatibility Notes
-------------------
- [The target configuration option `abi_blacklist` has been renamed
  to `unsupported_abis`.][74150] The old name will still continue to work.
- [Rustc will now warn if you cast a C-like enum that implements `Drop`.][72331]
  This was previously accepted but will become a hard error in a future release.
- [Rustc will fail to compile if you have a struct with
  `#[repr(i128)]` or `#[repr(u128)]`.][74109] This representation is currently only
  allowed on `enum`s.
- [Tokens passed to `macro_rules!` are now always captured.][73293] This helps
  ensure that spans have the correct information, and may cause breakage if you
  were relying on receiving spans with dummy information.
- [The InnoSetup installer for Windows is no longer available.][72569] This was
  a legacy installer that was replaced by a MSI installer a few years ago but
  was still being built.
- [`{f32, f64}::asinh` now returns the correct values for negative numbers.][72486]
- [Rustc will no longer accept overlapping trait implementations that only
  differ in how the lifetime was bound.][72493]
- [Rustc now correctly relates the lifetime of an existential associated
  type.][71896] This fixes some edge cases where `rustc` would erroneously allow
  you to pass a shorter lifetime than expected.
- [Rustc now dynamically links to `libz` (also called `zlib`) on Linux.][74420]
  The library will need to be installed for `rustc` to work, even though we
  expect it to be already available on most systems.
- [Tests annotated with `#[should_panic]` are broken on ARMv7 while running
  under QEMU.][74820]
- [Pretty printing of some tokens in procedural macros changed.][75453] The
  exact output returned by rustc's pretty printing is an unstable
  implementation detail: we recommend any macro relying on it to switch to a
  more robust parsing system.

[75453]: rust-lang/rust#75453
[74820]: rust-lang/rust#74820
[74420]: rust-lang/rust#74420
[74109]: rust-lang/rust#74109
[74150]: rust-lang/rust#74150
[73862]: rust-lang/rust#73862
[73887]: rust-lang/rust#73887
[73466]: rust-lang/rust#73466
[73516]: rust-lang/rust#73516
[73293]: rust-lang/rust#73293
[73007]: rust-lang/rust#73007
[73032]: rust-lang/rust#73032
[72920]: rust-lang/rust#72920
[72569]: rust-lang/rust#72569
[72583]: rust-lang/rust#72583
[72584]: rust-lang/rust#72584
[72717]: rust-lang/rust#72717
[72437]: rust-lang/rust#72437
[72445]: rust-lang/rust#72445
[72486]: rust-lang/rust#72486
[72493]: rust-lang/rust#72493
[72331]: rust-lang/rust#72331
[71896]: rust-lang/rust#71896
[71660]: rust-lang/rust#71660
[71322]: rust-lang/rust#71322
[70740]: rust-lang/rust#70740
[cargo/8270]: rust-lang/cargo#8270
[cargo/8325]: rust-lang/cargo#8325
[cargo/8387]: rust-lang/cargo#8387
[`Option::zip`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.zip
[`vec::Drain::as_slice`]: https://doc.rust-lang.org/stable/std/vec/struct.Drain.html#method.as_slice
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Oct 30, 2020
Pkgsrc changes:
 * Portability patches for Illumos have been intregrated upstream,
   so are no longer needed in pkgsrc.
 * Adjust one other patch, and update vendor/libc cargo checksum.

Upstream changes:

Version 1.46.0 (2020-08-27)
==========================

Language
--------
- [`if`, `match`, and `loop` expressions can now be used in const functions.]
  [72437]
- [Additionally you are now also able to coerce and cast to slices (`&[T]`) in
  const functions.][73862]
- [The `#[track_caller]` attribute can now be added to functions to use the
  function's caller's location information for panic messages.][72445]
- [Recursively indexing into tuples no longer needs parentheses.][71322] E.g.
  `x.0.0` over `(x.0).0`.
- [`mem::transmute` can now be used in static and constants.][72920] **Note**
  You currently can't use `mem::transmute` in constant functions.

Compiler
--------
- [You can now use the `cdylib` target on Apple iOS and tvOS platforms.][73516]
- [Enabled static "Position Independent Executables" by default
  for `x86_64-unknown-linux-musl`.][70740]

Libraries
---------
- [`mem::forget` is now a `const fn`.][73887]
- [`String` now implements `From<char>`.][73466]
- [The `leading_ones`, and `trailing_ones` methods have been stabilised for all
  integer types.][73032]
- [`vec::IntoIter<T>` now implements `AsRef<[T]>`.][72583]
- [All non-zero integer types (`NonZeroU8`) now implement `TryFrom` for their
  zero-able equivalent (e.g. `TryFrom<u8>`).][72717]
- [`&[T]` and `&mut [T]` now implement `PartialEq<Vec<T>>`.][71660]
- [`(String, u16)` now implements `ToSocketAddrs`.][73007]
- [`vec::Drain<'_, T>` now implements `AsRef<[T]>`.][72584]

Stabilized APIs
---------------
- [`Option::zip`]
- [`vec::Drain::as_slice`]

Cargo
-----
Added a number of new environment variables that are now available when
compiling your crate.

- [`CARGO_BIN_NAME` and `CARGO_CRATE_NAME`][cargo/8270] Providing the name of
  the specific binary being compiled and the name of the crate.
- [`CARGO_PKG_LICENSE`][cargo/8325] The license from the manifest of the
  package.
- [`CARGO_PKG_LICENSE_FILE`][cargo/8387] The path to the license file.

Compatibility Notes
-------------------
- [The target configuration option `abi_blacklist` has been renamed
  to `unsupported_abis`.][74150] The old name will still continue to work.
- [Rustc will now warn if you have a C-like enum that implements `Drop`.][72331]
  This was previously accepted but will become a hard error in a future release.
- [Rustc will fail to compile if you have a struct with
  `#[repr(i128)]` or `#[repr(u128)]`.][74109] This representation is currently
  only allowed on `enum`s.
- [Tokens passed to `macro_rules!` are now always captured.][73293] This helps
  ensure that spans have the correct information, and may cause breakage if you
  were relying on receiving spans with dummy information.
- [The InnoSetup installer for Windows is no longer available.][72569] This was
  a legacy installer that was replaced by a MSI installer a few years ago but
  was still being built.
- [`{f32, f64}::asinh` now returns the correct values for negative numbers.]
  [72486]
- [Rustc will no longer accept overlapping trait implementations that only
  differ in how the lifetime was bound.][72493]
- [Rustc now correctly relates the lifetime of an existential associated
  type.][71896] This fixes some edge cases where `rustc` would erroneously
  allow you to pass a shorter lifetime than expected.
- [Rustc now dynamically links to `libz` (also called `zlib`) on Linux.][74420]
  The library will need to be installed for `rustc` to work, even though we
  expect it to be already available on most systems.
- [Tests annotated with `#[should_panic]` are broken on ARMv7 while running
  under QEMU.][74820]
- [Pretty printing of some tokens in procedural macros changed.][75453] The
  exact output returned by rustc's pretty printing is an unstable
  implementation detail: we recommend any macro relying on it to switch to a
  more robust parsing system.

[75453]: rust-lang/rust#75453
[74820]: rust-lang/rust#74820
[74420]: rust-lang/rust#74420
[74109]: rust-lang/rust#74109
[74150]: rust-lang/rust#74150
[73862]: rust-lang/rust#73862
[73887]: rust-lang/rust#73887
[73466]: rust-lang/rust#73466
[73516]: rust-lang/rust#73516
[73293]: rust-lang/rust#73293
[73007]: rust-lang/rust#73007
[73032]: rust-lang/rust#73032
[72920]: rust-lang/rust#72920
[72569]: rust-lang/rust#72569
[72583]: rust-lang/rust#72583
[72584]: rust-lang/rust#72584
[72717]: rust-lang/rust#72717
[72437]: rust-lang/rust#72437
[72445]: rust-lang/rust#72445
[72486]: rust-lang/rust#72486
[72493]: rust-lang/rust#72493
[72331]: rust-lang/rust#72331
[71896]: rust-lang/rust#71896
[71660]: rust-lang/rust#71660
[71322]: rust-lang/rust#71322
[70740]: rust-lang/rust#70740
[cargo/8270]: rust-lang/cargo#8270
[cargo/8325]: rust-lang/cargo#8325
[cargo/8387]: rust-lang/cargo#8387
[`Option::zip`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.zip
[`vec::Drain::as_slice`]: https://doc.rust-lang.org/stable/std/vec/struct.Drain.html#method.as_slice
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. finished-final-comment-period The final comment period is finished for this PR / Issue. relnotes Marks issues that should be documented in the release notes of the next release. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-lang Relevant to the language team, which will review and decide on the PR/issue.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

Calling unwind via function pointer leads to odd panic message