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fix(std): Fix undefined reference to __my_thread_exit on QNX 8.0 #144354

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Merged
merged 1 commit into from
Aug 29, 2025
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fix(std): Fix undefined reference to __my_thread_exit on QNX 8.0 #144354

merged 1 commit into from
Aug 29, 2025
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rafaeling
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@rafaeling rafaeling commented Jul 23, 2025 •
edited by rustbot
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When cross-compiling for the x86_64/aarch64-unknown-nto-qnx800 target (QNX SDP 8.0), the build fails during the final link stage with the error:

error: linking with `qcc` failed: exit status: 1
  ...
  = note: undefined reference to `__my_thread_exit'

  • On QNX 7.1: The __my_thread_exit symbol is defined and exported by the main C library (libc.a/libc.so). The std backtrace code can therefore successfully take its address at compile time.

  • On QNX 8.0: As part of a toolchain modernization, this symbol has been refactored. It is no longer present in any of the standard system libraries (.a or .so).

This patch addresses the problem at its source by conditionally compiling the problematic code.

Fixes #142726

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rustbot commented Jul 23, 2025

r? @tgross35

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 23, 2025
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@rafaeling rafaeling force-pushed the fix-142726-qnx8-link-fail branch from 58ae39f to 43fab36 Compare July 24, 2025 07:40
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This seems reasonable to me, pinging the target maintainers to make sure: @flba-eb @jonathanpallant

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flba-eb commented Jul 31, 2025 •
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In general I think this is fine. Instead of excluding QNX8.0 it could be better to only include QNX 7.0 and 7.1: If the new implementation is more modern than the previous one as @rafaeling suggests, it is likely future versions will keep the new behavior. Hence I suggest to use any(target_env = "nto70", target_env = "nto71") instead of not(target_env = "nto80").

Currently, only QNX 7.0 and 7.1 are supported by Rust (and stack unwinding probably only in 7.1).

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tgross35 commented Aug 1, 2025

To incorperate the above feedback,
@rustbot author

(please squash after)

@rustbot rustbot 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 1, 2025
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rustbot commented Aug 1, 2025

Reminder, once the PR becomes ready for a review, use @rustbot ready.

@rafaeling
fix(std): Add __my_thread_exit stub for QNX 8
17c8667 
This commit adds an empty stub for the  function
for QNX 8 targets. This symbol is required by the unwinder but is
not present, causing a linking failure when building with the
standard library.

Address review feedback: use whitelist for QNX versions
@rafaeling rafaeling force-pushed the fix-142726-qnx8-link-fail branch from 43fab36 to 17c8667 Compare August 25, 2025 08:36
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rustbot commented Aug 25, 2025

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

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rafaeling commented Aug 25, 2025 •
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@rustbot ready @flba-eb

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 25, 2025
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LGTM but I'll wait for @flba-eb to ack

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It's been a few days, seems like this is a pretty sever bug so let's get the fix in.

@bors r+ rollup

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bors commented Aug 28, 2025

📌 Commit 17c8667 has been approved by tgross35

It is now in the queue for this repository.

@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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 28, 2025
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Auto merge of #145978 - Zalathar:rollup-0dzk72g, r=Zalathar
41f2b6b 
Rollup of 9 pull requests

Successful merges:

 - #143713 (Add a mailmap entry for gnzlbg)
 - #144275 (implement Sum and Product for Saturating(u*))
 - #144354 (fix(std): Fix undefined reference to __my_thread_exit on QNX 8.0)
 - #145387 (Remove TmpLayout in layout_of_enum)
 - #145793 (std library: use execinfo library also on NetBSD.)
 - #145884 (Test `instrument-mcount` codegen)
 - #145947 (Add more to the `[workspace.dependencies]` section in the top-level `Cargo.toml`)
 - #145972 (fix `core::marker::Destruct` doc)
 - #145977 (tests: Ignore basic-stepping.rs on riscv64)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 6ac6eb6 into rust-lang:master Aug 29, 2025
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@rustbot rustbot added this to the 1.91.0 milestone Aug 29, 2025
rust-timer added a commit that referenced this pull request Aug 29, 2025
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Unrolled build for #144354
09a489d 
Rollup merge of #144354 - rafaeling:fix-142726-qnx8-link-fail, r=tgross35

fix(std): Fix undefined reference to __my_thread_exit on QNX 8.0

When cross-compiling for the x86_64/aarch64-unknown-nto-qnx800 target (QNX SDP 8.0), the build fails during the final link stage with the error:
```
error: linking with `qcc` failed: exit status: 1
  ...
  = note: undefined reference to `__my_thread_exit'
 ```

- **On QNX 7.1**: The __my_thread_exit symbol is defined and exported by the main C library (libc.a/libc.so). The std backtrace code can therefore successfully take its address at compile time.

- **On QNX 8.0**: As part of a toolchain modernization, this symbol has been refactored. It is no longer present in any of the standard system libraries (.a or .so).

This patch addresses the problem at its source by conditionally compiling the problematic code.

Fixes #142726
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Already merged.
@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 Aug 29, 2025
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[QNX] Failure to link with std on QNX 8.0
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