Affirm `-Cforce-frame-pointers=off` does not override #140774

workingjubilee · 2025-05-07T21:47:22Z

This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in #86652 that defies the expectations of some programmers. Some programmers believe -Cforce-frame-pointers=false should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding.

T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the -Cforce-frame-pointers option, is not required, even if =off is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers

We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

bjorn3 · 2025-05-07T22:52:15Z

The current behavior of being a ratchet makes most sense to me. Enabling force-frame-pointers forces frame pointers to be used, disabling it is equivalent to not passing it at all and causes the default to be used. This matches the behavior of force-unwind-tables (for which the current behavior is required. disabling unwind tables when they are enabled by default is unsound and picking the target default even when force-unwind-tables is enabled makes the cli option useless)

Noratrieb · 2025-05-08T06:12:12Z

I agree and think the naming conveys this as well. The absence of force should not force the opposite, it just leaves it up to the compiler to choose.

In fact, this is already clearly documented: https://doc.rust-lang.org/rustc/codegen-options/index.html?highlight=force-frame#force-frame-pointers

n, no, off or false: do not force-enable frame pointers. This does not necessarily mean frame pointers will be removed.

And this documentation has been there basically forever: #65136

workingjubilee · 2025-05-08T19:38:37Z

Yes. This is essentially me looking for a clarification that yes, we intended to head in this direction, to make sure I have something authoritative to point to if it comes up again and help inform any near-future decisions about frame-pointer-related things.

apiraino · 2025-05-22T16:01:56Z

Discussed durint T-compiler triage on Zulip.

We agree the situation with this multiple-value boolean flag is awkward. Maybe updating the documentation (comment) could alleviate this confusion.

We are in favor of accepting this patch! Thanks for raising the topic.

@rustbot label -I-compiler-nominated

apiraino · 2025-05-29T09:50:01Z

I guess the next step is getting someone review this - right?

@workingjubilee please proceed with this work (if you need to) of feel free to ask for a review

@rustbot author

This test only makes sense if you send it back in time and run it with a now-old Rust commit, e.g. 50e0cc5 However, if you do go back that far in time, you will see it pass.

workingjubilee · 2025-06-04T22:56:14Z

Yes, I'm indecisive sometimes.

r? compiler

…pointers-favor-the-target-or-cli, r=jieyouxu Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in rust-lang#86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

Rollup of 11 pull requests Successful merges: - #140774 (Affirm `-Cforce-frame-pointers=off` does not override) - #141001 (Make NonZero<char> possible) - #141700 (Atomic intrinsics : use const generic ordering, part 2) - #142008 (const-eval error: always say in which item the error occurred) - #142053 (Add new Tier-3 targets: `loongarch32-unknown-none*`) - #142089 (Replace all uses of sysroot_candidates with get_or_default_sysroot) - #142108 (compiler: Add track_caller to AbiMapping::unwrap) - #142132 (`tests/ui`: A New Order [6/N]) - #142162 (UnsafePinned: update get() docs and signature to allow shared mutation) - #142171 (`tests/ui`: A New Order [7/N]) - #142179 (store `target.min_global_align` as an `Align`) r? `@ghost` `@rustbot` modify labels: rollup

workingjubilee · 2025-06-08T20:00:48Z

hurr
@bors r-

workingjubilee · 2025-06-17T06:56:14Z

@bors2 try jobs=test-various

rust-bors · 2025-06-17T06:56:18Z

⌛ Trying commit 5a449fb with merge 9ca9e59…

To cancel the try build, run the command @bors2 try cancel.

…vor-the-target-or-cli, r=<try> Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in #86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything. try-job: test-various

rust-bors · 2025-06-17T08:21:27Z

☀️ Try build successful (CI)
Build commit: 9ca9e59 (9ca9e593391be5f0d36a3713e358f418d16ba1fe, parent: 55d436467c351b56253deeba209ae2553d1c243f)

workingjubilee · 2025-06-17T23:12:24Z

Effectively a minor spelling error in the codegen test (some platforms can add dso_local).

@bors r=jieyouxu

bors · 2025-06-17T23:12:27Z

📌 Commit 5a449fb has been approved by jieyouxu

It is now in the queue for this repository.

…pointers-favor-the-target-or-cli, r=jieyouxu Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in rust-lang#86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

Rollup of 10 pull requests Successful merges: - #135656 (Add `-Z hint-mostly-unused` to tell rustc that most of a crate will go unused) - #138237 (Get rid of `EscapeDebugInner`.) - #140772 ({aarch64,x86_64}-pc-windows-gnullvm: build host tools) - #140774 (Affirm `-Cforce-frame-pointers=off` does not override) - #141610 (Stabilize `feature(generic_arg_infer)`) - #141864 (Handle win32 separator for cygwin paths) - #142384 (Bringing `rustc_rayon_core` in tree as `rustc_thread_pool`) - #142502 (rustdoc_json: improve handling of generic args) - #142571 (Reason about borrowed classes in CopyProp.) - #142591 (Add spawn APIs for BootstrapCommand to support deferred command execution) r? `@ghost` `@rustbot` modify labels: rollup

…pointers-favor-the-target-or-cli, r=jieyouxu Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in rust-lang#86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

Rollup of 12 pull requests Successful merges: - #135656 (Add `-Z hint-mostly-unused` to tell rustc that most of a crate will go unused) - #140774 (Affirm `-Cforce-frame-pointers=off` does not override) - #141610 (Stabilize `feature(generic_arg_infer)`) - #142123 (Implement initial support for timing sections (`--json=timings`)) - #142383 (CodeGen: rework Aggregate implemention for rvalue_creates_operand cases) - #142502 (rustdoc_json: improve handling of generic args) - #142591 (Add spawn APIs for BootstrapCommand to support deferred command execution) - #142606 (AsyncDrop trait without sync Drop generates an error) - #142619 (apply clippy::or_fun_call) - #142624 (Actually take `--build` into account in bootstrap) - #142627 (Add `StepMetadata` to describe steps) - #142660 (remove joboet from review rotation) r? `@ghost` `@rustbot` modify labels: rollup

…pointers-favor-the-target-or-cli, r=jieyouxu Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in rust-lang#86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

Rollup of 11 pull requests Successful merges: - #140774 (Affirm `-Cforce-frame-pointers=off` does not override) - #141610 (Stabilize `feature(generic_arg_infer)`) - #142383 (CodeGen: rework Aggregate implemention for rvalue_creates_operand cases) - #142591 (Add spawn APIs for BootstrapCommand to support deferred command execution) - #142619 (apply clippy::or_fun_call) - #142624 (Actually take `--build` into account in bootstrap) - #142627 (Add `StepMetadata` to describe steps) - #142660 (remove joboet from review rotation) - #142666 (Skip tidy triagebot linkcheck if `triagebot.toml` doesn't exist) - #142672 (Clarify bootstrap tools description) - #142674 (remove duplicate crash test) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #140774 - workingjubilee:should-force-frame-pointers-favor-the-target-or-cli, r=jieyouxu Affirm `-Cforce-frame-pointers=off` does not override This PR exists to document that we (that is, the compiler reviewer) implicitly made a decision in #86652 that defies the expectations of some programmers. Some programmers believe `-Cforce-frame-pointers=false` should obey the programmer in all cases, forcing the compiler to avoid generating frame pointers, even if the target specification would indicate they must be generated. However, many targets rely on frame pointers for fast or sound unwinding. T-compiler had a weekly triage meeting on 2025-05-22. This topic was put to discussion because some programmers may expect the target-overriding behavior. In that meeting we decided removing frame pointers, at least with regards to the contract of the `-Cforce-frame-pointers` option, is not required, even if `=off` is passed, and that we will not do so if the target would expect them. This follows from the documentation here: https://doc.rust-lang.org/rustc/codegen-options/index.html#force-frame-pointers We may separately pursue trying to clarify the situation more emphatically in our documentation, or warn when people pass the option when it doesn't do anything.

Rollup of 11 pull requests Successful merges: - rust-lang/rust#140774 (Affirm `-Cforce-frame-pointers=off` does not override) - rust-lang/rust#141610 (Stabilize `feature(generic_arg_infer)`) - rust-lang/rust#142383 (CodeGen: rework Aggregate implemention for rvalue_creates_operand cases) - rust-lang/rust#142591 (Add spawn APIs for BootstrapCommand to support deferred command execution) - rust-lang/rust#142619 (apply clippy::or_fun_call) - rust-lang/rust#142624 (Actually take `--build` into account in bootstrap) - rust-lang/rust#142627 (Add `StepMetadata` to describe steps) - rust-lang/rust#142660 (remove joboet from review rotation) - rust-lang/rust#142666 (Skip tidy triagebot linkcheck if `triagebot.toml` doesn't exist) - rust-lang/rust#142672 (Clarify bootstrap tools description) - rust-lang/rust#142674 (remove duplicate crash test) r? `@ghost` `@rustbot` modify labels: rollup

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Enable non-leaf Frame Pointers for Arm64 Windows #140828

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codegen: test frame pointer attr prefers CLI opt

f27ed88

This test only makes sense if you send it back in time and run it with a now-old Rust commit, e.g. 50e0cc5 However, if you do go back that far in time, you will see it pass.

workingjubilee force-pushed the should-force-frame-pointers-favor-the-target-or-cli branch from aaa10fe to e05c680 Compare June 4, 2025 21:51

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workingjubilee force-pushed the should-force-frame-pointers-favor-the-target-or-cli branch 2 times, most recently from 59c6fb8 to 4d62cab Compare June 4, 2025 22:48

workingjubilee changed the title ~~Should -Cforce-frame-pointers favor the target or CLI?~~ Decide -Cforce-frame-pointers favors the target Jun 4, 2025

workingjubilee changed the title ~~Decide -Cforce-frame-pointers favors the target~~ Affirm -Cforce-frame-pointers=off does not override Jun 4, 2025

workingjubilee changed the title ~~Affirm -Cforce-frame-pointers=off does not override~~ compiler: affirm -Cforce-frame-pointers=off does not override Jun 4, 2025

workingjubilee changed the title ~~compiler: affirm -Cforce-frame-pointers=off does not override~~ Affirm -Cforce-frame-pointers=off does not override Jun 4, 2025

rustbot assigned jieyouxu Jun 4, 2025

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Rollup of 11 pull requests #142195

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tests: remove define so dso_local attr does not disrupt test

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Rollup of 10 pull requests #142656

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