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Update book: Rust 1.77 changed the default behaviour on debug symbol stripping #13638

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Update book: Rust 1.77 changed the default behaviour on debug symbol stripping #13638

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7 changes: 4 additions & 3 deletions src/doc/src/reference/profiles.md
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Original file line number Diff line number Diff line change
Expand Up @@ -113,11 +113,12 @@ strip either symbols or debuginfo from a binary. This can be enabled like so:
# ...

[profile.release]
strip = "debuginfo"
strip = "symbols"
```

Possible string values of `strip` are `"none"`, `"debuginfo"`, and `"symbols"`.
The default is `"none"`.
For debug profiles the default is `"none"`, and for profiles with `debug = false`
the default is `"debuginfo"`.

Comment on lines 115 to 122
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Rust 1.77 changed the default behaviour on debug symbols stripping. That change seems not to be yet updated to the book, which this PR fixes.

I wonder if we need to update the documentation. The idea behind this is to emulate std respecting debug.

You can also configure this option with the boolean values `true` or `false`.
`strip = true` is equivalent to `strip = "symbols"`. `strip = false` is
Expand Down Expand Up @@ -293,7 +294,7 @@ The default settings for the `release` profile are:
opt-level = 3
debug = false
split-debuginfo = '...' # Platform-specific.
strip = "none"
strip = "debuginfo"
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This seems incorrect to me. The default value of strip for release profile is still none.

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Is strip by default will be equal to none for the release profile if debug is set to false? I read #13677, #13257, #13763, and #13638 but still didn't get it. Thanks in advance!

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The behavior of auto-stripping debuginfo is kinda dynamic. The default release profile settings is still static and strip is none when you want to inherit it.

Share these pieces of code for clarity.

cargo/src/cargo/core/profiles.rs

Lines 719 to 728 in 94aa7fb

fn default_release(trim_paths_enabled: bool) -> Profile {
let trim_paths = trim_paths_enabled.then(|| TomlTrimPathsValue::Object.into());
Profile {
name: InternedString::new("release"),
root: ProfileRoot::Release,
opt_level: InternedString::new("3"),
trim_paths,
..Profile::default()
}
}

cargo/src/cargo/core/profiles.rs

Lines 630 to 651 in 94aa7fb

impl Default for Profile {
fn default() -> Profile {
Profile {
name: InternedString::new(""),
opt_level: InternedString::new("0"),
root: ProfileRoot::Debug,
lto: Lto::Bool(false),
codegen_backend: None,
codegen_units: None,
debuginfo: DebugInfo::Resolved(TomlDebugInfo::None),
debug_assertions: false,
split_debuginfo: None,
overflow_checks: false,
rpath: false,
incremental: false,
panic: PanicStrategy::Unwind,
strip: Strip::Deferred(StripInner::None),
rustflags: vec![],
trim_paths: None,
}
}
}

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The default release profile settings is still static and strip is none when you want to inherit it.

Hmm.
According to Rust Blog:

Cargo profiles which do not enable debuginfo in outputs (e.g., debug = 0) will enable strip = "debuginfo" by default.

And according to Cargo Book:

[profile.release]
...
debug = false

I made a small test on 1.78.0 and release profile seems indeed have set strip = "debuginfo" by default.
Not sure that behaviour should be, but it seems for me also that documentation is not updated and #13677 make sense.
Or am I missing something here?
Thanks!

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See also #13638 (comment) and #13677 (comment).

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The settings are static. The actual flags passed to rustc are deferred later when Cargo see if it can safely strip std or not.

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The default is still strip=none if you turn on debug for release profile. strip=debuginfo only happens for release profile when debug is off.

But debug is off by default for the release profile, so strip="debuginfo" will take place, no? 🤔
Not sure I get it correctly, but maybe it would be great to add more context to The Cargo Book.
Thanks for the explanation!

debug-assertions = false
overflow-checks = false
lto = false
Expand Down