Use `cfg_select!` macro instead of `cfg_if!`#7636

ShaharNaveh

Since 1.95 cfg_select! macro is stabilized

https://doc.rust-lang.org/stable/std/macro.cfg_select.html

Summary by CodeRabbit

New Requirements
- Minimum supported Rust version raised to 1.95.0.
Chores
- Removed an internal build-time dependency and modernized compile-time condition handling across the codebase.
Clarification
- No changes to public APIs, runtime behavior, or platform-identifying constants; no user-facing functionality was altered.

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Reviewing files that changed from the base of the PR and between f446b28 and b4e8da6.

⛔ Files ignored due to path filters (1)

Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (1)

crates/stdlib/Cargo.toml

💤 Files with no reviewable changes (1)

crates/stdlib/Cargo.toml

📝 Walkthrough

Walkthrough

Removed cfg-if workspace dependency and replaced multiple cfg_if! conditional blocks with cfg_select! across crates; bumped workspace rust-version from 1.93.0 to 1.95.0. No public API signatures or runtime behavior were changed.

Changes

Cohort / File(s)	Summary
Workspace manifests `Cargo.toml`, `crates/common/Cargo.toml`, `crates/stdlib/Cargo.toml`, `crates/vm/Cargo.toml`	Removed `cfg-if` dependency entries from manifests; updated root/workspace `rust-version` from `1.93.0` → `1.95.0`.
Common lock logic `crates/common/src/lock.rs`	Replaced `cfg_if!` with `cfg_select!` when selecting `RawMutex`/`RawRwLock`/`RawThreadId` and `LazyLock` implementation; no API changes.
Stdlib: OpenSSL & resource `crates/stdlib/src/openssl.rs`, `crates/stdlib/src/resource.rs`	Switched OpenSSL module selection, `PROBE`/`set_default_verify_paths`, and `RLIM_NLIMITS` constant selection from `cfg_if!` to `cfg_select!` (Android `#[expect(deprecated)]` preserved).
Stdlib: socket `crates/stdlib/src/socket.rs`	Converted platform conditionals for `proto` selection and `fileno` invalid checks to `cfg_select!`; behavior unchanged.
VM manifests & concurrency impls `crates/vm/Cargo.toml`, `crates/vm/src/builtins/type.rs`	Removed `cfg-if` from vm manifest; replaced `cfg_if!` with `cfg_select!` to gate `unsafe impl Send/Sync` for `PyType`.
VM macros `crates/vm/src/macros.rs`	Unified `py_dyn_fn!` macro and used `cfg_select!` inside expansion to choose trait-object bounds (adds `Send + Sync` only when `feature = "threading"`).
VM object types `crates/vm/src/object/core.rs`, `crates/vm/src/object/ext.rs`, `crates/vm/src/object/payload.rs`	Rewrote multiple `cfg_if!`-guarded `unsafe impl Send/Sync` blocks and `PyThreadingConstraint` definition to use `cfg_select!`; semantics preserved.
VM stdlib modules `crates/vm/src/stdlib/_io.rs`, `crates/vm/src/stdlib/_signal.rs`, `crates/vm/src/stdlib/_thread.rs`, `crates/vm/src/stdlib/os.rs`, `crates/vm/src/stdlib/posix.rs`, `crates/vm/src/stdlib/sys.rs`	Replaced many platform/feature `cfg_if!` branches with `cfg_select!` for constants, type selections, and platform strings (e.g., `sys::PLATFORM` now via `cfg_select!`; `"macos"` → `"darwin"`, `"windows"` → `"win32"`).
Stdlib sqlite3/threading impls `crates/stdlib/src/_sqlite3.rs`	Replaced `cfg_if!` with `cfg_select!` around `unsafe impl Send` trait implementations; added explicit fallback arm.
Shell helper `src/shell/helper.rs`	Replaced `cfg_if!` controlling `rustyline` trait impls with `cfg_select!`, adding an explicit fallback arm for `wasm32`.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I hopped through cfg-if's tangled lair,
swapped branches neat with cfg_select flair.
Same shapes, same bounds, one tiny version leap—
I nibble old macros, then cuddle up to sleep. 🥕✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: replacing `cfg_if!` conditional compilation with `cfg_select!` macro throughout the codebase.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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coderabbitai

Actionable comments posted: 3

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

crates/vm/src/stdlib/posix.rs (1)

1805-1820: ⚠️ Potential issue | 🔴 Critical

Remove the stray if from the cfg_select! arm.

Line 1807 uses if any(...) =>, but Rust 1.95 cfg_select! arms use the cfg predicate directly without the if keyword (any(...) =>). This is a compile-blocking syntax error. All other cfg_select! usages in the codebase follow the correct syntax without if.

🐛 Proposed fix

                 // Note: POSIX_SPAWN_SETSID may not be available on all platforms
                 cfg_select! {
-                    if any(
+                    any(
                         target_os = "linux",
                         target_os = "haiku",
                         target_os = "solaris",
                         target_os = "illumos",
                         target_os = "hurd",
                     ) => {
                         flags.insert(nix::spawn::PosixSpawnFlags::from_bits_retain(libc::POSIX_SPAWN_SETSID));

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@crates/vm/src/stdlib/posix.rs` around lines 1805 - 1820, The cfg_select! arm
in the flags handling block incorrectly uses the `if` keyword ("if any(...) =>")
which is invalid syntax; edit the cfg_select! invocation (the block that inserts
nix::spawn::PosixSpawnFlags::from_bits_retain(libc::POSIX_SPAWN_SETSID) and
returns a new_not_implemented_error) to remove the stray `if` so the arm uses
the predicate directly (e.g., `any(...) =>`), leaving the flags.insert(...) and
the `_ => { return Err(vm.new_not_implemented_error(...)); }` arm unchanged.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/stdlib/src/openssl.rs`:
- Around line 35-42: The PROBE static initializer's cfg_select! branches end
with trailing semicolons making each branch evaluate to () instead of returning
a LazyLock<ProbeResult>; remove the semicolons after
LazyLock::new(openssl_probe::probe) and LazyLock::new(|| ProbeResult {
cert_file: None, cert_dir: vec![] }) so each branch yields a
LazyLock<ProbeResult> (affecting the PROBE static, the cfg_select! macro,
LazyLock::new invocations, and the ProbeResult construction).

In `@crates/vm/src/stdlib/_thread.rs`:
- Around line 34-39: The cfg_select! arms for PYTHREAD_NAME currently list the
broader unix => Some("pthread") arm before the more specific any(target_os =
"solaris", target_os = "illumos") arm, so Solaris/illumos targets never reach
their intended match; fix by reordering the cfg_select! arms in the
PYTHREAD_NAME constant so the any(target_os = "solaris", target_os = "illumos")
arm appears before the unix arm, preserving the other arms (windows and default)
as-is.

In `@crates/vm/src/stdlib/sys.rs`:
- Around line 248-255: The PLATFORM constant in sys.rs currently maps target_os
"macos" and Windows to non-CPython values; update the cfg_select! mapping in the
pub const PLATFORM definition so that target_os = "macos" => "darwin" and
windows => "win32" (leave the other arms unchanged) to match CPython's
sys.platform values; modify the PLATFORM const in crates/vm/src/stdlib/sys.rs
accordingly and run the build/tests to verify.

---

Outside diff comments:
In `@crates/vm/src/stdlib/posix.rs`:
- Around line 1805-1820: The cfg_select! arm in the flags handling block
incorrectly uses the `if` keyword ("if any(...) =>") which is invalid syntax;
edit the cfg_select! invocation (the block that inserts
nix::spawn::PosixSpawnFlags::from_bits_retain(libc::POSIX_SPAWN_SETSID) and
returns a new_not_implemented_error) to remove the stray `if` so the arm uses
the predicate directly (e.g., `any(...) =>`), leaving the flags.insert(...) and
the `_ => { return Err(vm.new_not_implemented_error(...)); }` arm unchanged.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between af41d11 and 67f5ebc.

⛔ Files ignored due to path filters (1)

Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (19)

Cargo.toml
crates/common/Cargo.toml
crates/common/src/lock.rs
crates/stdlib/Cargo.toml
crates/stdlib/src/openssl.rs
crates/stdlib/src/resource.rs
crates/stdlib/src/socket.rs
crates/vm/Cargo.toml
crates/vm/src/builtins/type.rs
crates/vm/src/macros.rs
crates/vm/src/object/core.rs
crates/vm/src/object/ext.rs
crates/vm/src/object/payload.rs
crates/vm/src/stdlib/_io.rs
crates/vm/src/stdlib/_signal.rs
crates/vm/src/stdlib/_thread.rs
crates/vm/src/stdlib/os.rs
crates/vm/src/stdlib/posix.rs
crates/vm/src/stdlib/sys.rs

💤 Files with no reviewable changes (3)

crates/common/Cargo.toml
crates/vm/Cargo.toml
crates/stdlib/Cargo.toml

coolreader18

LGTM

ShaharNaveh force-pushed the cfg-select-macro branch from 67f5ebc to 8db3293 Compare April 20, 2026 13:12

ShaharNaveh marked this pull request as draft April 20, 2026 13:16

coderabbitai Bot reviewed Apr 20, 2026

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ShaharNaveh force-pushed the cfg-select-macro branch 9 times, most recently from 8169811 to 7dce1bb Compare April 20, 2026 17:03

Use cfg_select!

f446b28

ShaharNaveh force-pushed the cfg-select-macro branch from 7dce1bb to f446b28 Compare April 20, 2026 18:17

ShaharNaveh marked this pull request as ready for review April 20, 2026 19:23

ShaharNaveh requested a review from youknowone April 21, 2026 07:21

youknowone approved these changes Apr 21, 2026

View reviewed changes

youknowone enabled auto-merge (squash) April 21, 2026 15:03

coolreader18 approved these changes Apr 21, 2026

View reviewed changes

Merge remote-tracking branch 'upstream/main' into cfg-select-macro

b4e8da6

coolreader18 mentioned this pull request Apr 30, 2026

Use cfg_select in a bunch more places #7740

Merged

coderabbitai Bot mentioned this pull request Jun 18, 2026

host_env: os.mkdir for Windows, Redox #8128

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Use `cfg_select!` macro instead of `cfg_if!`#7636