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chore(deps): pull portable-atomic only where it is reachable #18

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Merged
Ttimmahlax merged 1 commit into from
Sep 8, 2026
+16 −2
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chore(deps): pull portable-atomic only where it is reachable #18

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18 changes: 16 additions & 2 deletions crates/rusty_alloc/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,17 @@ readme = "README.md"
# mimalloc's `mi_deferred_free_fun`. Narrowing either breaks a contract, and
# hand-rolling a 64-bit atomic out of two 32-bit halves inside an allocator is
# exactly the kind of thing that produces a subtle bug.
#
# `optional`, and enabled by `std` rather than by the target alone. The use site
# is gated `all(not(target_has_atomic = "64"), feature = "std")` -- a `no_std`
# build uses `options::split64` instead -- so a firmware was fetching and
# compiling a crate it then discarded at link time. Zero bytes on the device
# either way (verified: after `split64` landed, `portable_atomic` symbols in a
# shipped ESP32 image went to zero and its 4,288-byte `LOCKS` table left the
# symbol map), but an unused crate still shows up in an SBOM, a `cargo audit`
# and every dependency count a firmware reviewer looks at.
[target.'cfg(not(target_has_atomic = "64"))'.dependencies]
portable-atomic = { version = "1", default-features = false, features = ["fallback"] }
portable-atomic = { version = "1", default-features = false, features = ["fallback"], optional = true }

[features]
# `std` is DEFAULT and additive — unlike the geometry `--cfg` (P2), which is
Expand All @@ -35,7 +44,12 @@ portable-atomic = { version = "1", default-features = false, features = ["fallba
# single-heap profile: no `thread_local!`, no environment, no `process::abort`
# (see `lib.rs`). P3 of docs/plans/small-metal.md.
default = ["std"]
std = []
# Pulls `portable-atomic` ONLY where it is actually reachable: a target without
# 64-bit atomics that also has `std`. On every other target the dependency is
# not in the graph at all -- the `dep:` reference resolves against a
# target-gated declaration, so it simply does not apply where the target section
# does not match.
std = ["dep:portable-atomic"]
# Full invariant checking: list walks, canaries, double-free detection (our `dmi`).
debug_checks = []
# Feature-gated rdtsc path profiler (§7.5 of the plan). OFF = byte-identical build.
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