taproot-primitives: Correctly gate alloc on alloc feature
What the developer wrote
Authored by Mitchell Bagot
taproot-primitives: Correctly gate alloc on alloc feature
At the moment, the taproot-primitives crate always externs alloc,
even for no-alloc builds. This means that certain alloc types are
used even for no-alloc builds, which will break builds that actually
have no alloc available.
Correctly gate alloc extern behind alloc feature and gate macro
invocations that require alloc.
What changed, and why it matters
This is a build-system fix for a Rust crate that supports both memory-allocator and no-allocator environments. The crate was always pulling in the standard memory allocator even when a user explicitly requested a no-allocator build, which would cause compilation to fail on platforms without an allocator. The patch simply adds the correct on/off switch so the allocator is only used when the corresponding feature is enabled. There is no runtime security vulnerability or exploit here.
No security action required. Treat as a normal build-fix release; update if your project builds taproot-primitives without the alloc feature.
Security signals we found
No security signal: build configuration bug only
No unsafe code, no input parsing, no cryptographic operations changed
Compile-time failure in no-alloc configurations, not a runtime vulnerability
Evidence from the diff
In taproot-primitives/src/lib.rs, the extern crate alloc; declaration and two invocations of internals::impl_to_hex_from_lower_hex! are now gated behind #[cfg(feature = “alloc”)]. Previously these were unconditional, so a no-alloc build (–no-default-features without alloc) would still reference alloc types and macros requiring alloc, resulting in a compile-time failure. The change is purely a feature-gating correction; no cryptographic, consensus, or runtime logic is modified.
Changed components
taproot-primitives/src/lib.rsno-alloc / --no-default-features builds of taproot-primitivesInspect captured patch +3 / −0
diff --git a/taproot-primitives/src/lib.rs b/taproot-primitives/src/lib.rs
index 9375d3f5..1dc5a05d 100644
--- a/taproot-primitives/src/lib.rs
+++ b/taproot-primitives/src/lib.rs
@@ -13,6 +13,7 @@
#![allow(clippy::manual_range_contains)] // More readable than clippy's format.
#![allow(clippy::uninlined_format_args)] // Allow `format!("{}", x)` instead of enforcing `format!("{x}")`
+#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(feature = "std")]
@@ -190,6 +191,7 @@ impl fmt::LowerHex for LeafVersion {
fmt::LowerHex::fmt(&self.to_consensus(), f)
}
}
+#[cfg(feature = "alloc")]
internals::impl_to_hex_from_lower_hex!(LeafVersion, |_| 2);
impl fmt::UpperHex for LeafVersion {
@@ -281,6 +283,7 @@ impl fmt::LowerHex for FutureLeafVersion {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { fmt::LowerHex::fmt(&self.0, f) }
}
+#[cfg(feature = "alloc")]
internals::impl_to_hex_from_lower_hex!(FutureLeafVersion, |_| 2);
impl fmt::UpperHex for FutureLeafVersion {
Why this scored 17/100
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