[PATCH 3/5] rust: keep the build host triple out of cargo unit metadata

[sunilkumar.dora@windriver.com]

From: Sunil Dora <sunilkumar.dora@windriver.com>

cargo hashes the "host:" line of "rustc -vV" into the metadata of build
scripts and proc-macros. Every target crate that depends on one picks it
up, so the same crate gets a different -C metadata and StableCrateId on
an x86_64 and an aarch64 build host. The added patch drops the host line
from that hash.

Patch from Alejandro Enedino Hernandez Samaniego's strict-version-hash
series:
https://lists.openembedded.org/g/openembedded-core/topic/120939810

[YOCTO #16376]

Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
---
 ...-host-triple-from-unit-metadata-hash.patch | 62 +++++++++++++++++++
 meta/recipes-devtools/rust/rust-source.inc    |  1 +
 2 files changed, 63 insertions(+)
 create mode 100644 meta/recipes-devtools/rust/files/0007-cargo-omit-host-triple-from-unit-metadata-hash.patch

diff --git a/meta/recipes-devtools/rust/files/0007-cargo-omit-host-triple-from-unit-metadata-hash.patch b/meta/recipes-devtools/rust/files/0007-cargo-omit-host-triple-from-unit-metadata-hash.patch
new file mode 100644
index 0000000000..d4cb48a7a3
--- /dev/null
+++ b/meta/recipes-devtools/rust/files/0007-cargo-omit-host-triple-from-unit-metadata-hash.patch
@@ -0,0 +1,62 @@
+From 5c4fd7d8b85f4de5be387777a782fc3ddd1227d8 Mon Sep 17 00:00:00 2001
+From: Alejandro Enedino Hernandez Samaniego <alejandro@enedino.org>
+Date: Tue, 15 Sep 2026 17:05:36 +0530
+Subject: [PATCH] rust: keep the build host triple out of cargo unit metadata
+
+cargo hashes the "host:" line of "rustc -vV" into the metadata of host
+units, that is build scripts and proc-macros. Every target crate that
+depends on one picks that up through its own metadata, so the same crate
+gets a different -C metadata and StableCrateId on an x86_64 and an aarch64
+build host. Drop the host from the hash. The same class of problem is
+reported upstream, framed as OS differences, in
+https://github.com/rust-lang/cargo/issues/8140.
+
+Patch by Alejandro Enedino Hernandez Samaniego, from his strict-version-hash
+v5 series for openembedded-core:
+https://lists.openembedded.org/g/openembedded-core/topic/120939810
+
+Upstream-Status: Inappropriate [OE-specific]
+
+Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandro@enedino.org>
+Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
+---
+ .../core/compiler/build_runner/compilation_files.rs    | 10 ++--------
+ 1 file changed, 2 insertions(+), 8 deletions(-)
+
+diff --git a/src/tools/cargo/src/cargo/core/compiler/build_runner/compilation_files.rs b/src/tools/cargo/src/cargo/core/compiler/build_runner/compilation_files.rs
+index 88cab85..9dbd203 100644
+--- a/src/tools/cargo/src/cargo/core/compiler/build_runner/compilation_files.rs
++++ b/src/tools/cargo/src/cargo/core/compiler/build_runner/compilation_files.rs
+@@ -877,7 +877,7 @@ fn has_remap_path_prefix(args: &[String]) -> bool {
+ }
+ 
+ /// Hash the version of rustc being used during the build process.
+-fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher, unit: &Unit) {
++fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher, _unit: &Unit) {
+     let vers = &bcx.rustc().version;
+     if vers.pre.is_empty() || bcx.gctx.cli_unstable().separate_nightlies {
+         // For stable, keep the artifacts separate. This helps if someone is
+@@ -886,7 +886,7 @@ fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher, uni
+         // omitted since rustc should produce the same output for each target
+         // regardless of the host.
+         for line in bcx.rustc().verbose_version.lines() {
+-            if unit.kind.is_host() || !line.starts_with("host: ") {
++            if !line.starts_with("host: ") {
+                 line.hash(hasher);
+             }
+         }
+@@ -899,12 +899,6 @@ fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher, uni
+     // This assumes that the first segment is the important bit ("nightly",
+     // "beta", "dev", etc.). Skip other parts like the `.3` in `-beta.3`.
+     vers.pre.split('.').next().hash(hasher);
+-    // Keep "host" since some people switch hosts to implicitly change
+-    // targets, (like gnu vs musl or gnu vs msvc). In the future, we may want
+-    // to consider hashing `unit.kind.short_name()` instead.
+-    if unit.kind.is_host() {
+-        bcx.rustc().host.hash(hasher);
+-    }
+     // None of the other lines are important. Currently they are:
+     // binary: rustc  <-- or "rustdoc"
+     // commit-hash: 38114ff16e7856f98b2b4be7ab4cd29b38bed59a
+-- 
+2.43.0
diff --git a/meta/recipes-devtools/rust/rust-source.inc b/meta/recipes-devtools/rust/rust-source.inc
index 54502ccc9e..a294201c6e 100644
--- a/meta/recipes-devtools/rust/rust-source.inc
+++ b/meta/recipes-devtools/rust/rust-source.inc
@@ -9,6 +9,7 @@ SRC_URI += "https://static.rust-lang.org/dist/rustc-${RUST_VERSION}-src.tar.xz;n
             file://0003-bootstrap-skip-StdarchVerify-when-remote-testing.patch;patchdir=${RUSTSRC} \
             file://0004-Backport-commits-from-rust-Fix-selftest-llvm23.patch;patchdir=${RUSTSRC} \
             file://0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch;patchdir=${RUSTSRC} \
+            file://0007-cargo-omit-host-triple-from-unit-metadata-hash.patch;patchdir=${RUSTSRC} \
 "
 SRC_URI[rust.sha256sum] = "be1816e7f6c40abb90245ad6e024bed2a7e88d7dda4561e4d5470207df616b9f"
 
-- 
2.43.0