use an empty staticlib as an allocator library for cc_common.link

ffi/rs/allocator_library/BUILD.bazel

@@ -1,34 +1,30 @@
-load("@rules_rust//rust:defs.bzl", "rust_library")
+load("@rules_rust//rust:defs.bzl", "rust_static_library")
 
 # buildifier: disable=bzl-visibility
 load(
     "@rules_rust//rust/private:rust.bzl",
-    "rust_library_without_process_wrapper",
+    "rust_static_library_without_process_wrapper",
 )
 
 package(
     default_visibility = ["@rules_rust//ffi/rs:__subpackages__"],
 )
 
-srcs = select({
-    # Windows doesn't support weak symbol linkage.
-    # If someone can make this work on Windows, please do!
-    # For now we will silently not supply any symbols, because it would be very messy to conditionally define the default allocator library on toolchains depending on the platform.
-    "@platforms//os:windows": ["empty.rs"],
-    "//conditions:default": ["allocator_library.rs"],
-})
+# When building a staticlib crate, rustc injects the default allocator
+# redirections (e.g., __rust_alloc -> __rdl_alloc).
+# So we use an empty static library to provide these.
 
-rust_library(
+rust_static_library(
     name = "allocator_library",
-    srcs = srcs,
+    srcs = ["empty.rs"],
     allocator_libraries = "@rules_rust//ffi/rs:empty_allocator_libraries",
     edition = "2024",
     tags = ["manual"],
 )
 
-rust_library_without_process_wrapper(
+rust_static_library_without_process_wrapper(
     name = "allocator_library_without_process_wrapper",
-    srcs = srcs,
+    srcs = ["empty.rs"],
     allocator_libraries = "@rules_rust//ffi/rs:empty_allocator_libraries",
     edition = "2024",
     tags = ["manual"],

rust/private/rust.bzl

@@ -1382,6 +1382,26 @@ rust_library_without_process_wrapper = rule(
     ],
 )
 
+def _rust_static_library_without_process_wrapper_impl(ctx):
+    providers = _rust_static_library_impl(ctx)
+    return providers + [_RustBuiltWithoutProcessWrapperInfo()]
+
+rust_static_library_without_process_wrapper = rule(
+    implementation = _rust_static_library_without_process_wrapper_impl,
+    doc = "A variant of `rust_static_library` that uses a minimal process wrapper for `Rustc` actions.",
+    attrs = dict(_common_attrs_for_binary_without_process_wrapper(_common_attrs).items()),
+    fragments = ["cpp"],
+    toolchains = [
+        str(Label("//rust:toolchain_type")),
+        config_common.toolchain_type("@bazel_tools//tools/cpp:toolchain_type", mandatory = False),
+    ],
+    provides = [
+        CcInfo,
+        rust_common.test_crate_info,
+        _RustBuiltWithoutProcessWrapperInfo,
+    ],
+)
+
 def _test_attrs_for_binary_without_process_wrapper(attrs):
     new_attrs = {}
     new_attrs.update(attrs)

rust/private/rustc.bzl

@@ -1980,6 +1980,9 @@ def establish_cc_info(ctx, attr, crate_info, toolchain, cc_toolchain, feature_co
             cc_infos.append(libstd_and_allocator_cc_info)
 
     providers = [cc_common.merge_cc_infos(cc_infos = cc_infos)]
+    if crate_info.type == "staticlib":
+        # The static archive is the output.
+        dot_a = crate_info.output
     if dot_a:
         providers.append(AllocatorLibrariesImplInfo(static_archive = dot_a))
     return providers

test/integration/cc_common_link/MODULE.bazel

@@ -16,30 +16,6 @@ bazel_dep(name = "platforms", version = "1.0.0")
 rust = use_extension("@rules_rust//rust:extensions.bzl", "rust")
 rust.toolchain(
     edition = "2018",
-    target_settings = [
-        "@rules_rust//rust/settings:experimental_use_allocator_libraries_with_mangled_symbols_off",
-    ],
-)
-
-# Generate a toolchain to be used for rust-based allocator symbols.
-
-# A recent enough version of rustc that mangles the internal allocator symbols.
-VERSION = "nightly/2025-07-08"
-
-rust.repository_set(
-    name = "rust_with_alloc_mangling_linux_x86_64",
-    allocator_library = "@rules_rust//ffi/rs:empty",
-    edition = "2021",
-    exec_triple = "x86_64-unknown-linux-gnu",
-    target_compatible_with = [
-        "@platforms//cpu:x86_64",
-        "@platforms//os:linux",
-    ],
-    target_settings = [
-        "@rules_rust//rust/settings:experimental_use_allocator_libraries_with_mangled_symbols_on",
-    ],
-    target_triple = "x86_64-unknown-linux-gnu",
-    versions = [VERSION],
 )
 use_repo(rust, "rust_toolchains")