fix(managed): classify 32-bit-preferred assemblies as platform neutral (#2342)

The CLI header's 32BITREQUIRED and 32BITPREFERRED bits are one two-bit
field. Reading 32BITREQUIRED on its own reported Prefer32Bit assemblies
(flags 0x00020003) as x86-only with requires_32bit true, and left
anycpu-prefer-32 reachable only through the reserved combination.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/dotnet/ManagedArtifactInspector.test.ts

@@ -292,6 +292,30 @@ describe("managed artifact inventory", () => {
     ]);
     expect(result.coverage).toMatchObject({ state: "complete", issues: [] });
   });
+
+  // dotnet/runtime corhdr.h: 32BITREQUIRED and 32BITPREFERRED form one
+  // two-bit field, so neither bit can be read on its own.
+  it.each([
+    ["neither bit", 0x0000_0001, "anycpu", false],
+    ["32BITREQUIRED alone", 0x0000_0003, "x86", true],
+    ["both bits", 0x0002_0003, "anycpu-prefer-32", false],
+    ["the reserved 32BITPREFERRED alone", 0x0002_0001, "anycpu", false],
+  ] as const)(
+    "reads %s as one 32-bit requirement",
+    (_label, cliFlags, architecture, requires32Bit) => {
+      const bytes = buildManagedPeFixture({ cliFlags });
+      const target = managedPeFixtureTarget(bytes);
+
+      expect(
+        inspectManagedArtifactBytes(bytes, target).classification
+          .managed_architecture,
+      ).toBe(architecture);
+      expect(
+        inspectManagedNativeBoundariesBytes(bytes, target).cli_native
+          ?.requires_32bit,
+      ).toBe(requires32Bit);
+    },
+  );
 });
 
 describe("managed artifact coded indexes", () => {

src/dotnet/ManagedArtifactInspector.ts

@@ -9,6 +9,7 @@ import {
   type ManagedParseIssue,
 } from "../domain/managed/managedArtifact.js";
 import {
+  managedCli32BitRequirement,
   readManagedPeLayout,
   type ManagedCliHeader,
   type ManagedPeLayout,
@@ -249,9 +250,9 @@ const managedArchitectureFor = (
 ): ManagedArtifactInspection["classification"]["managed_architecture"] => {
   if (layout.architecture !== "x86" || (cli.flags & 1) === 0)
     return layout.architecture;
-  if ((cli.flags & 0x0000_0002) !== 0) return "x86";
-  if ((cli.flags & 0x0002_0000) !== 0) return "anycpu-prefer-32";
-  return "anycpu";
+  const requirement = managedCli32BitRequirement(cli.flags);
+  if (requirement === "required") return "x86";
+  return requirement === "preferred" ? "anycpu-prefer-32" : "anycpu";
 };
 
 const runtimeClassification = ({

src/dotnet/ManagedNativeBoundaryHelpers.ts

@@ -18,7 +18,10 @@ import {
 } from "./ManagedMetadataHeaps.js";
 import { managedTableRowCounts } from "./ManagedMetadataInventory.js";
 import type { ManagedMetadataInventory } from "./ManagedMetadataInventory.js";
-import type { ManagedPeLayout } from "./ManagedPeReader.js";
+import {
+  managedCli32BitRequirement,
+  type ManagedPeLayout,
+} from "./ManagedPeReader.js";
 import { readManagedValue } from "./ManagedReaderFailure.js";
 
 type ModuleRef = ManagedNativeBoundaryInspection["module_refs"][number];
@@ -380,7 +383,7 @@ export const cliNative = (
   if (pe.cli === null) return null;
   return {
     il_only: (pe.cli.flags & 0x0000_0001) !== 0,
-    requires_32bit: (pe.cli.flags & 0x0000_0002) !== 0,
+    requires_32bit: managedCli32BitRequirement(pe.cli.flags) === "required",
     strong_name_signed: (pe.cli.flags & 0x0000_0008) !== 0,
     native_entry_point: (pe.cli.flags & 0x0000_0010) !== 0,
     ready_to_run_signature: pe.cli.readyToRunSignature,

src/dotnet/ManagedPeReader.ts

@@ -31,6 +31,20 @@ export interface ManagedCliHeader {
   readonly readyToRunSignature: boolean;
 }
 
+/**
+ * How the CLI header constrains process bitness. 32BITREQUIRED and
+ * 32BITPREFERRED are one two-bit field: required alone is x86-only, both set
+ * is platform-neutral code that prefers a 32-bit process, and preferred alone
+ * is reserved and constrains nothing.
+ */
+export const managedCli32BitRequirement = (
+  flags: number,
+): "required" | "preferred" | "none" => {
+  const pair = flags & 0x0002_0002;
+  if (pair === 0x0000_0002) return "required";
+  return pair === 0x0002_0002 ? "preferred" : "none";
+};
+
 export interface ManagedPeLayout {
   readonly machine: number;
   readonly architecture: "x86" | "x86_64" | "arm" | "arm64";