Provide 32-bit and 64-bit Rust libs by default.

CC libraries which depend on Rust libraries get missing dependency
errors when building 32-bit variants dependent on Rust modules which
don't explicitly have "multilib: both" declared.

Because CC libraries use MultilibBoth by default, Rust should do the
same.

This also fixes a bug where the ARM32 toolchain incorrectly embedded
toolchain64Bit instead of toolchain32Bit.

Bug: 154730212
Test: Rust libraries provide both variants by default.
Change-Id: Ia545fe069d3c6b77c3d18f4f10267e2c72ee0bab

6 files changed, 29 insertions, 8 deletions

diff --git a/rust/builder.go b/rust/builder.go
index 27eeec23d..2d5e602ca 100644
--- a/rust/builder.go
+++ b/rust/builder.go
@@ -108,8 +108,8 @@ func transformSrctoCrate(ctx android.ModuleContext, main android.Path, deps Path
 	}
 	// TODO once we have static libraries in the host prebuilt .bp, this
 	// should be unconditionally added.
-	if !ctx.Host() {
-		// If we're on a device build, do not use an implicit sysroot
+	if !(ctx.Host() && ctx.TargetPrimary()) {
+		// If we're not targeting the host primary arch, do not use an implicit sysroot
 		rustcFlags = append(rustcFlags, "--sysroot=/dev/null")
 	}
 	// Collect linker flags
diff --git a/rust/compiler.go b/rust/compiler.go
index 81b258c1e..74997761b 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -183,8 +183,8 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 
 	if !Bool(compiler.Properties.No_stdlibs) {
 		for _, stdlib := range config.Stdlibs {
-			// If we're building for host, use the compiler's stdlibs
-			if ctx.Host() {
+			// If we're building for the primary host target, use the compiler's stdlibs
+			if ctx.Host() && ctx.TargetPrimary() {
 				stdlib = stdlib + "_" + ctx.toolchain().RustTriple()
 			}
 
@@ -192,9 +192,12 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 			// static linking is the default, if one of our static
 			// dependencies uses a dynamic library, we need to dynamically
 			// link the stdlib as well.
-			if (len(deps.Dylibs) > 0) || (!ctx.Host()) {
+			if (len(deps.Dylibs) > 0) || ctx.Device() {
 				// Dynamically linked stdlib
 				deps.Dylibs = append(deps.Dylibs, stdlib)
+			} else if ctx.Host() && !ctx.TargetPrimary() {
+				// Otherwise use the static in-tree stdlib for host secondary arch
+				deps.Rlibs = append(deps.Rlibs, stdlib+".static")
 			}
 		}
 	}
diff --git a/rust/config/arm_device.go b/rust/config/arm_device.go
index aedb42b31..ac2580b81 100644
--- a/rust/config/arm_device.go
+++ b/rust/config/arm_device.go
@@ -50,7 +50,7 @@ func init() {
 }
 
 type toolchainArm struct {
-	toolchain64Bit
+	toolchain32Bit
 	toolchainRustFlags string
 }
 
diff --git a/rust/library.go b/rust/library.go
index bf863bb67..87e816dba 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -281,7 +281,7 @@ func (library *libraryDecorator) BuildOnlyShared() {
 }
 
 func NewRustLibrary(hod android.HostOrDeviceSupported) (*Module, *libraryDecorator) {
-	module := newModule(hod, android.MultilibFirst)
+	module := newModule(hod, android.MultilibBoth)
 
 	library := &libraryDecorator{
 		MutatedProperties: LibraryMutatedProperties{
diff --git a/rust/rust_test.go b/rust/rust_test.go
index 02b190f0f..32eddc161 100644
--- a/rust/rust_test.go
+++ b/rust/rust_test.go
@@ -240,7 +240,7 @@ func TestNoStdlibs(t *testing.T) {
 		rust_binary {
 			name: "fizz-buzz",
 			srcs: ["foo.rs"],
-                        no_stdlibs: true,
+			no_stdlibs: true,
 		}`)
 	module := ctx.ModuleForTests("fizz-buzz", "android_arm64_armv8-a").Module().(*Module)
 
@@ -248,3 +248,16 @@ func TestNoStdlibs(t *testing.T) {
 		t.Errorf("no_stdlibs did not suppress dependency on libstd")
 	}
 }
+
+// Test that libraries provide both 32-bit and 64-bit variants.
+func TestMultilib(t *testing.T) {
+	ctx := testRust(t, `
+		rust_library_rlib {
+			name: "libfoo",
+			srcs: ["foo.rs"],
+			crate_name: "foo",
+		}`)
+
+	_ = ctx.ModuleForTests("libfoo", "android_arm64_armv8-a_rlib")
+	_ = ctx.ModuleForTests("libfoo", "android_arm_armv7-a-neon_rlib")
+}
diff --git a/rust/testing.go b/rust/testing.go
index c3a462553..aad4ffe35 100644
--- a/rust/testing.go
+++ b/rust/testing.go
@@ -46,24 +46,29 @@ func GatherRequiredDepsForTest() string {
 			crate_name: "std",
 			srcs: ["foo.rs"],
 			no_stdlibs: true,
+			host_supported: true,
 		}
 		rust_library_rlib {
 			name: "libstd.static",
 			crate_name: "std",
 			srcs: ["foo.rs"],
 			no_stdlibs: true,
+			host_supported: true,
 		}
 		rust_library_dylib {
 			name: "libtest",
 			crate_name: "test",
 			srcs: ["foo.rs"],
 			no_stdlibs: true,
+			host_supported: true,
+
 		}
 		rust_library_rlib {
 			name: "libtest.static",
 			crate_name: "test",
 			srcs: ["foo.rs"],
 			no_stdlibs: true,
+			host_supported: true,
 		}
 
 ` + cc.GatherRequiredDepsForTest(android.NoOsType)