Build Rust Device Sysroots in Soong

In order to ensure we are using current platform Bionic for any platform
Rust binaries, we need to build the sysroot in Soong. This will also
enable us too hook the "test" crate if necessary.

While both a dynamic and static sysroot are available, on device only a
dynamic sysroot will be injected. On host, we continue using the sysroot
used to build the compiler as before.

Bug: 139486496
Change-Id: I127377e5b056610ceb5015a34d266250320fbc31

rust/binary.go

@@ -16,7 +16,6 @@ package rust
 
 import (
 	"android/soong/android"
-	"android/soong/rust/config"
 )
 
 func init() {
@@ -89,12 +88,6 @@ func (binary *binaryDecorator) compilerFlags(ctx ModuleContext, flags Flags) Fla
 func (binary *binaryDecorator) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps = binary.baseCompiler.compilerDeps(ctx, deps)
 
-	if binary.preferDynamic() || len(deps.Dylibs) > 0 {
-		for _, stdlib := range config.Stdlibs {
-			deps.Dylibs = append(deps.Dylibs, stdlib+"_"+ctx.toolchain().RustTriple())
-		}
-	}
-
 	if ctx.toolchain().Bionic() {
 		deps = binary.baseCompiler.bionicDeps(ctx, deps)
 		deps.CrtBegin = "crtbegin_dynamic"

rust/builder.go

@@ -93,6 +93,12 @@ func transformSrctoCrate(ctx android.ModuleContext, main android.Path,
 		rustcFlags = append(rustcFlags, "--target="+targetTriple)
 		linkFlags = append(linkFlags, "-target "+targetTriple)
 	}
+	// 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
+		rustcFlags = append(rustcFlags, "--sysroot=/dev/null")
+	}
 	// Collect linker flags
 	linkFlags = append(linkFlags, flags.GlobalLinkFlags...)
 	linkFlags = append(linkFlags, flags.LinkFlags...)

rust/compiler.go

@@ -31,6 +31,10 @@ func getDenyWarnings(compiler *baseCompiler) bool {
 	return BoolDefault(compiler.Properties.Deny_warnings, config.DefaultDenyWarnings)
 }
 
+func (compiler *baseCompiler) setNoStdlibs() {
+	compiler.Properties.No_stdlibs = proptools.BoolPtr(true)
+}
+
 func NewBaseCompiler(dir, dir64 string) *baseCompiler {
 	return &baseCompiler{
 		Properties: BaseCompilerProperties{},
@@ -81,6 +85,9 @@ type BaseCompilerProperties struct {
 
 	// install to a subdirectory of the default install path for the module
 	Relative_install_path *string `android:"arch_variant"`
+
+	// whether to suppress inclusion of standard crates - defaults to false
+	No_stdlibs *bool
 }
 
 type baseCompiler struct {
@@ -160,6 +167,23 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps.StaticLibs = append(deps.StaticLibs, compiler.Properties.Static_libs...)
 	deps.SharedLibs = append(deps.SharedLibs, compiler.Properties.Shared_libs...)
 
+	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() {
+				stdlib = stdlib + "_" + ctx.toolchain().RustTriple()
+			}
+
+			// This check is technically insufficient - on the host, where
+			// 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()) {
+				// Dynamically linked stdlib
+				deps.Dylibs = append(deps.Dylibs, stdlib)
+			}
+		}
+	}
 	return deps
 }
 

rust/config/whitelist.go

@@ -5,6 +5,7 @@ var (
 		"external/rust",
 		"external/crosvm",
 		"external/adhd",
+		"prebuilts/rust",
 	}
 
 	RustModuleTypes = []string{

rust/prebuilt.go

@@ -42,6 +42,7 @@ func PrebuiltDylibFactory() android.Module {
 func NewPrebuiltDylib(hod android.HostOrDeviceSupported) (*Module, *prebuiltLibraryDecorator) {
 	module, library := NewRustLibrary(hod)
 	library.BuildOnlyDylib()
+	library.setNoStdlibs()
 	library.setDylib()
 	prebuilt := &prebuiltLibraryDecorator{
 		libraryDecorator: library,

rust/rust_test.go

@@ -209,6 +209,25 @@ func TestProcMacroDeviceDeps(t *testing.T) {
 			name: "libbar",
 			srcs: ["foo.rs"],
 		}
+		// Make a dummy libstd to let resolution go through
+		rust_library_dylib {
+			name: "libstd",
+			crate_name: "std",
+			srcs: ["foo.rs"],
+			no_stdlibs: true,
+		}
+		rust_library_dylib {
+			name: "libterm",
+			crate_name: "term",
+			srcs: ["foo.rs"],
+			no_stdlibs: true,
+		}
+		rust_library_dylib {
+			name: "libtest",
+			crate_name: "test",
+			srcs: ["foo.rs"],
+			no_stdlibs: true,
+		}
 		rust_proc_macro {
 			name: "libpm",
 			rlibs: ["libbar"],
@@ -226,3 +245,18 @@ func TestProcMacroDeviceDeps(t *testing.T) {
 		t.Errorf("Proc_macro is not using host variant of dependent modules.")
 	}
 }
+
+// Test that no_stdlibs suppresses dependencies on rust standard libraries
+func TestNoStdlibs(t *testing.T) {
+	ctx := testRust(t, `
+		rust_binary {
+			name: "fizz-buzz",
+			srcs: ["foo.rs"],
+                        no_stdlibs: true,
+		}`)
+	module := ctx.ModuleForTests("fizz-buzz", "android_arm64_armv8-a_core").Module().(*Module)
+
+	if android.InList("libstd", module.Properties.AndroidMkDylibs) {
+		t.Errorf("no_stdlibs did not suppress dependency on libstd")
+	}
+}