Automatically reorder C/C++ link dependencies in Soong

This uses knowledge of transitive dependencies to reorder
linker command line arguments such that if module A depends
on module B, then module A is automatically listed before
module B in the linker command line.

This should mostly remove the need for Android.bp files to
list all of their static dependencies in link order

Bug: 66260943
Test: reorder the entries of static_libs in an Android.bp and see that linking still succeeds

Change-Id: I20f851ab9f2f30031254e4f30023b6140d15d6c3

cc/cc_test.go

@@ -2,9 +2,12 @@ package cc
 
 import (
 	"android/soong/android"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"reflect"
+	"sort"
+	"strings"
 	"testing"
 
 	"github.com/google/blueprint/proptools"
@@ -43,6 +46,7 @@ func testCc(t *testing.T, bp string) *android.TestContext {
 	ctx.RegisterModuleType("cc_library", android.ModuleFactoryAdaptor(libraryFactory))
 	ctx.RegisterModuleType("toolchain_library", android.ModuleFactoryAdaptor(toolchainLibraryFactory))
 	ctx.RegisterModuleType("llndk_library", android.ModuleFactoryAdaptor(llndkLibraryFactory))
+	ctx.RegisterModuleType("cc_object", android.ModuleFactoryAdaptor(objectFactory))
 	ctx.PreDepsMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.BottomUp("image", vendorMutator).Parallel()
 		ctx.BottomUp("link", linkageMutator).Parallel()
@@ -50,6 +54,64 @@ func testCc(t *testing.T, bp string) *android.TestContext {
 	})
 	ctx.Register()
 
+	// add some modules that are required by the compiler and/or linker
+	bp = bp + `
+		toolchain_library {
+			name: "libatomic",
+			vendor_available: true,
+		}
+
+		toolchain_library {
+			name: "libcompiler_rt-extras",
+			vendor_available: true,
+		}
+
+		toolchain_library {
+			name: "libgcc",
+			vendor_available: true,
+		}
+
+		cc_library {
+			name: "libc",
+			no_libgcc : true,
+			nocrt : true,
+			system_shared_libs: [],
+		}
+		llndk_library {
+			name: "libc",
+			symbol_file: "",
+		}
+		cc_library {
+			name: "libm",
+			no_libgcc : true,
+			nocrt : true,
+			system_shared_libs: [],
+		}
+		llndk_library {
+			name: "libm",
+			symbol_file: "",
+		}
+		cc_library {
+			name: "libdl",
+			no_libgcc : true,
+			nocrt : true,
+			system_shared_libs: [],
+		}
+		llndk_library {
+			name: "libdl",
+			symbol_file: "",
+		}
+
+		cc_object {
+			name: "crtbegin_so",
+		}
+
+		cc_object {
+			name: "crtend_so",
+		}
+
+`
+
 	ctx.MockFileSystem(map[string][]byte{
 		"Android.bp": []byte(bp),
 		"foo.c":      nil,
@@ -57,9 +119,9 @@ func testCc(t *testing.T, bp string) *android.TestContext {
 	})
 
 	_, errs := ctx.ParseBlueprintsFiles("Android.bp")
-	fail(t, errs)
+	failIfErrored(t, errs)
 	_, errs = ctx.PrepareBuildActions(config)
-	fail(t, errs)
+	failIfErrored(t, errs)
 
 	return ctx
 }
@@ -79,44 +141,6 @@ func TestVendorSrc(t *testing.T) {
 				},
 			},
 		}
-		toolchain_library {
-			name: "libatomic",
-			vendor_available: true,
-		}
-		toolchain_library {
-			name: "libcompiler_rt-extras",
-			vendor_available: true,
-		}
-		cc_library {
-			name: "libc",
-			no_libgcc : true,
-			nocrt : true,
-			system_shared_libs: [],
-		}
-		llndk_library {
-			name: "libc",
-			symbol_file: "",
-		}
-		cc_library {
-			name: "libm",
-			no_libgcc : true,
-			nocrt : true,
-			system_shared_libs: [],
-		}
-		llndk_library {
-			name: "libm",
-			symbol_file: "",
-		}
-		cc_library {
-			name: "libdl",
-			no_libgcc : true,
-			nocrt : true,
-			system_shared_libs: [],
-		}
-		llndk_library {
-			name: "libdl",
-			symbol_file: "",
-		}
 	`)
 
 	ld := ctx.ModuleForTests("libTest", "android_arm_armv7-a-neon_vendor_shared").Rule("ld")
@@ -339,3 +363,245 @@ func TestSplitListForSize(t *testing.T) {
 		}
 	}
 }
+
+var staticLinkDepOrderTestCases = []struct {
+	// This is a string representation of a map[moduleName][]moduleDependency .
+	// It models the dependencies declared in an Android.bp file.
+	in string
+
+	// allOrdered is a string representation of a map[moduleName][]moduleDependency .
+	// The keys of allOrdered specify which modules we would like to check.
+	// The values of allOrdered specify the expected result (of the transitive closure of all
+	// dependencies) for each module to test
+	allOrdered string
+
+	// outOrdered is a string representation of a map[moduleName][]moduleDependency .
+	// The keys of outOrdered specify which modules we would like to check.
+	// The values of outOrdered specify the expected result (of the ordered linker command line)
+	// for each module to test.
+	outOrdered string
+}{
+	// Simple tests
+	{
+		in:         "",
+		outOrdered: "",
+	},
+	{
+		in:         "a:",
+		outOrdered: "a:",
+	},
+	{
+		in:         "a:b; b:",
+		outOrdered: "a:b; b:",
+	},
+	// Tests of reordering
+	{
+		// diamond example
+		in:         "a:d,b,c; b:d; c:d; d:",
+		outOrdered: "a:b,c,d; b:d; c:d; d:",
+	},
+	{
+		// somewhat real example
+		in:         "bsdiff_unittest:b,c,d,e,f,g,h,i; e:b",
+		outOrdered: "bsdiff_unittest:c,d,e,b,f,g,h,i; e:b",
+	},
+	{
+		// multiple reorderings
+		in:         "a:b,c,d,e; d:b; e:c",
+		outOrdered: "a:d,b,e,c; d:b; e:c",
+	},
+	{
+		// should reorder without adding new transitive dependencies
+		in:         "bin:lib2,lib1;             lib1:lib2,liboptional",
+		allOrdered: "bin:lib1,lib2,liboptional; lib1:lib2,liboptional",
+		outOrdered: "bin:lib1,lib2;             lib1:lib2,liboptional",
+	},
+	{
+		// multiple levels of dependencies
+		in:         "a:b,c,d,e,f,g,h; f:b,c,d; b:c,d; c:d",
+		allOrdered: "a:e,f,b,c,d,g,h; f:b,c,d; b:c,d; c:d",
+		outOrdered: "a:e,f,b,c,d,g,h; f:b,c,d; b:c,d; c:d",
+	},
+	// tiebreakers for when two modules specifying different orderings and there is no dependency
+	// to dictate an order
+	{
+		// if the tie is between two modules at the end of a's deps, then a's order wins
+		in:         "a1:b,c,d,e; a2:b,c,e,d; b:d,e; c:e,d",
+		outOrdered: "a1:b,c,d,e; a2:b,c,e,d; b:d,e; c:e,d",
+	},
+	{
+		// if the tie is between two modules at the start of a's deps, then c's order is used
+		in:         "a1:d,e,b1,c1; b1:d,e; c1:e,d;   a2:d,e,b2,c2; b2:d,e; c2:d,e",
+		outOrdered: "a1:b1,c1,e,d; b1:d,e; c1:e,d;   a2:b2,c2,d,e; b2:d,e; c2:d,e",
+	},
+	// Tests involving duplicate dependencies
+	{
+		// simple duplicate
+		in:         "a:b,c,c,b",
+		outOrdered: "a:c,b",
+	},
+	{
+		// duplicates with reordering
+		in:         "a:b,c,d,c; c:b",
+		outOrdered: "a:d,c,b",
+	},
+	// Tests to confirm the nonexistence of infinite loops.
+	// These cases should never happen, so as long as the test terminates and the
+	// result is deterministic then that should be fine.
+	{
+		in:         "a:a",
+		outOrdered: "a:a",
+	},
+	{
+		in:         "a:b;   b:c;   c:a",
+		allOrdered: "a:b,c; b:c,a; c:a,b",
+		outOrdered: "a:b;   b:c;   c:a",
+	},
+	{
+		in:         "a:b,c;   b:c,a;   c:a,b",
+		allOrdered: "a:c,a,b; b:a,b,c; c:b,c,a",
+		outOrdered: "a:c,b;   b:a,c;   c:b,a",
+	},
+}
+
+// converts from a string like "a:b,c; d:e" to (["a","b"], {"a":["b","c"], "d":["e"]}, [{"a", "a.o"}, {"b", "b.o"}])
+func parseModuleDeps(text string) (modulesInOrder []android.Path, allDeps map[android.Path][]android.Path) {
+	// convert from "a:b,c; d:e" to "a:b,c;d:e"
+	strippedText := strings.Replace(text, " ", "", -1)
+	if len(strippedText) < 1 {
+		return []android.Path{}, make(map[android.Path][]android.Path, 0)
+	}
+	allDeps = make(map[android.Path][]android.Path, 0)
+
+	// convert from "a:b,c;d:e" to ["a:b,c", "d:e"]
+	moduleTexts := strings.Split(strippedText, ";")
+
+	outputForModuleName := func(moduleName string) android.Path {
+		return android.PathForTesting(moduleName)
+	}
+
+	for _, moduleText := range moduleTexts {
+		// convert from "a:b,c" to ["a", "b,c"]
+		components := strings.Split(moduleText, ":")
+		if len(components) != 2 {
+			panic(fmt.Sprintf("illegal module dep string %q from larger string %q; must contain one ':', not %v", moduleText, text, len(components)-1))
+		}
+		moduleName := components[0]
+		moduleOutput := outputForModuleName(moduleName)
+		modulesInOrder = append(modulesInOrder, moduleOutput)
+
+		depString := components[1]
+		// convert from "b,c" to ["b", "c"]
+		depNames := strings.Split(depString, ",")
+		if len(depString) < 1 {
+			depNames = []string{}
+		}
+		var deps []android.Path
+		for _, depName := range depNames {
+			deps = append(deps, outputForModuleName(depName))
+		}
+		allDeps[moduleOutput] = deps
+	}
+	return modulesInOrder, allDeps
+}
+
+func TestStaticLinkDependencyOrdering(t *testing.T) {
+	for _, testCase := range staticLinkDepOrderTestCases {
+		errs := []string{}
+
+		// parse testcase
+		_, givenTransitiveDeps := parseModuleDeps(testCase.in)
+		expectedModuleNames, expectedTransitiveDeps := parseModuleDeps(testCase.outOrdered)
+		if testCase.allOrdered == "" {
+			// allow the test case to skip specifying allOrdered
+			testCase.allOrdered = testCase.outOrdered
+		}
+		_, expectedAllDeps := parseModuleDeps(testCase.allOrdered)
+
+		// For each module whose post-reordered dependencies were specified, validate that
+		// reordering the inputs produces the expected outputs.
+		for _, moduleName := range expectedModuleNames {
+			moduleDeps := givenTransitiveDeps[moduleName]
+			orderedAllDeps, orderedDeclaredDeps := orderDeps(moduleDeps, givenTransitiveDeps)
+
+			correctAllOrdered := expectedAllDeps[moduleName]
+			if !reflect.DeepEqual(orderedAllDeps, correctAllOrdered) {
+				errs = append(errs, fmt.Sprintf("orderDeps returned incorrect orderedAllDeps."+
+					"\nInput:    %q"+
+					"\nmodule:   %v"+
+					"\nexpected: %s"+
+					"\nactual:   %s",
+					testCase.in, moduleName, correctAllOrdered, orderedAllDeps))
+			}
+
+			correctOutputDeps := expectedTransitiveDeps[moduleName]
+			if !reflect.DeepEqual(correctOutputDeps, orderedDeclaredDeps) {
+				errs = append(errs, fmt.Sprintf("orderDeps returned incorrect orderedDeclaredDeps."+
+					"\nInput:    %q"+
+					"\nmodule:   %v"+
+					"\nexpected: %s"+
+					"\nactual:   %s",
+					testCase.in, moduleName, correctOutputDeps, orderedDeclaredDeps))
+			}
+		}
+
+		if len(errs) > 0 {
+			sort.Strings(errs)
+			for _, err := range errs {
+				t.Error(err)
+			}
+		}
+	}
+}
+func failIfErrored(t *testing.T, errs []error) {
+	if len(errs) > 0 {
+		for _, err := range errs {
+			t.Error(err)
+		}
+		t.FailNow()
+	}
+}
+
+func getOutputPaths(ctx *android.TestContext, variant string, moduleNames []string) (paths android.Paths) {
+	for _, moduleName := range moduleNames {
+		module := ctx.ModuleForTests(moduleName, variant).Module().(*Module)
+		output := module.outputFile.Path()
+		paths = append(paths, output)
+	}
+	return paths
+}
+
+func TestLibDeps(t *testing.T) {
+	ctx := testCc(t, `
+	cc_library {
+		name: "a",
+		static_libs: ["b", "c", "d"],
+	}
+	cc_library {
+		name: "b",
+	}
+	cc_library {
+		name: "c",
+		static_libs: ["b"],
+	}
+	cc_library {
+		name: "d",
+	}
+
+	`)
+
+	variant := "android_arm64_armv8-a_core_static"
+	moduleA := ctx.ModuleForTests("a", variant).Module().(*Module)
+	actual := moduleA.staticDepsInLinkOrder
+	expected := getOutputPaths(ctx, variant, []string{"c", "b", "d"})
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("staticDeps orderings were not propagated correctly"+
+			"\nactual:   %v"+
+			"\nexpected: %v",
+			actual,
+			expected,
+		)
+	}
+
+}