Ensure the marshalled object doesn't escape.

Add new Marshallable interface methods CopyIn/CopyOut, which can be directly
called on the marshalled object, avoiding an interface indirection. Such
indirections are problematic because they always cause the marshalled object to
escape.

PiperOrigin-RevId: 295028010

1 files changed, 24 insertions, 15 deletions

diff --git a/tools/go_marshal/gomarshal/generator.go b/tools/go_marshal/gomarshal/generator.go
index 0b3f600fe..01be7c477 100644
--- a/tools/go_marshal/gomarshal/generator.go
+++ b/tools/go_marshal/gomarshal/generator.go
@@ -34,9 +34,9 @@ const (
 	usermemImport  = "gvisor.dev/gvisor/pkg/usermem"
 )
 
-// List of identifiers we use in generated code, that may conflict a
-// similarly-named source identifier. Avoid problems by refusing the generate
-// code when we see these.
+// List of identifiers we use in generated code that may conflict with a
+// similarly-named source identifier. Abort gracefully when we see these to
+// avoid potentially confusing compilation failures in generated code.
 //
 // This only applies to import aliases at the moment. All other identifiers
 // are qualified by a receiver argument, since they're struct fields.
@@ -44,10 +44,20 @@ const (
 // All recievers are single letters, so we don't allow import aliases to be a
 // single letter.
 var badIdents = []string{
-	"src", "srcs", "dst", "dsts", "blk", "buf", "err",
+	"addr", "blk", "buf", "dst", "dsts", "err", "hdr", "len", "ptr", "src", "srcs", "task", "val",
 	// All single-letter identifiers.
 }
 
+// Constructed fromt badIdents in init().
+var badIdentsMap map[string]struct{}
+
+func init() {
+	badIdentsMap = make(map[string]struct{})
+	for _, ident := range badIdents {
+		badIdentsMap[ident] = struct{}{}
+	}
+}
+
 // Generator drives code generation for a single invocation of the go_marshal
 // utility.
 //
@@ -88,16 +98,18 @@ func NewGenerator(srcs []string, out, outTest, pkg string, imports []string) (*G
 	}
 	for _, i := range imports {
 		// All imports on the extra imports list are unconditionally marked as
-		// used, so they're always added to the generated code.
+		// used, so that they're always added to the generated code.
 		g.imports.add(i).markUsed()
 	}
 	g.imports.add(marshalImport).markUsed()
-	// The follow imports may or may not be used by the generated
-	// code, depending what's required for the target types. Don't
-	// mark these imports as used by default.
-	g.imports.add(usermemImport)
+	// The following imports may or may not be used by the generated code,
+	// depending on what's required for the target types. Don't mark these as
+	// used by default.
+	g.imports.add("reflect")
+	g.imports.add("runtime")
 	g.imports.add(safecopyImport)
 	g.imports.add("unsafe")
+	g.imports.add(usermemImport)
 
 	return &g, nil
 }
@@ -229,11 +241,6 @@ func (g *Generator) collectMarshallabeTypes(a *ast.File, f *token.FileSet) []*as
 // identifiers in the generated code don't conflict with any imported package
 // names.
 func (g *Generator) collectImports(a *ast.File, f *token.FileSet) map[string]importStmt {
-	badImportNames := make(map[string]bool)
-	for _, i := range badIdents {
-		badImportNames[i] = true
-	}
-
 	is := make(map[string]importStmt)
 	for _, decl := range a.Decls {
 		gdecl, ok := decl.(*ast.GenDecl)
@@ -250,7 +257,7 @@ func (g *Generator) collectImports(a *ast.File, f *token.FileSet) map[string]imp
 			if len(i.name) == 1 {
 				abortAt(f.Position(spec.Pos()), fmt.Sprintf("Import has a single character local name '%s'; this may conflict with code generated by go_marshal, use a multi-character import alias", i.name))
 			}
-			if badImportNames[i.name] {
+			if _, ok := badIdentsMap[i.name]; ok {
 				abortAt(f.Position(spec.Pos()), fmt.Sprintf("Import name '%s' is likely to conflict with code generated by go_marshal, use a different import alias", i.name))
 			}
 		}
@@ -371,6 +378,7 @@ func (g *Generator) writeTests(ts []*testGenerator) error {
 		return err
 	}
 
+	// Collect and write test import statements.
 	imports := newImportTable()
 	for _, t := range ts {
 		imports.merge(t.imports)
@@ -380,6 +388,7 @@ func (g *Generator) writeTests(ts []*testGenerator) error {
 		return err
 	}
 
+	// Write test functions.
 	for _, t := range ts {
 		if err := t.write(g.outputTest); err != nil {
 			return err