compiler, reflect: replace package and name length with null-byte termination

compiler/interface.go

@@ -112,10 +112,8 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 			typeFieldTypes = append(typeFieldTypes,
 				types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
 				types.NewVar(token.NoPos, nil, "underlying", types.Typ[types.UnsafePointer]),
-				types.NewVar(token.NoPos, nil, "pkglen", types.Typ[types.Uintptr]),
 				types.NewVar(token.NoPos, nil, "pkgpath", types.Typ[types.UnsafePointer]),
-				types.NewVar(token.NoPos, nil, "len", types.Typ[types.Uintptr]),
-				types.NewVar(token.NoPos, nil, "name", types.NewArray(types.Typ[types.Int8], int64(len(typ.Obj().Name())))),
+				types.NewVar(token.NoPos, nil, "name", types.NewArray(types.Typ[types.Int8], 1+int64(len(typ.Obj().Name())))),
 			)
 		case *types.Chan, *types.Slice:
 			typeFieldTypes = append(typeFieldTypes,
@@ -183,7 +181,7 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 				pkgpathName = "reflect/types.type.pkgpath:" + pkgpath
 			}
 
-			pkgpathInitializer := c.ctx.ConstString(pkgpath, false)
+			pkgpathInitializer := c.ctx.ConstString(pkgpath+"\x00", false)
 			pkgpathGlobal := llvm.AddGlobal(c.mod, pkgpathInitializer.Type(), pkgpathName)
 			pkgpathGlobal.SetInitializer(pkgpathInitializer)
 			pkgpathGlobal.SetAlignment(1)
@@ -196,12 +194,10 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 			})
 
 			typeFields = []llvm.Value{
-				c.getTypeCode(types.NewPointer(typ)),                      // ptrTo
-				c.getTypeCode(typ.Underlying()),                           // underlying
-				llvm.ConstInt(c.uintptrType, uint64(len(pkgpath)), false), // pkgpath length
-				pkgpathPtr, // pkgpath pointer
-				llvm.ConstInt(c.uintptrType, uint64(len(name)), false), // length
-				c.ctx.ConstString(name, false),                         // name
+				c.getTypeCode(types.NewPointer(typ)),  // ptrTo
+				c.getTypeCode(typ.Underlying()),       // underlying
+				pkgpathPtr,                            // pkgpath pointer
+				c.ctx.ConstString(name+"\x00", false), // name
 			}
 			metabyte |= 1 << 5 // "named" flag
 		case *types.Chan:

compiler/testdata/interface.ll

@@ -9,8 +9,8 @@ target triple = "wasm32-unknown-wasi"
 @"reflect/types.type:basic:int" = linkonce_odr constant { i8, ptr } { i8 2, ptr @"reflect/types.type:pointer:basic:int" }, align 4
 @"reflect/types.type:pointer:basic:int" = linkonce_odr constant { i8, ptr } { i8 21, ptr @"reflect/types.type:basic:int" }, align 4
 @"reflect/types.type:pointer:named:error" = linkonce_odr constant { i8, ptr } { i8 21, ptr @"reflect/types.type:named:error" }, align 4
-@"reflect/types.type:named:error" = linkonce_odr constant { i8, ptr, ptr, i32, ptr, i32, [5 x i8] } { i8 52, ptr @"reflect/types.type:pointer:named:error", ptr @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, ptr @"reflect/types.type.pkgpath.empty", i32 5, [5 x i8] c"error" }, align 4
-@"reflect/types.type.pkgpath.empty" = linkonce_odr unnamed_addr constant [0 x i8] zeroinitializer, align 1
+@"reflect/types.type:named:error" = linkonce_odr constant { i8, ptr, ptr, ptr, [6 x i8] } { i8 52, ptr @"reflect/types.type:pointer:named:error", ptr @"reflect/types.type:interface:{Error:func:{}{basic:string}}", ptr @"reflect/types.type.pkgpath.empty", [6 x i8] c"error\00" }, align 4
+@"reflect/types.type.pkgpath.empty" = linkonce_odr unnamed_addr constant [1 x i8] zeroinitializer, align 1
 @"reflect/types.type:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant { i8, ptr } { i8 20, ptr @"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" }, align 4
 @"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant { i8, ptr } { i8 21, ptr @"reflect/types.type:interface:{Error:func:{}{basic:string}}" }, align 4
 @"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" = linkonce_odr constant { i8, ptr } { i8 21, ptr @"reflect/types.type:interface:{String:func:{}{basic:string}}" }, align 4

src/reflect/type.go

@@ -50,9 +50,7 @@
 //     meta         uint8
 //     ptrTo        *typeStruct
 //     elem         *typeStruct // underlying type
-//     plen         uintptr     // length of pkgpath
 //     pkg          *byte       // pkgpath
-//     nlem         uintptr     // length of name
 //     name         [1]byte     // actual name; length nlem
 //
 // The type struct is essentially a union of all the above types. Which it is,
@@ -430,9 +428,7 @@ type namedType struct {
 	rawType
 	ptrTo *rawType
 	elem  *rawType
-	plen  uintptr
 	pkg   *byte
-	nlen  uintptr
 	name  [1]byte
 }
 
@@ -896,10 +892,25 @@ func (t *rawType) NumMethod() int {
 	panic("unimplemented: (reflect.Type).NumMethod()")
 }
 
+// Read and return a null terminated string starting from data.
+func readStringZ(data unsafe.Pointer) string {
+	start := data
+	var len uintptr
+	for *(*byte)(data) != 0 {
+		len++
+		data = unsafe.Add(data, 1) // C: data++
+	}
+
+	return *(*string)(unsafe.Pointer(&stringHeader{
+		data: start,
+		len:  len,
+	}))
+}
+
 func (t *rawType) Name() string {
 	if t.isNamed() {
 		ntype := (*namedType)(unsafe.Pointer(t))
-		return unsafe.String(&ntype.name[0], ntype.nlen)
+		return readStringZ(unsafe.Pointer(&ntype.name[0]))
 	}
 
 	return t.Kind().String()
@@ -924,7 +935,7 @@ func (t rawType) MethodByName(name string) (Method, bool) {
 func (t *rawType) PkgPath() string {
 	if t.isNamed() {
 		ntype := (*namedType)(unsafe.Pointer(t))
-		return unsafe.String(ntype.pkg, ntype.plen)
+		return readStringZ(unsafe.Pointer(ntype.pkg))
 	}
 
 	return ""