diff --git a/src/os/env.go b/src/os/env.go
new file mode 100644
index 00000000..3a250df0
--- /dev/null
+++ b/src/os/env.go
@@ -0,0 +1,5 @@
+package os
+
+func Getenv(key string) string {
+	return ""
+}
diff --git a/src/os/errors.go b/src/os/errors.go
new file mode 100644
index 00000000..9b346554
--- /dev/null
+++ b/src/os/errors.go
@@ -0,0 +1,39 @@
+package os
+
+import (
+	"errors"
+)
+
+var (
+	ErrInvalid    = errors.New("invalid argument")
+	ErrPermission = errors.New("permission denied")
+	ErrClosed     = errors.New("file already closed")
+
+	// Portable analogs of some common system call errors.
+	// Note that these are exported for use in the Filesystem interface.
+	ErrUnsupported    = errors.New("operation not supported")
+	ErrNotImplemented = errors.New("operation not implemented")
+	ErrNotExist       = errors.New("file not found")
+	ErrExist          = errors.New("file exists")
+)
+
+func IsPermission(err error) bool {
+	return err == ErrPermission
+}
+
+func NewSyscallError(syscall string, err error) error {
+	if err == nil {
+		return nil
+	}
+	return &SyscallError{syscall, err}
+}
+
+// SyscallError records an error from a specific system call.
+type SyscallError struct {
+	Syscall string
+	Err     error
+}
+
+func (e *SyscallError) Error() string { return e.Syscall + ": " + e.Err.Error() }
+
+func (e *SyscallError) Unwrap() error { return e.Err }
diff --git a/src/os/exec.go b/src/os/exec.go
new file mode 100644
index 00000000..66cc7999
--- /dev/null
+++ b/src/os/exec.go
@@ -0,0 +1,6 @@
+package os
+
+type Signal interface {
+	String() string
+	Signal() // to distinguish from other Stringers
+}
diff --git a/src/os/file.go b/src/os/file.go
index 6f4a8cc1..a059a421 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -6,16 +6,7 @@
 package os
 
 import (
-	"errors"
-)
-
-// Portable analogs of some common system call errors.
-// Note that these are exported for use in the Filesystem interface.
-var (
-	ErrUnsupported    = errors.New("operation not supported")
-	ErrNotImplemented = errors.New("operation not implemented")
-	ErrNotExist       = errors.New("file not found")
-	ErrExist          = errors.New("file exists")
+	"syscall"
 )
 
 // Mkdir creates a directory. If the operation fails, it will return an error of
@@ -91,6 +82,10 @@ func (f *File) Read(b []byte) (n int, err error) {
 	return
 }
 
+func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
+	return 0, ErrNotImplemented
+}
+
 // Write writes len(b) bytes to the File. It returns the number of bytes written
 // and an error, if any. Write returns a non-nil error when n != len(b).
 func (f *File) Write(b []byte) (n int, err error) {
@@ -125,6 +120,20 @@ func (f *File) Stat() (FileInfo, error) {
 	return nil, &PathError{"stat", f.name, ErrNotImplemented}
 }
 
+// Sync is a stub, not yet implemented
+func (f *File) Sync() error {
+	return ErrNotImplemented
+}
+
+func (f *File) SyscallConn() (syscall.RawConn, error) {
+	return nil, ErrNotImplemented
+}
+
+// Fd returns the file handle referencing the open file.
+func (f *File) Fd() uintptr {
+	panic("unimplemented: os.file.Fd()")
+}
+
 const (
 	PathSeparator     = '/' // OS-specific path separator
 	PathListSeparator = ':' // OS-specific path list separator
@@ -194,7 +203,7 @@ type FileInfo interface {
 	Name() string   // base name of the file
 	Size() int64    // length in bytes for regular files; system-dependent for others
 	Mode() FileMode // file mode bits
-	// ModTime() time.Time // modification time
+	// TODO ModTime() time.Time // modification time
 	IsDir() bool      // abbreviation for Mode().IsDir()
 	Sys() interface{} // underlying data source (can return nil)
 }
diff --git a/src/os/sys.go b/src/os/sys.go
new file mode 100644
index 00000000..ba300e40
--- /dev/null
+++ b/src/os/sys.go
@@ -0,0 +1,5 @@
+package os
+
+func Hostname() (name string, err error) {
+	return "", ErrNotImplemented
+}
diff --git a/src/reflect/deepequal.go b/src/reflect/deepequal.go
new file mode 100644
index 00000000..32719c34
--- /dev/null
+++ b/src/reflect/deepequal.go
@@ -0,0 +1,9 @@
+package reflect
+
+func DeepEqual(x, y interface{}) bool {
+	if x == nil || y == nil {
+		return x == y
+	}
+
+	panic("unimplemented: reflect.DeepEqual()")
+}
diff --git a/src/reflect/strconv.go b/src/reflect/strconv.go
new file mode 100644
index 00000000..9b07cb45
--- /dev/null
+++ b/src/reflect/strconv.go
@@ -0,0 +1,248 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package reflect
+
+import (
+	"unicode/utf8"
+)
+
+// errSyntax indicates that a value does not have the right syntax for the target type.
+var errSyntax = badSyntax{}
+
+type badSyntax struct{}
+
+func (badSyntax) Error() string {
+	return "invalid syntax"
+}
+
+func unhex(b byte) (v rune, ok bool) {
+	c := rune(b)
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0', true
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10, true
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10, true
+	}
+	return
+}
+
+// unquoteChar decodes the first character or byte in the escaped string
+// or character literal represented by the string s.
+// It returns four values:
+//
+//	1) value, the decoded Unicode code point or byte value;
+//	2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
+//	3) tail, the remainder of the string after the character; and
+//	4) an error that will be nil if the character is syntactically valid.
+//
+// The second argument, quote, specifies the type of literal being parsed
+// and therefore which escaped quote character is permitted.
+// If set to a single quote, it permits the sequence \' and disallows unescaped '.
+// If set to a double quote, it permits \" and disallows unescaped ".
+// If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
+func unquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
+	// easy cases
+	if len(s) == 0 {
+		err = errSyntax
+		return
+	}
+	switch c := s[0]; {
+	case c == quote && (quote == '\'' || quote == '"'):
+		err = errSyntax
+		return
+	case c >= utf8.RuneSelf:
+		r, size := utf8.DecodeRuneInString(s)
+		return r, true, s[size:], nil
+	case c != '\\':
+		return rune(s[0]), false, s[1:], nil
+	}
+
+	// hard case: c is backslash
+	if len(s) <= 1 {
+		err = errSyntax
+		return
+	}
+	c := s[1]
+	s = s[2:]
+
+	switch c {
+	case 'a':
+		value = '\a'
+	case 'b':
+		value = '\b'
+	case 'f':
+		value = '\f'
+	case 'n':
+		value = '\n'
+	case 'r':
+		value = '\r'
+	case 't':
+		value = '\t'
+	case 'v':
+		value = '\v'
+	case 'x', 'u', 'U':
+		n := 0
+		switch c {
+		case 'x':
+			n = 2
+		case 'u':
+			n = 4
+		case 'U':
+			n = 8
+		}
+		var v rune
+		if len(s) < n {
+			err = errSyntax
+			return
+		}
+		for j := 0; j < n; j++ {
+			x, ok := unhex(s[j])
+			if !ok {
+				err = errSyntax
+				return
+			}
+			v = v<<4 | x
+		}
+		s = s[n:]
+		if c == 'x' {
+			// single-byte string, possibly not UTF-8
+			value = v
+			break
+		}
+		if v > utf8.MaxRune {
+			err = errSyntax
+			return
+		}
+		value = v
+		multibyte = true
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		v := rune(c) - '0'
+		if len(s) < 2 {
+			err = errSyntax
+			return
+		}
+		for j := 0; j < 2; j++ { // one digit already; two more
+			x := rune(s[j]) - '0'
+			if x < 0 || x > 7 {
+				err = errSyntax
+				return
+			}
+			v = (v << 3) | x
+		}
+		s = s[2:]
+		if v > 255 {
+			err = errSyntax
+			return
+		}
+		value = v
+	case '\\':
+		value = '\\'
+	case '\'', '"':
+		if c != quote {
+			err = errSyntax
+			return
+		}
+		value = rune(c)
+	default:
+		err = errSyntax
+		return
+	}
+	tail = s
+	return
+}
+
+// unquote interprets s as a single-quoted, double-quoted,
+// or backquoted Go string literal, returning the string value
+// that s quotes.  (If s is single-quoted, it would be a Go
+// character literal; unquote returns the corresponding
+// one-character string.)
+func unquote(s string) (string, error) {
+	n := len(s)
+	if n < 2 {
+		return "", errSyntax
+	}
+	quote := s[0]
+	if quote != s[n-1] {
+		return "", errSyntax
+	}
+	s = s[1 : n-1]
+
+	if quote == '`' {
+		if contains(s, '`') {
+			return "", errSyntax
+		}
+		if contains(s, '\r') {
+			// -1 because we know there is at least one \r to remove.
+			buf := make([]byte, 0, len(s)-1)
+			for i := 0; i < len(s); i++ {
+				if s[i] != '\r' {
+					buf = append(buf, s[i])
+				}
+			}
+			return string(buf), nil
+		}
+		return s, nil
+	}
+	if quote != '"' && quote != '\'' {
+		return "", errSyntax
+	}
+	if contains(s, '\n') {
+		return "", errSyntax
+	}
+
+	// Is it trivial? Avoid allocation.
+	if !contains(s, '\\') && !contains(s, quote) {
+		switch quote {
+		case '"':
+			if utf8.ValidString(s) {
+				return s, nil
+			}
+		case '\'':
+			r, size := utf8.DecodeRuneInString(s)
+			if size == len(s) && (r != utf8.RuneError || size != 1) {
+				return s, nil
+			}
+		}
+	}
+
+	var runeTmp [utf8.UTFMax]byte
+	buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
+	for len(s) > 0 {
+		c, multibyte, ss, err := unquoteChar(s, quote)
+		if err != nil {
+			return "", err
+		}
+		s = ss
+		if c < utf8.RuneSelf || !multibyte {
+			buf = append(buf, byte(c))
+		} else {
+			n := utf8.EncodeRune(runeTmp[:], c)
+			buf = append(buf, runeTmp[:n]...)
+		}
+		if quote == '\'' && len(s) != 0 {
+			// single-quoted must be single character
+			return "", errSyntax
+		}
+	}
+	return string(buf), nil
+}
+
+// contains reports whether the string contains the byte c.
+func contains(s string, c byte) bool {
+	return indexByteString(s, c) != -1
+}
+
+// Index finds the index of the first instance of the specified byte in the string.
+// If the byte is not found, this returns -1.
+func indexByteString(s string, c byte) int {
+	for i := 0; i < len(s); i++ {
+		if s[i] == c {
+			return i
+		}
+	}
+	return -1
+}
diff --git a/src/reflect/type.go b/src/reflect/type.go
index 44dc10cb..237a5a6a 100644
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -1,3 +1,7 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package reflect
 
 import (
@@ -227,7 +231,7 @@ func (t Type) Field(i int) StructField {
 			// There is a tag.
 			var tagNum uintptr
 			tagNum, p = readVarint(p)
-			field.Tag = readStringSidetable(unsafe.Pointer(&structNamesSidetable), tagNum)
+			field.Tag = StructTag(readStringSidetable(unsafe.Pointer(&structNamesSidetable), tagNum))
 		} else {
 			// There is no tag.
 			field.Tag = ""
@@ -445,6 +449,22 @@ func (t Type) Comparable() bool {
 	}
 }
 
+func (t Type) ConvertibleTo(u Type) bool {
+	panic("unimplemented: (reflect.Type).ConvertibleTo()")
+}
+
+func (t Type) NumMethod() int {
+	panic("unimplemented: (reflect.Type).NumMethod()")
+}
+
+func (t Type) Name() string {
+	panic("unimplemented: (reflect.Type).Name()")
+}
+
+func (t Type) Key() Type {
+	panic("unimplemented: (reflect.Type).Key()")
+}
+
 // A StructField describes a single field in a struct.
 type StructField struct {
 	// Name indicates the field name.
@@ -455,11 +475,75 @@ type StructField struct {
 	PkgPath string
 
 	Type      Type
-	Tag       string
+	Tag       StructTag // field tag string
 	Anonymous bool
 	Offset    uintptr
 }
 
+// A StructTag is the tag string in a struct field.
+type StructTag string
+
+// TODO: it would be feasible to do the key/value splitting at compile time,
+// avoiding the code size cost of doing it at runtime
+
+// Get returns the value associated with key in the tag string.
+func (tag StructTag) Get(key string) string {
+	v, _ := tag.Lookup(key)
+	return v
+}
+
+// Lookup returns the value associated with key in the tag string.
+func (tag StructTag) Lookup(key string) (value string, ok bool) {
+	for tag != "" {
+		// Skip leading space.
+		i := 0
+		for i < len(tag) && tag[i] == ' ' {
+			i++
+		}
+		tag = tag[i:]
+		if tag == "" {
+			break
+		}
+
+		// Scan to colon. A space, a quote or a control character is a syntax error.
+		// Strictly speaking, control chars include the range [0x7f, 0x9f], not just
+		// [0x00, 0x1f], but in practice, we ignore the multi-byte control characters
+		// as it is simpler to inspect the tag's bytes than the tag's runes.
+		i = 0
+		for i < len(tag) && tag[i] > ' ' && tag[i] != ':' && tag[i] != '"' && tag[i] != 0x7f {
+			i++
+		}
+		if i == 0 || i+1 >= len(tag) || tag[i] != ':' || tag[i+1] != '"' {
+			break
+		}
+		name := string(tag[:i])
+		tag = tag[i+1:]
+
+		// Scan quoted string to find value.
+		i = 1
+		for i < len(tag) && tag[i] != '"' {
+			if tag[i] == '\\' {
+				i++
+			}
+			i++
+		}
+		if i >= len(tag) {
+			break
+		}
+		qvalue := string(tag[:i+1])
+		tag = tag[i+1:]
+
+		if key == name {
+			value, err := unquote(qvalue)
+			if err != nil {
+				break
+			}
+			return value, true
+		}
+	}
+	return "", false
+}
+
 // TypeError is the error that is used in a panic when invoking a method on a
 // type that is not applicable to that type.
 type TypeError struct {
diff --git a/src/reflect/value.go b/src/reflect/value.go
index e71eaee8..087ddfa1 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -661,6 +661,18 @@ func (v Value) checkAddressable() {
 	}
 }
 
+func (v Value) OverflowInt(x int64) bool {
+	panic("unimplemented: reflect.OverflowInt()")
+}
+
+func (v Value) OverflowUint(x uint64) bool {
+	panic("unimplemented: reflect.OverflowUint()")
+}
+
+func (v Value) Convert(t Type) Value {
+	panic("unimplemented: (reflect.Value).Convert()")
+}
+
 func MakeSlice(typ Type, len, cap int) Value {
 	panic("unimplemented: reflect.MakeSlice()")
 }
@@ -700,3 +712,33 @@ func (e *ValueError) Error() string {
 // Calls to this function are converted to LLVM intrinsic calls such as
 // llvm.memcpy.p0i8.p0i8.i32().
 func memcpy(dst, src unsafe.Pointer, size uintptr)
+
+// Copy copies the contents of src into dst until either
+// dst has been filled or src has been exhausted.
+func Copy(dst, src Value) int {
+	panic("unimplemented: reflect.Copy()")
+}
+
+// Append appends the values x to a slice s and returns the resulting slice.
+// As in Go, each x's value must be assignable to the slice's element type.
+func Append(s Value, x ...Value) Value {
+	panic("unimplemented: reflect.Append()")
+}
+
+func (v Value) SetMapIndex(key, elem Value) {
+	panic("unimplemented: (reflect.Value).SetMapIndex()")
+}
+
+// FieldByIndex returns the nested field corresponding to index.
+func (v Value) FieldByIndex(index []int) Value {
+	panic("unimplemented: (reflect.Value).FieldByIndex()")
+}
+
+func (v Value) FieldByName(name string) Value {
+	panic("unimplemented: (reflect.Value).FieldByName()")
+}
+
+// MakeMap creates a new map with the specified type.
+func MakeMap(typ Type) Value {
+	panic("unimplemented: reflect.MakeMap()")
+}
diff --git a/src/runtime/error.go b/src/runtime/error.go
new file mode 100644
index 00000000..3ae5ea3a
--- /dev/null
+++ b/src/runtime/error.go
@@ -0,0 +1,8 @@
+package runtime
+
+// The Error interface identifies a run time error.
+type Error interface {
+	error
+
+	RuntimeError()
+}
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index c2cff3d0..5ef9b7ad 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -14,3 +14,7 @@ func (f *Func) Name() string {
 func Caller(skip int) (pc uintptr, file string, line int, ok bool) {
 	return 0, "", 0, false
 }
+
+func Stack(buf []byte, all bool) int {
+	return 0
+}
diff --git a/src/sync/map.go b/src/sync/map.go
index 7d3cde8a..5eeff9d3 100644
--- a/src/sync/map.go
+++ b/src/sync/map.go
@@ -42,3 +42,18 @@ func (m *Map) Store(key, value interface{}) {
 	}
 	m.m[key] = value
 }
+
+func (m *Map) Range(f func(key, value interface{}) bool) {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.m == nil {
+		return
+	}
+
+	for k, v := range m.m {
+		if !f(k, v) {
+			break
+		}
+	}
+}
diff --git a/src/sync/mutex.go b/src/sync/mutex.go
index acc02de3..7284300f 100644
--- a/src/sync/mutex.go
+++ b/src/sync/mutex.go
@@ -74,3 +74,14 @@ type Locker interface {
 	Lock()
 	Unlock()
 }
+
+// RLocker returns a Locker interface that implements
+// the Lock and Unlock methods by calling rw.RLock and rw.RUnlock.
+func (rw *RWMutex) RLocker() Locker {
+	return (*rlocker)(rw)
+}
+
+type rlocker RWMutex
+
+func (r *rlocker) Lock()   { (*RWMutex)(r).RLock() }
+func (r *rlocker) Unlock() { (*RWMutex)(r).RUnlock() }
diff --git a/src/syscall/net.go b/src/syscall/net.go
new file mode 100644
index 00000000..531fa80d
--- /dev/null
+++ b/src/syscall/net.go
@@ -0,0 +1,34 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package syscall
+
+// A RawConn is a raw network connection.
+type RawConn interface {
+	// Control invokes f on the underlying connection's file
+	// descriptor or handle.
+	// The file descriptor fd is guaranteed to remain valid while
+	// f executes but not after f returns.
+	Control(f func(fd uintptr)) error
+
+	// Read invokes f on the underlying connection's file
+	// descriptor or handle; f is expected to try to read from the
+	// file descriptor.
+	// If f returns true, Read returns. Otherwise Read blocks
+	// waiting for the connection to be ready for reading and
+	// tries again repeatedly.
+	// The file descriptor is guaranteed to remain valid while f
+	// executes but not after f returns.
+	Read(f func(fd uintptr) (done bool)) error
+
+	// Write is like Read but for writing.
+	Write(f func(fd uintptr) (done bool)) error
+}
+
+// Conn is implemented by some types in the net and os packages to provide
+// access to the underlying file descriptor or handle.
+type Conn interface {
+	// SyscallConn returns a raw network connection.
+	SyscallConn() (RawConn, error)
+}
diff --git a/testdata/reflect.go b/testdata/reflect.go
index 40b1969c..c4df8460 100644
--- a/testdata/reflect.go
+++ b/testdata/reflect.go
@@ -264,6 +264,9 @@ func main() {
 	default:
 		println("type assertion failed (but should succeed)")
 	}
+
+	println("\nstruct tags")
+	TestStructTag()
 }
 
 func emptyFunc() {
@@ -352,3 +355,14 @@ func assertSize(ok bool, typ string) {
 }
 
 type unreferencedType int
+
+func TestStructTag() {
+	type S struct {
+		F string `species:"gopher" color:"blue"`
+	}
+
+	s := S{}
+	st := reflect.TypeOf(s)
+	field := st.Field(0)
+	println(field.Tag.Get("color"), field.Tag.Get("species"))
+}
diff --git a/testdata/reflect.txt b/testdata/reflect.txt
index 28361306..eeaa9c6f 100644
--- a/testdata/reflect.txt
+++ b/testdata/reflect.txt
@@ -336,3 +336,6 @@ float64 8 64
 complex64 8 64
 complex128 16 128
 type assertion succeeded for unreferenced type
+
+struct tags
+blue gopher