// 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.
// Runtime type representation.
package runtime
import "unsafe"
// tflag is documented in reflect/type.go.
//
// tflag values must be kept in sync with copies in:
// cmd/compile/internal/gc/reflect.go
// cmd/link/internal/ld/decodesym.go
// reflect/type.go
type tflag uint8
const (
tflagUncommon tflag = 1 << 0
tflagExtraStar tflag = 1 << 1
tflagNamed tflag = 1 << 2
)
// Needs to be in sync with ../cmd/link/internal/ld/decodesym.go:/^func.commonsize,
// ../cmd/compile/internal/gc/reflect.go:/^func.dcommontype and
// ../reflect/type.go:/^type.rtype.
type _type struct {
size uintptr
ptrdata uintptr // size of memory prefix holding all pointers
hash uint32
tflag tflag
align uint8
fieldalign uint8
kind uint8
alg *typeAlg
// gcdata stores the GC type data for the garbage collector.
// If the KindGCProg bit is set in kind, gcdata is a GC program.
// Otherwise it is a ptrmask bitmap. See mbitmap.go for details.
gcdata *byte
str nameOff
ptrToThis typeOff
}
func (t *_type) string() string {
s := t.nameOff(t.str).name()
if t.tflag&tflagExtraStar != 0 {
return s[1:]
}
return s
}
func (t *_type) uncommon() *uncommontype {
if t.tflag&tflagUncommon == 0 {
return nil
}
switch t.kind & kindMask {
case kindStruct:
type u struct {
structtype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindPtr:
type u struct {
ptrtype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindFunc:
type u struct {
functype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindSlice:
type u struct {
slicetype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindArray:
type u struct {
arraytype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindChan:
type u struct {
chantype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindMap:
type u struct {
maptype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
case kindInterface:
type u struct {
interfacetype
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
default:
type u struct {
_type
u uncommontype
}
return &(*u)(unsafe.Pointer(t)).u
}
}
func (t *_type) name() string {
if t.tflag&tflagNamed == 0 {
return ""
}
s := t.string()
i := len(s) - 1
for i >= 0 && s[i] != '.' {
i--
}
return s[i+1:]
}
// pkgpath returns the path of the package where t was defined, if
// available. This is not the same as the reflect package's PkgPath
// method, in that it returns the package path for struct and interface
// types, not just named types.
func (t *_type) pkgpath() string {
if u := t.uncommon(); u != nil {
return t.nameOff(u.pkgpath).name()
}
switch t.kind & kindMask {
case kindStruct:
st := (*structtype)(unsafe.Pointer(t))
return st.pkgPath.name()
case kindInterface:
it := (*interfacetype)(unsafe.Pointer(t))
return it.pkgpath.name()
}
return ""
}
// reflectOffs holds type offsets defined at run time by the reflect package.
//
// When a type is defined at run time, its *rtype data lives on the heap.
// There are a wide range of possible addresses the heap may use, that
// may not be representable as a 32-bit offset. Moreover the GC may
// one day start moving heap memory, in which case there is no stable
// offset that can be defined.
//
// To provide stable offsets, we add pin *rtype objects in a global map
// and treat the offset as an identifier. We use negative offsets that
// do not overlap with any compile-time module offsets.
//
// Entries are created by reflect.addReflectOff.
var reflectOffs struct {
lock mutex
next int32
m map[int32]unsafe.Pointer
minv map[unsafe.Pointer]int32
}
func reflectOffsLock() {
lock(&reflectOffs.lock)
if raceenabled {
raceacquire(unsafe.Pointer(&reflectOffs.lock))
}
}
func reflectOffsUnlock() {
if raceenabled {
racerelease(unsafe.Pointer(&reflectOffs.lock))
}
unlock(&reflectOffs.lock)
}
func resolveNameOff(ptrInModule unsafe.Pointer, off nameOff) name {
if off == 0 {
return name{}
}
base := uintptr(ptrInModule)
for md := &firstmoduledata; md != nil; md = md.next {
if base >= md.types && base < md.etypes {
res := md.types + uintptr(off)
if res > md.etypes {
println("runtime: nameOff", hex(off), "out of range", hex(md.types), "-", hex(md.etypes))
throw("runtime: name offset out of range")
}
return name{(*byte)(unsafe.Pointer(res))}
}
}
// No module found. see if it is a run time name.
reflectOffsLock()
res, found := reflectOffs.m[int32(off)]
reflectOffsUnlock()
if !found {
println("runtime: nameOff", hex(off), "base", hex(base), "not in ranges:")
for next := &firstmoduledata; next != nil; next = next.next {
println("\ttypes", hex(next.types), "etypes", hex(next.etypes))
}
throw("runtime: name offset base pointer out of range")
}
return name{(*byte)(res)}
}
func (t *_type) nameOff(off nameOff) name {
return resolveNameOff(unsafe.Pointer(t), off)
}
func resolveTypeOff(ptrInModule unsafe.Pointer, off typeOff) *_type {
if off == 0 {
return nil
}
base := uintptr(ptrInModule)
var md *moduledata
for next := &firstmoduledata; next != nil; next = next.next {
if base >= next.types && base < next.etypes {
md = next
break
}
}
if md == nil {
reflectOffsLock()
res := reflectOffs.m[int32(off)]
reflectOffsUnlock()
if res == nil {
println("runtime: typeOff", hex(off), "base", hex(base), "not in ranges:")
for next := &firstmoduledata; next != nil; next = next.next {
println("\ttypes", hex(next.types), "etypes", hex(next.etypes))
}
throw("runtime: type offset base pointer out of range")
}
return (*_type)(res)
}
if t := md.typemap[off]; t != nil {
return t
}
res := md.types + uintptr(off)
if res > md.etypes {
println("runtime: typeOff", hex(off), "out of range", hex(md.types), "-", hex(md.etypes))
throw("runtime: type offset out of range")
}
return (*_type)(unsafe.Pointer(res))
}
func (t *_type) typeOff(off typeOff) *_type {
return resolveTypeOff(unsafe.Pointer(t), off)
}
func (t *_type) textOff(off textOff) unsafe.Pointer {
base := uintptr(unsafe.Pointer(t))
var md *moduledata
for next := &firstmoduledata; next != nil; next = next.next {
if base >= next.types && base < next.etypes {
md = next
break
}
}
if md == nil {
reflectOffsLock()
res := reflectOffs.m[int32(off)]
reflectOffsUnlock()
if res == nil {
println("runtime: textOff", hex(off), "base", hex(base), "not in ranges:")
for next := &firstmoduledata; next != nil; next = next.next {
println("\ttypes", hex(next.types), "etypes", hex(next.etypes))
}
throw("runtime: text offset base pointer out of range")
}
return res
}
res := uintptr(0)
// The text, or instruction stream is generated as one large buffer. The off (offset) for a method is
// its offset within this buffer. If the total text size gets too large, there can be issues on platforms like ppc64 if
// the target of calls are too far for the call instruction. To resolve the large text issue, the text is split
// into multiple text sections to allow the linker to generate long calls when necessary. When this happens, the vaddr
// for each text section is set to its offset within the text. Each method's offset is compared against the section
// vaddrs and sizes to determine the containing section. Then the section relative offset is added to the section's
// relocated baseaddr to compute the method addess.
if len(md.textsectmap) > 1 {
for i := range md.textsectmap {
sectaddr := md.textsectmap[i].vaddr
sectlen := md.textsectmap[i].length
if uintptr(off) >= sectaddr && uintptr(off) < sectaddr+sectlen {
res = md.textsectmap[i].baseaddr + uintptr(off) - uintptr(md.textsectmap[i].vaddr)
break
}
}
} else {
// single text section
res = md.text + uintptr(off)
}
if res > md.etext && GOARCH != "wasm" { // on wasm, functions do not live in the same address space as the linear memory
println("runtime: textOff", hex(off), "out of range", hex(md.text), "-", hex(md.etext))
throw("runtime: text offset out of range")
}
return unsafe.Pointer(res)
}
func (t *functype) in() []*_type {
// See funcType in reflect/type.go for details on data layout.
uadd := uintptr(unsafe.Sizeof(functype{}))
if t.typ.tflag&tflagUncommon != 0 {
uadd += unsafe.Sizeof(uncommontype{})
}
return (*[1 << 20]*_type)(add(unsafe.Pointer(t), uadd))[:t.inCount]
}
func (t *functype) out() []*_type {
// See funcType in reflect/type.go for details on data layout.
uadd := uintptr(unsafe.Sizeof(functype{}))
if t.typ.tflag&tflagUncommon != 0 {
uadd += unsafe.Sizeof(uncommontype{})
}
outCount := t.outCount & (1<<15 - 1)
return (*[1 << 20]*_type)(add(unsafe.Pointer(t), uadd))[t.inCount : t.inCount+outCount]
}
func (t *functype) dotdotdot() bool {
return t.outCount&(1<<15) != 0
}
type nameOff int32
type typeOff int32
type textOff int32
type method struct {
name nameOff
mtyp typeOff
ifn textOff
tfn textOff
}
type uncommontype struct {
pkgpath nameOff
mcount uint16 // number of methods
xcount uint16 // number of exported methods
moff uint32 // offset from this uncommontype to [mcount]method
_ uint32 // unused
}
type imethod struct {
name nameOff
ityp typeOff
}
type interfacetype struct {
typ _type
pkgpath name
mhdr []imethod
}
type maptype struct {
typ _type
key *_type
elem *_type
bucket *_type // internal type representing a hash bucket
keysize uint8 // size of key slot
elemsize uint8 // size of elem slot
bucketsize uint16 // size of bucket
flags uint32
}
// Note: flag values must match those used in the TMAP case
// in ../cmd/compile/internal/gc/reflect.go:dtypesym.
func (mt *maptype) indirectkey() bool { // store ptr to key instead of key itself
return mt.flags&1 != 0
}
func (mt *maptype) indirectelem() bool { // store ptr to elem instead of elem itself
return mt.flags&2 != 0
}
func (mt *maptype) reflexivekey() bool { // true if k==k for all keys
return mt.flags&4 != 0
}
func (mt *maptype) needkeyupdate() bool { // true if we need to update key on an overwrite
return mt.flags&8 != 0
}
func (mt *maptype) hashMightPanic() bool { // true if hash function might panic
return mt.flags&16 != 0
}
type arraytype struct {
typ _type
elem *_type
slice *_type
len uintptr
}
type chantype struct {
typ _type
elem *_type
dir uintptr
}
type slicetype struct {
typ _type
elem *_type
}
type functype struct {
typ _type
inCount uint16
outCount uint16
}
type ptrtype struct {
typ _type
elem *_type
}
type structfield struct {
name name
typ *_type
offsetAnon uintptr
}
func (f *structfield) offset() uintptr {
return f.offsetAnon >> 1
}
type structtype struct {
typ _type
pkgPath name
fields []structfield
}
// name is an encoded type name with optional extra data.
// See reflect/type.go for details.
type name struct {
bytes *byte
}
func (n name) data(off int) *byte {
return (*byte)(add(unsafe.Pointer(n.bytes), uintptr(off)))
}
func (n name) isExported() bool {
return (*n.bytes)&(1<<0) != 0
}
func (n name) nameLen() int {
return int(uint16(*n.data(1))<<8 | uint16(*n.data(2)))
}
func (n name) tagLen() int {
if *n.data(0)&(1<<1) == 0 {
return 0
}
off := 3 + n.nameLen()
return int(uint16(*n.data(off))<<8 | uint16(*n.data(off + 1)))
}
func (n name) name() (s string) {
if n.bytes == nil {
return ""
}
nl := n.nameLen()
if nl == 0 {
return ""
}
hdr := (*stringStruct)(unsafe.Pointer(&s))
hdr.str = unsafe.Pointer(n.data(3))
hdr.len = nl
return s
}
func (n name) tag() (s string) {
tl := n.tagLen()
if tl == 0 {
return ""
}
nl := n.nameLen()
hdr := (*stringStruct)(unsafe.Pointer(&s))
hdr.str = unsafe.Pointer(n.data(3 + nl + 2))
hdr.len = tl
return s
}
func (n name) pkgPath() string {
if n.bytes == nil || *n.data(0)&(1<<2) == 0 {
return ""
}
off := 3 + n.nameLen()
if tl := n.tagLen(); tl > 0 {
off += 2 + tl
}
var nameOff nameOff
copy((*[4]byte)(unsafe.Pointer(&nameOff))[:], (*[4]byte)(unsafe.Pointer(n.data(off)))[:])
pkgPathName := resolveNameOff(unsafe.Pointer(n.bytes), nameOff)
return pkgPathName.name()
}
// typelinksinit scans the types from extra modules and builds the
// moduledata typemap used to de-duplicate type pointers.
func typelinksinit() {
if firstmoduledata.next == nil {
return
}
typehash := make(map[uint32][]*_type, len(firstmoduledata.typelinks))
modules := activeModules()
prev := modules[0]
for _, md := range modules[1:] {
// Collect types from the previous module into typehash.
collect:
for _, tl := range prev.typelinks {
var t *_type
if prev.typemap == nil {
t = (*_type)(unsafe.Pointer(prev.types + uintptr(tl)))
} else {
t = prev.typemap[typeOff(tl)]
}
// Add to typehash if not seen before.
tlist := typehash[t.hash]
for _, tcur := range tlist {
if tcur == t {
continue collect
}
}
typehash[t.hash] = append(tlist, t)
}
if md.typemap == nil {
// If any of this module's typelinks match a type from a
// prior module, prefer that prior type by adding the offset
// to this module's typemap.
tm := make(map[typeOff]*_type, len(md.typelinks))
pinnedTypemaps = append(pinnedTypemaps, tm)
md.typemap = tm
for _, tl := range md.typelinks {
t := (*_type)(unsafe.Pointer(md.types + uintptr(tl)))
for _, candidate := range typehash[t.hash] {
seen := map[_typePair]struct{}{}
if typesEqual(t, candidate, seen) {
t = candidate
break
}
}
md.typemap[typeOff(tl)] = t
}
}
prev = md
}
}
type _typePair struct {
t1 *_type
t2 *_type
}
// typesEqual reports whether two types are equal.
//
// Everywhere in the runtime and reflect packages, it is assumed that
// there is exactly one *_type per Go type, so that pointer equality
// can be used to test if types are equal. There is one place that
// breaks this assumption: buildmode=shared. In this case a type can
// appear as two different pieces of memory. This is hidden from the
// runtime and reflect package by the per-module typemap built in
// typelinksinit. It uses typesEqual to map types from later modules
// back into earlier ones.
//
// Only typelinksinit needs this function.
func typesEqual(t, v *_type, seen map[_typePair]struct{}) bool {
tp := _typePair{t, v}
if _, ok := seen[tp]; ok {
return true
}
// mark these types as seen, and thus equivalent which prevents an infinite loop if
// the two types are identical, but recursively defined and loaded from
// different modules
seen[tp] = struct{}{}
if t == v {
return true
}
kind := t.kind & kindMask
if kind != v.kind&kindMask {
return false
}
if t.string() != v.string() {
return false
}
ut := t.uncommon()
uv := v.uncommon()
if ut != nil || uv != nil {
if ut == nil || uv == nil {
return false
}
pkgpatht := t.nameOff(ut.pkgpath).name()
pkgpathv := v.nameOff(uv.pkgpath).name()
if pkgpatht != pkgpathv {
return false
}
}
if kindBool <= kind && kind <= kindComplex128 {
return true
}
switch kind {
case kindString, kindUnsafePointer:
return true
case kindArray:
at := (*arraytype)(unsafe.Pointer(t))
av := (*arraytype)(unsafe.Pointer(v))
return typesEqual(at.elem, av.elem, seen) && at.len == av.len
case kindChan:
ct := (*chantype)(unsafe.Pointer(t))
cv := (*chantype)(unsafe.Pointer(v))
return ct.dir == cv.dir && typesEqual(ct.elem, cv.elem, seen)
case kindFunc:
ft := (*functype)(unsafe.Pointer(t))
fv := (*functype)(unsafe.Pointer(v))
if ft.outCount != fv.outCount || ft.inCount != fv.inCount {
return false
}
tin, vin := ft.in(), fv.in()
for i := 0; i < len(tin); i++ {
if !typesEqual(tin[i], vin[i], seen) {
return false
}
}
tout, vout := ft.out(), fv.out()
for i := 0; i < len(tout); i++ {
if !typesEqual(tout[i], vout[i], seen) {
return false
}
}
return true
case kindInterface:
it := (*interfacetype)(unsafe.Pointer(t))
iv := (*interfacetype)(unsafe.Pointer(v))
if it.pkgpath.name() != iv.pkgpath.name() {
return false
}
if len(it.mhdr) != len(iv.mhdr) {
return false
}
for i := range it.mhdr {
tm := &it.mhdr[i]
vm := &iv.mhdr[i]
// Note the mhdr array can be relocated from
// another module. See #17724.
tname := resolveNameOff(unsafe.Pointer(tm), tm.name)
vname := resolveNameOff(unsafe.Pointer(vm), vm.name)
if tname.name() != vname.name() {
return false
}
if tname.pkgPath() != vname.pkgPath() {
return false
}
tityp := resolveTypeOff(unsafe.Pointer(tm), tm.ityp)
vityp := resolveTypeOff(unsafe.Pointer(vm), vm.ityp)
if !typesEqual(tityp, vityp, seen) {
return false
}
}
return true
case kindMap:
mt := (*maptype)(unsafe.Pointer(t))
mv := (*maptype)(unsafe.Pointer(v))
return typesEqual(mt.key, mv.key, seen) && typesEqual(mt.elem, mv.elem, seen)
case kindPtr:
pt := (*ptrtype)(unsafe.Pointer(t))
pv := (*ptrtype)(unsafe.Pointer(v))
return typesEqual(pt.elem, pv.elem, seen)
case kindSlice:
st := (*slicetype)(unsafe.Pointer(t))
sv := (*slicetype)(unsafe.Pointer(v))
return typesEqual(st.elem, sv.elem, seen)
case kindStruct:
st := (*structtype)(unsafe.Pointer(t))
sv := (*structtype)(unsafe.Pointer(v))
if len(st.fields) != len(sv.fields) {
return false
}
if st.pkgPath.name() != sv.pkgPath.name() {
return false
}
for i := range st.fields {
tf := &st.fields[i]
vf := &sv.fields[i]
if tf.name.name() != vf.name.name() {
return false
}
if !typesEqual(tf.typ, vf.typ, seen) {
return false
}
if tf.name.tag() != vf.name.tag() {
return false
}
if tf.offsetAnon != vf.offsetAnon {
return false
}
}
return true
default:
println("runtime: impossible type kind", kind)
throw("runtime: impossible type kind")
return false
}
}
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