Add dependencies/vendor (whatsapp)

1 files changed, 1022 insertions, 0 deletions

diff --git a/vendor/modernc.org/cc/v3/abi.go b/vendor/modernc.org/cc/v3/abi.go
new file mode 100644
index 00000000..e0325584
--- /dev/null
+++ b/vendor/modernc.org/cc/v3/abi.go
@@ -0,0 +1,1022 @@
+// Copyright 2019 The CC 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 cc // import "modernc.org/cc/v3"
+
+import (
+	"encoding/binary"
+	"fmt"
+	"math"
+	"os"
+	"runtime"
+
+	"lukechampine.com/uint128"
+	"modernc.org/mathutil"
+)
+
+var (
+	idAligned   = String("aligned")
+	idGCCStruct = String("gcc_struct")
+	idMSStruct  = String("ms_struct")
+	idPacked    = String("packed")
+
+	complexTypedefs = map[StringID]Kind{
+		dict.sid("__COMPLEX_CHAR_TYPE__"):               ComplexChar,
+		dict.sid("__COMPLEX_DOUBLE_TYPE__"):             ComplexDouble,
+		dict.sid("__COMPLEX_FLOAT_TYPE__"):              ComplexFloat,
+		dict.sid("__COMPLEX_INT_TYPE__"):                ComplexInt,
+		dict.sid("__COMPLEX_LONG_TYPE__"):               ComplexLong,
+		dict.sid("__COMPLEX_LONG_DOUBLE_TYPE__"):        ComplexLongDouble,
+		dict.sid("__COMPLEX_LONG_LONG_TYPE__"):          ComplexLongLong,
+		dict.sid("__COMPLEX_SHORT_TYPE__"):              ComplexShort,
+		dict.sid("__COMPLEX_UNSIGNED_TYPE__"):           ComplexUInt,
+		dict.sid("__COMPLEX_LONG_UNSIGNED_TYPE__"):      ComplexULong,
+		dict.sid("__COMPLEX_LONG_LONG_UNSIGNED_TYPE__"): ComplexULongLong,
+		dict.sid("__COMPLEX_SHORT_UNSIGNED_TYPE__"):     ComplexUShort,
+	}
+)
+
+// NewABI creates an ABI for a given OS and architecture. The OS and architecture values are the same as used in Go.
+// The ABI type map may miss advanced types like complex numbers, etc. If the os/arch pair is not recognized, a
+// *ErrUnsupportedOSArch is returned.
+func NewABI(os, arch string) (ABI, error) {
+	order, ok := abiByteOrders[arch]
+	if !ok {
+		return ABI{}, fmt.Errorf("unsupported arch: %s", arch)
+	}
+	types, ok := abiTypes[[2]string{os, arch}]
+	if !ok {
+		return ABI{}, fmt.Errorf("unsupported os/arch pair: %s-%s", os, arch)
+	}
+	abi := ABI{
+		ByteOrder:  order,
+		Types:      make(map[Kind]ABIType, len(types)),
+		SignedChar: abiSignedChar[[2]string{os, arch}],
+		os:         os,
+		arch:       arch,
+	}
+	// copy the map, so it can be modified by user
+	for k, v := range types {
+		abi.Types[k] = v
+	}
+	return abi, nil
+}
+
+// NewABIFromEnv uses GOOS and GOARCH values to create a corresponding ABI.
+// If those environment variables are not set, an OS/arch of a Go runtime is used.
+// It returns a *ErrUnsupportedOSArch if OS/arch pair is not supported.
+func NewABIFromEnv() (ABI, error) {
+	osv := os.Getenv("GOOS")
+	if osv == "" {
+		osv = runtime.GOOS
+	}
+	arch := os.Getenv("GOARCH")
+	if arch == "" {
+		arch = runtime.GOARCH
+	}
+	return NewABI(osv, arch)
+}
+
+// ABIType describes properties of a non-aggregate type.
+type ABIType struct {
+	Size       uintptr
+	Align      int
+	FieldAlign int
+}
+
+// ABI describes selected parts of the Application Binary Interface.
+type ABI struct {
+	ByteOrder binary.ByteOrder
+	Types     map[Kind]ABIType
+	arch      string
+	os        string
+	types     map[Kind]Type
+
+	SignedChar bool
+}
+
+func (a *ABI) sanityCheck(ctx *context, intMaxWidth int, s Scope) error {
+	if intMaxWidth == 0 {
+		intMaxWidth = 64
+	}
+
+	a.types = map[Kind]Type{}
+	for _, k := range []Kind{
+		Bool,
+		Char,
+		Double,
+		Enum,
+		Float,
+		Int,
+		Long,
+		LongDouble,
+		LongLong,
+		Ptr,
+		SChar,
+		Short,
+		UChar,
+		UInt,
+		ULong,
+		ULongLong,
+		UShort,
+		Void,
+	} {
+		v, ok := a.Types[k]
+		if !ok {
+			if ctx.err(noPos, "ABI is missing %s", k) {
+				return ctx.Err()
+			}
+
+			continue
+		}
+
+		if (k != Void && v.Size == 0) || v.Align == 0 || v.FieldAlign == 0 ||
+			v.Align > math.MaxUint8 || v.FieldAlign > math.MaxUint8 {
+			if ctx.err(noPos, "invalid ABI type %s: %+v", k, v) {
+				return ctx.Err()
+			}
+		}
+
+		if integerTypes[k] && v.Size > 8 {
+			if ctx.err(noPos, "invalid ABI type %s size: %v, must be <= 8", k, v.Size) {
+				return ctx.Err()
+			}
+		}
+		var f flag
+		if integerTypes[k] && a.isSignedInteger(k) {
+			f = fSigned
+		}
+		t := &typeBase{
+			align:      byte(a.align(k)),
+			fieldAlign: byte(a.fieldAlign(k)),
+			flags:      f,
+			kind:       byte(k),
+			size:       uintptr(a.size(k)),
+		}
+		a.types[k] = t
+	}
+	if _, ok := a.Types[Int128]; ok {
+		t := &typeBase{
+			align:      byte(a.align(Int128)),
+			fieldAlign: byte(a.fieldAlign(Int128)),
+			flags:      fSigned,
+			kind:       byte(Int128),
+			size:       uintptr(a.size(Int128)),
+		}
+		a.types[Int128] = t
+	}
+	if _, ok := a.Types[UInt128]; ok {
+		t := &typeBase{
+			align:      byte(a.align(UInt128)),
+			fieldAlign: byte(a.fieldAlign(UInt128)),
+			kind:       byte(UInt128),
+			size:       uintptr(a.size(UInt128)),
+		}
+		a.types[UInt128] = t
+	}
+	return ctx.Err()
+}
+
+func (a *ABI) Type(k Kind) Type { return a.types[k] }
+
+func (a *ABI) align(k Kind) int      { return a.Types[k].Align }
+func (a *ABI) fieldAlign(k Kind) int { return a.Types[k].FieldAlign }
+func (a *ABI) size(k Kind) int       { return int(a.Types[k].Size) }
+
+func (a *ABI) isSignedInteger(k Kind) bool {
+	if !integerTypes[k] {
+		internalError()
+	}
+
+	switch k {
+	case Bool, UChar, UInt, ULong, ULongLong, UShort:
+		return false
+	case Char:
+		return a.SignedChar
+	default:
+		return true
+	}
+}
+
+func roundup(n, to int64) int64 {
+	if r := n % to; r != 0 {
+		return n + to - r
+	}
+
+	return n
+}
+
+func roundup128(n uint128.Uint128, to uint64) uint128.Uint128 {
+	if r := n.Mod(uint128.From64(to)); !r.IsZero() {
+		return n.Add64(to).Sub(r)
+	}
+
+	return n
+}
+
+func rounddown(n, to int64) int64 {
+	return n &^ (to - 1)
+}
+
+func rounddown128(n uint128.Uint128, to uint64) uint128.Uint128 {
+	return n.And(uint128.Uint128{Hi: ^uint64(0), Lo: ^(to - 1)})
+}
+
+func normalizeBitFieldWidth(n byte) byte {
+	switch {
+	case n <= 8:
+		return 8
+	case n <= 16:
+		return 16
+	case n <= 32:
+		return 32
+	case n <= 64:
+		return 64
+	default:
+		panic(todo("internal error: %v", n))
+	}
+}
+
+func (a *ABI) layout(ctx *context, n Node, t *structType) *structType {
+	if t == nil {
+		return nil
+	}
+
+	if t.typeBase.align < 1 {
+		t.typeBase.align = 1
+	}
+	for _, v := range t.attr {
+		if _, ok := v.Has(idGCCStruct); ok {
+			return a.gccLayout(ctx, n, t)
+		}
+
+		//TODO if _, ok := v.Has(idMSStruct); ok {
+		//TODO 	return a.msLayout(ctx, n, t)
+		//TODO }
+	}
+
+	switch {
+	case ctx.cfg.Config3.GCCStructs:
+		return a.gccLayout(ctx, n, t)
+		//TODO case ctx.cfg.Config3.MSStructs:
+		//TODO 	return a.msLayout(ctx, n, t)
+	}
+
+	var hasBitfields bool
+
+	defer func() {
+		if !hasBitfields {
+			return
+		}
+
+		m := make(map[uintptr][]*field, len(t.fields))
+		for _, f := range t.fields {
+			off := f.offset
+			m[off] = append(m[off], f)
+		}
+		for _, s := range m {
+			var first *field
+			var w byte
+			for _, f := range s {
+				if first == nil {
+					first = f
+				}
+				if f.isBitField {
+					n := f.bitFieldOffset + f.bitFieldWidth
+					if n > w {
+						w = n
+					}
+				}
+			}
+			w = normalizeBitFieldWidth(w)
+			for _, f := range s {
+				if f.isBitField {
+					f.blockStart = first
+					f.blockWidth = w
+				}
+				if a.ByteOrder == binary.BigEndian {
+					f.bitFieldOffset = w - f.bitFieldWidth - f.bitFieldOffset
+					f.bitFieldMask = (uint64(1)<<f.bitFieldWidth - 1) << f.bitFieldOffset
+				}
+			}
+		}
+	}()
+
+	var off int64 // bit offset
+	align := int(t.typeBase.align)
+
+	switch {
+	case t.Kind() == Union:
+		for _, f := range t.fields {
+			ft := f.Type()
+			sz := ft.Size()
+			if n := int64(8 * sz); n > off {
+				off = n
+			}
+			al := ft.FieldAlign()
+			if al == 0 {
+				al = 1
+			}
+			if al > align {
+				align = al
+			}
+
+			if f.isBitField {
+				hasBitfields = true
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+			}
+			f.promote = integerPromotion(a, ft)
+		}
+		t.align = byte(align)
+		t.fieldAlign = byte(align)
+		off = roundup(off, 8*int64(align))
+		t.size = uintptr(off >> 3)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	default:
+		var i int
+		var group byte
+		var f, lf *field
+		for i, f = range t.fields {
+			ft := f.Type()
+			var sz uintptr
+			switch {
+			case ft.Kind() == Array && i == len(t.fields)-1:
+				if ft.IsIncomplete() || ft.Len() == 0 {
+					t.hasFlexibleMember = true
+					f.isFlexible = true
+					break
+				}
+
+				fallthrough
+			default:
+				sz = ft.Size()
+			}
+
+			bitSize := 8 * int(sz)
+			al := ft.FieldAlign()
+			if al == 0 {
+				al = 1
+			}
+			if al > align {
+				align = al
+			}
+
+			switch {
+			case f.isBitField:
+				hasBitfields = true
+				eal := 8 * al
+				if eal < bitSize {
+					eal = bitSize
+				}
+				down := off &^ (int64(eal) - 1)
+				bitoff := off - down
+				downMax := off &^ (int64(bitSize) - 1)
+				skip := lf != nil && lf.isBitField && lf.bitFieldWidth == 0 ||
+					lf != nil && lf.bitFieldWidth == 0 && ctx.cfg.NoFieldAndBitfieldOverlap
+				switch {
+				case skip || int(off-downMax)+int(f.bitFieldWidth) > bitSize:
+					group = 0
+					off = roundup(off, 8*int64(al))
+					f.offset = uintptr(off >> 3)
+					f.bitFieldOffset = 0
+					f.bitFieldMask = 1<<f.bitFieldWidth - 1
+					off += int64(f.bitFieldWidth)
+					if f.bitFieldWidth == 0 {
+						lf = f
+						continue
+					}
+				default:
+					f.offset = uintptr(down >> 3)
+					f.bitFieldOffset = byte(bitoff)
+					f.bitFieldMask = (1<<f.bitFieldWidth - 1) << byte(bitoff)
+					off += int64(f.bitFieldWidth)
+				}
+				group += f.bitFieldWidth
+			default:
+				if n := group % 64; n != 0 {
+					group -= n
+					off += int64(normalizeBitFieldWidth(group) - group)
+				}
+				off0 := off
+				off = roundup(off, 8*int64(al))
+				f.pad = byte(off-off0) >> 3
+				f.offset = uintptr(off) >> 3
+				off += 8 * int64(sz)
+				group = 0
+			}
+			f.promote = integerPromotion(a, ft)
+			lf = f
+		}
+		t.align = byte(align)
+		t.fieldAlign = byte(align)
+		off0 := off
+		off = roundup(off, 8*int64(align))
+		if f != nil && !f.IsBitField() {
+			f.pad = byte(off-off0) >> 3
+		}
+		t.size = uintptr(off >> 3)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	}
+	return t
+}
+
+func (a *ABI) Ptr(n Node, t Type) Type {
+	base := t.base()
+	base.align = byte(a.align(Ptr))
+	base.fieldAlign = byte(a.fieldAlign(Ptr))
+	base.kind = byte(Ptr)
+	base.size = uintptr(a.size(Ptr))
+	base.flags &^= fIncomplete
+	return &pointerType{
+		elem:     t,
+		typeBase: base,
+	}
+}
+
+func (a *ABI) gccLayout(ctx *context, n Node, t *structType) (r *structType) {
+	if t.IsPacked() {
+		return a.gccPackedLayout(ctx, n, t)
+	}
+
+	if t.Kind() == Union {
+		var off uint128.Uint128 // In bits.
+		align := int(t.typeBase.align)
+		for _, f := range t.fields {
+			switch {
+			case f.isBitField:
+				f.offset = 0
+				f.bitFieldOffset = 0
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+				if uint64(f.bitFieldWidth) > off.Lo {
+					off.Lo = uint64(f.bitFieldWidth)
+				}
+			default:
+				al := f.Type().Align()
+				if al > align {
+					align = al
+				}
+				f.offset = 0
+				off2 := uint128.From64(uint64(f.Type().Size())).Mul64(8)
+				if off2.Cmp(off) > 0 {
+					off = off2
+				}
+			}
+			f.promote = integerPromotion(a, f.Type())
+		}
+		t.align = byte(align)
+		t.fieldAlign = byte(align)
+		off = roundup128(off, 8*uint64(align))
+		t.size = uintptr(off.Rsh(3).Lo)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+		return t
+	}
+
+	var off uint128.Uint128 // In bits.
+	align := int(t.typeBase.align)
+	for i, f := range t.fields {
+		switch {
+		case f.isBitField:
+			al := f.Type().Align()
+
+			// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
+
+			// 1. Jump backwards to nearest address that would support this type. For
+			// example if we have an int jump to the closest address where an int could be
+			// stored according to the platform alignment rules.
+			down := rounddown128(off, 8*uint64(al))
+
+			// 2. Get sizeof(current field) bytes from that address.
+			alloc := int64(f.Type().Size()) * 8
+			need := int64(f.bitFieldWidth)
+			if need == 0 && i != 0 {
+				off = roundup128(off, 8*uint64(al))
+				continue
+			}
+
+			if al > align {
+				align = al
+			}
+			used := int64(off.Sub(down).Lo)
+			switch {
+			case alloc-used >= need:
+				// 3. If the number of bits that we need to store can be stored in these bits,
+				// put the bits in the lowest possible bits of this block.
+				off = down.Add64(uint64(used))
+				f.offset = uintptr(down.Rsh(3).Lo)
+				f.bitFieldOffset = byte(used)
+				f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
+				off = off.Add64(uint64(f.bitFieldWidth))
+				f.promote = integerPromotion(a, f.Type())
+			default:
+				// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
+				// make up this bit-field in the lowest bits of the next block.
+				off = roundup128(off, 8*uint64(al))
+				f.offset = uintptr(off.Rsh(3).Lo)
+				f.bitFieldOffset = 0
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+				off = off.Add64(uint64(f.bitFieldWidth))
+				f.promote = integerPromotion(a, f.Type())
+			}
+		default:
+			al := f.Type().Align()
+			if al > align {
+				align = al
+			}
+			off = roundup128(off, 8*uint64(al))
+			f.offset = uintptr(off.Rsh(3).Lo)
+			sz := uint128.From64(uint64(f.Type().Size()))
+			off = off.Add(sz.Mul64(8))
+			f.promote = integerPromotion(a, f.Type())
+		}
+	}
+	var lf *field
+	for _, f := range t.fields {
+		if lf != nil && !lf.isBitField && !f.isBitField {
+			lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
+		}
+		lf = f
+	}
+	t.align = byte(align)
+	t.fieldAlign = byte(align)
+	off0 := off
+	off = roundup128(off, 8*uint64(align))
+	if lf != nil && !lf.IsBitField() {
+		lf.pad = byte(off.Sub(off0).Rsh(3).Lo)
+	}
+	t.size = uintptr(off.Rsh(3).Lo)
+	ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	return t
+}
+
+func (a *ABI) gccPackedLayout(ctx *context, n Node, t *structType) (r *structType) {
+	switch a.arch {
+	case "arm", "arm64":
+		return a.gccPackedLayoutARM(ctx, n, t)
+	}
+
+	if t.typeBase.flags&fAligned == 0 {
+		t.align = 1
+	}
+	t.fieldAlign = t.align
+	if t.Kind() == Union {
+		var off int64 // In bits.
+		for _, f := range t.fields {
+			switch {
+			case f.isBitField:
+				panic(todo("%v: ", n.Position()))
+			default:
+				f.offset = 0
+				if off2 := 8 * int64(f.Type().Size()); off2 > off {
+					off = off2
+				}
+				f.promote = integerPromotion(a, f.Type())
+			}
+		}
+		off = roundup(off, 8)
+		t.size = uintptr(off >> 3)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+		return t
+	}
+
+	var off int64 // In bits.
+	for i, f := range t.fields {
+		switch {
+		case f.isBitField:
+			if f.bitFieldWidth == 0 {
+				if i != 0 {
+					off = roundup(off, 8*int64(f.Type().Align()))
+				}
+				continue
+			}
+
+			if b := f.Type().base(); b.flags&fAligned != 0 {
+				off = roundup(off, 8*int64(a.Types[f.Type().Kind()].Align))
+			}
+			f.offset = uintptr(off >> 3)
+			f.bitFieldOffset = byte(off & 7)
+			f.bitFieldMask = (1<<f.bitFieldWidth - 1) << f.bitFieldOffset
+			off += int64(f.bitFieldWidth)
+			f.promote = integerPromotion(a, f.Type())
+		default:
+			al := f.Type().Align()
+			off = roundup(off, 8*int64(al))
+			f.offset = uintptr(off) >> 3
+			off += 8 * int64(f.Type().Size())
+			f.promote = integerPromotion(a, f.Type())
+		}
+	}
+	var lf *field
+	for _, f := range t.fields {
+		if lf != nil && !lf.isBitField && !f.isBitField {
+			lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
+		}
+		lf = f
+	}
+	off0 := off
+	off = roundup(off, 8*int64(t.Align()))
+	if lf != nil && !lf.IsBitField() {
+		lf.pad = byte(off-off0) >> 3
+	}
+	t.size = uintptr(off >> 3)
+	ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	return t
+}
+
+func (a *ABI) gccPackedLayoutARM(ctx *context, n Node, t *structType) (r *structType) {
+	align := 1
+	if t.typeBase.flags&fAligned == 0 {
+		t.align = 1
+	}
+	t.fieldAlign = t.align
+	if t.Kind() == Union {
+		var off int64 // In bits.
+		for _, f := range t.fields {
+			switch {
+			case f.isBitField:
+				panic(todo("%v: ", n.Position()))
+			default:
+				f.offset = 0
+				if off2 := 8 * int64(f.Type().Size()); off2 > off {
+					off = off2
+				}
+				f.promote = integerPromotion(a, f.Type())
+			}
+		}
+		off = roundup(off, 8)
+		t.size = uintptr(off >> 3)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+		return t
+	}
+
+	var off int64 // In bits.
+	for i, f := range t.fields {
+		switch {
+		case f.isBitField:
+			if f.bitFieldWidth == 0 {
+				al := f.Type().Align()
+				if al > align {
+					align = al
+				}
+				if i != 0 {
+					off = roundup(off, 8*int64(f.Type().Align()))
+				}
+				continue
+			}
+
+			if b := f.Type().base(); b.flags&fAligned != 0 {
+				off = roundup(off, 8*int64(a.Types[f.Type().Kind()].Align))
+			}
+			f.offset = uintptr(off >> 3)
+			f.bitFieldOffset = byte(off & 7)
+			f.bitFieldMask = (1<<f.bitFieldWidth - 1) << f.bitFieldOffset
+			off += int64(f.bitFieldWidth)
+			f.promote = integerPromotion(a, f.Type())
+		default:
+			al := f.Type().Align()
+			off = roundup(off, 8*int64(al))
+			f.offset = uintptr(off) >> 3
+			off += 8 * int64(f.Type().Size())
+			f.promote = integerPromotion(a, f.Type())
+		}
+	}
+	var lf *field
+	for _, f := range t.fields {
+		if lf != nil && !lf.isBitField && !f.isBitField {
+			lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
+		}
+		lf = f
+	}
+	if b := t.base(); b.flags&fAligned == 0 {
+		t.align = byte(align)
+		t.fieldAlign = byte(align)
+	}
+	off0 := off
+	off = roundup(off, 8*int64(t.Align()))
+	if lf != nil && !lf.IsBitField() {
+		lf.pad = byte(off-off0) >> 3
+	}
+	t.size = uintptr(off >> 3)
+	ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	return t
+}
+
+// https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html#x86-Options
+//
+//	-mno-ms-bitfields
+//
+// Enable/disable bit-field layout compatible with the native Microsoft Windows
+// compiler.
+//
+// If packed is used on a structure, or if bit-fields are used, it may be that
+// the Microsoft ABI lays out the structure differently than the way GCC
+// normally does. Particularly when moving packed data between functions
+// compiled with GCC and the native Microsoft compiler (either via function
+// call or as data in a file), it may be necessary to access either format.
+//
+// This option is enabled by default for Microsoft Windows targets. This
+// behavior can also be controlled locally by use of variable or type
+// attributes. For more information, see x86 Variable Attributes and x86 Type
+// Attributes.
+//
+// The Microsoft structure layout algorithm is fairly simple with the exception
+// of the bit-field packing. The padding and alignment of members of structures
+// and whether a bit-field can straddle a storage-unit boundary are determine
+// by these rules:
+//
+// Structure members are stored sequentially in the order in which they are
+// declared: the first member has the lowest memory address and the last member
+// the highest.  Every data object has an alignment requirement. The alignment
+// requirement for all data except structures, unions, and arrays is either the
+// size of the object or the current packing size (specified with either the
+// aligned attribute or the pack pragma), whichever is less. For structures,
+// unions, and arrays, the alignment requirement is the largest alignment
+// requirement of its members. Every object is allocated an offset so that:
+// offset % alignment_requirement == 0 Adjacent bit-fields are packed into the
+// same 1-, 2-, or 4-byte allocation unit if the integral types are the same
+// size and if the next bit-field fits into the current allocation unit without
+// crossing the boundary imposed by the common alignment requirements of the
+// bit-fields.  MSVC interprets zero-length bit-fields in the following ways:
+//
+// If a zero-length bit-field is inserted between two bit-fields that are
+// normally coalesced, the bit-fields are not coalesced.  For example:
+//
+// 	struct
+// 	 {
+// 	   unsigned long bf_1 : 12;
+// 	   unsigned long : 0;
+// 	   unsigned long bf_2 : 12;
+// 	 } t1;
+//
+// The size of t1 is 8 bytes with the zero-length bit-field. If the zero-length
+// bit-field were removed, t1’s size would be 4 bytes.
+//
+// If a zero-length bit-field is inserted after a bit-field, foo, and the
+// alignment of the zero-length bit-field is greater than the member that
+// follows it, bar, bar is aligned as the type of the zero-length bit-field.
+// For example:
+//
+// 	struct
+// 	 {
+// 	   char foo : 4;
+// 	   short : 0;
+// 	   char bar;
+// 	 } t2;
+//
+// 	struct
+// 	 {
+// 	   char foo : 4;
+// 	   short : 0;
+// 	   double bar;
+// 	 } t3;
+//
+// For t2, bar is placed at offset 2, rather than offset 1. Accordingly, the
+// size of t2 is 4. For t3, the zero-length bit-field does not affect the
+// alignment of bar or, as a result, the size of the structure.
+//
+// Taking this into account, it is important to note the following:
+//
+// If a zero-length bit-field follows a normal bit-field, the type of the
+// zero-length bit-field may affect the alignment of the structure as whole.
+// For example, t2 has a size of 4 bytes, since the zero-length bit-field
+// follows a normal bit-field, and is of type short.  Even if a zero-length
+// bit-field is not followed by a normal bit-field, it may still affect the
+// alignment of the structure:
+//
+// 	struct
+// 	 {
+// 	   char foo : 6;
+// 	   long : 0;
+// 	 } t4;
+//
+// Here, t4 takes up 4 bytes.
+//
+// Zero-length bit-fields following non-bit-field members are ignored:
+//
+// 	struct
+// 	 {
+// 	   char foo;
+// 	   long : 0;
+// 	   char bar;
+// 	 } t5;
+//
+// Here, t5 takes up 2 bytes.
+
+func (a *ABI) msLayout(ctx *context, n Node, t *structType) (r *structType) {
+	if t.IsPacked() {
+		return a.msPackedLayout(ctx, n, t)
+	}
+
+	if t.Kind() == Union {
+		panic(todo(""))
+	}
+
+	var off int64 // In bits.
+	align := int(t.typeBase.align)
+	var prev *field
+	for i, f := range t.fields {
+		switch {
+		case f.isBitField:
+			al := f.Type().Align()
+			if prev != nil {
+				switch {
+				case prev.isBitField && prev.Type().Size() != f.Type().Size():
+					off = roundup(off, 8*int64(prev.Type().Align()))
+					off = roundup(off, 8*int64(al))
+				case !prev.isBitField:
+					off = roundup(off, 8*int64(al))
+				default:
+					// Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation
+					// unit if the integral types are the same size and if the next bit-field fits
+					// into the current allocation unit without crossing the boundary imposed by
+					// the common alignment requirements of the bit-fields.
+				}
+			}
+
+			// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
+
+			// 1. Jump backwards to nearest address that would support this type. For
+			// example if we have an int jump to the closest address where an int could be
+			// stored according to the platform alignment rules.
+			down := rounddown(off, 8*int64(al))
+
+			// 2. Get sizeof(current field) bytes from that address.
+			alloc := int64(f.Type().Size()) * 8
+			need := int64(f.bitFieldWidth)
+			if need == 0 && i != 0 {
+				off = roundup(off, 8*int64(al))
+				continue
+			}
+
+			if al > align {
+				align = al
+			}
+			used := off - down
+			switch {
+			case alloc-used >= need:
+				// 3. If the number of bits that we need to store can be stored in these bits,
+				// put the bits in the lowest possible bits of this block.
+				off = down + used
+				f.offset = uintptr(down >> 3)
+				f.bitFieldOffset = byte(used)
+				f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
+				off += int64(f.bitFieldWidth)
+				f.promote = integerPromotion(a, f.Type())
+			default:
+				// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
+				// make up this bit-field in the lowest bits of the next block.
+				off = roundup(off, 8*int64(al))
+				f.offset = uintptr(off >> 3)
+				f.bitFieldOffset = 0
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+				off += int64(f.bitFieldWidth)
+				f.promote = integerPromotion(a, f.Type())
+			}
+		default:
+			if prev != nil && prev.isBitField {
+				off = roundup(off, 8*int64(prev.Type().Align()))
+			}
+			al := f.Type().Align()
+			if al > align {
+				align = al
+			}
+			off = roundup(off, 8*int64(al))
+			f.offset = uintptr(off) >> 3
+			off += 8 * int64(f.Type().Size())
+			f.promote = integerPromotion(a, f.Type())
+		}
+		prev = f
+	}
+	var lf *field
+	for _, f := range t.fields {
+		if lf != nil && !lf.isBitField && !f.isBitField {
+			lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
+		}
+		lf = f
+	}
+	t.align = byte(align)
+	t.fieldAlign = byte(align)
+	off0 := off
+	off = roundup(off, 8*int64(align))
+	if lf != nil && !lf.IsBitField() {
+		lf.pad = byte(off-off0) >> 3
+	}
+	t.size = uintptr(off >> 3)
+	ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	return t
+}
+
+func (a *ABI) msPackedLayout(ctx *context, n Node, t *structType) (r *structType) {
+	if t.typeBase.flags&fAligned == 0 {
+		t.align = 1
+	}
+	t.fieldAlign = t.align
+	if t.Kind() == Union {
+		panic(todo(""))
+		var off int64 // In bits.
+		for _, f := range t.fields {
+			switch {
+			case f.isBitField:
+				panic(todo("%v: ", n.Position()))
+			default:
+				f.offset = 0
+				if off2 := 8 * int64(f.Type().Size()); off2 > off {
+					off = off2
+				}
+				f.promote = integerPromotion(a, f.Type())
+			}
+		}
+		off = roundup(off, 8)
+		t.size = uintptr(off >> 3)
+		ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+		return t
+	}
+
+	var off int64 // In bits.
+	var prev *field
+	align := int(t.typeBase.align)
+	for i, f := range t.fields {
+	out:
+		switch {
+		case f.isBitField:
+			al := f.Type().Align()
+			switch {
+			case prev != nil && prev.IsBitField() && prev.Type().Size() != f.Type().Size():
+				off = mathutil.MaxInt64(off, int64(prev.Offset()*8)+int64(prev.BitFieldOffset()+8*prev.Type().Align()))
+				off = roundup(off, 8*int64(align))
+				f.offset = uintptr(off >> 3)
+				f.bitFieldOffset = 0
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+				off += int64(f.bitFieldWidth)
+				f.promote = integerPromotion(a, f.Type())
+				break out
+			}
+
+			// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
+
+			// 1. Jump backwards to nearest address that would support this type. For
+			// example if we have an int jump to the closest address where an int could be
+			// stored according to the platform alignment rules.
+			down := rounddown(off, 8*int64(al))
+
+			// 2. Get sizeof(current field) bytes from that address.
+			alloc := int64(f.Type().Size()) * 8
+			need := int64(f.bitFieldWidth)
+			if need == 0 && i != 0 {
+				off = roundup(off, 8*int64(al))
+				continue
+			}
+
+			used := off - down
+			switch {
+			case alloc-used >= need:
+				// 3. If the number of bits that we need to store can be stored in these bits,
+				// put the bits in the lowest possible bits of this block.
+				off = down + used
+				f.offset = uintptr(down >> 3)
+				f.bitFieldOffset = byte(used)
+				f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
+				off += int64(f.bitFieldWidth)
+				f.promote = integerPromotion(a, f.Type())
+			default:
+				// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
+				// make up this bit-field in the lowest bits of the next block.
+				off = roundup(off, 8*int64(al))
+				f.offset = uintptr(off >> 3)
+				f.bitFieldOffset = 0
+				f.bitFieldMask = 1<<f.bitFieldWidth - 1
+				off += int64(f.bitFieldWidth)
+				f.promote = integerPromotion(a, f.Type())
+			}
+		default:
+			off = roundup(off, 8)
+			f.offset = uintptr(off) >> 3
+			off += 8 * int64(f.Type().Size())
+			f.promote = integerPromotion(a, f.Type())
+		}
+		prev = f
+	}
+	var lf *field
+	for _, f := range t.fields {
+		if lf != nil && !lf.isBitField && !f.isBitField {
+			lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
+		}
+		lf = f
+	}
+	t.align = byte(align)
+	t.fieldAlign = byte(align)
+	switch {
+	case lf != nil && lf.IsBitField():
+		off = mathutil.MaxInt64(off, int64(lf.Offset()*8)+int64(lf.BitFieldOffset()+8*lf.Type().Align()))
+		off = roundup(off, 8*int64(align))
+	default:
+		off0 := off
+		off = roundup(off, 8*int64(align))
+		if lf != nil && !lf.IsBitField() {
+			lf.pad = byte(off-off0) >> 3
+		}
+	}
+	t.size = uintptr(off >> 3)
+	ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
+	return t
+}