Update debugger to use Abort interface

R=rsc
APPROVED=rsc
DELTA=314  (132 added, 2 deleted, 180 changed)
OCL=34376
CL=34396

usr/austin/ogle/abort.go

+// 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 ogle
+
+import (
+	"os";
+	"runtime";
+)
+
+// An aborter aborts the thread's current compututation, usually
+// passing the error to a waiting thread.
+type aborter interface {
+	Abort(err os.Error);
+}
+
+type ogleAborter chan os.Error;
+
+func (a ogleAborter) Abort(err os.Error) {
+	a <- err;
+	runtime.Goexit();
+}
+
+// try executes a computation; if the computation Aborts, try returns
+// the error passed to abort.
+func try(f func(a aborter)) os.Error {
+	a := make(ogleAborter);
+	go func() {
+		f(a);
+		a <- nil;
+	}();
+	err := <-a;
+	return err;
+}

usr/austin/ogle/frame.go

@@ -6,6 +6,7 @@ package ogle
 
 import (
 	"fmt";
+	"os";
 	"ptrace";
 	"sym";
 )
@@ -29,14 +30,19 @@ type Frame struct {
 	inner, outer *Frame;
 }
 
-// NewFrame returns the top-most Frame of the given g's thread.
-// This function can abort.
-func NewFrame(g remoteStruct) *Frame {
+// newFrame returns the top-most Frame of the given g's thread.
+func newFrame(g remoteStruct) (*Frame, os.Error) {
+	var f *Frame;
+	err := try(func(a aborter) { f = aNewFrame(a, g) });
+	return f, err;
+}
+
+func aNewFrame(a aborter, g remoteStruct) *Frame {
 	p := g.r.p;
 	var pc, sp ptrace.Word;
 
 	// Is this G alive?
-	switch g.Field(p.f.G.Status).(remoteInt).Get() {
+	switch g.field(p.f.G.Status).(remoteInt).aGet(a) {
 	case p.runtime.Gidle, p.runtime.Gmoribund, p.runtime.Gdead:
 		return nil;
 	}
@@ -61,7 +67,7 @@ func NewFrame(g remoteStruct) *Frame {
 
 			// If this thread crashed, try to recover it
 			if pc == 0 {
-				pc = p.peekUintptr(pc);
+				pc = p.peekUintptr(a, pc);
 				sp += 8;
 			}
 
@@ -72,22 +78,21 @@ func NewFrame(g remoteStruct) *Frame {
 	if pc == 0 && sp == 0 {
 		// G is not mapped to an OS thread.  Use the
 		// scheduler's stored PC and SP.
-		sched := g.Field(p.f.G.Sched).(remoteStruct);
-		pc = ptrace.Word(sched.Field(p.f.Gobuf.Pc).(remoteUint).Get());
-		sp = ptrace.Word(sched.Field(p.f.Gobuf.Sp).(remoteUint).Get());
+		sched := g.field(p.f.G.Sched).(remoteStruct);
+		pc = ptrace.Word(sched.field(p.f.Gobuf.Pc).(remoteUint).aGet(a));
+		sp = ptrace.Word(sched.field(p.f.Gobuf.Sp).(remoteUint).aGet(a));
 	}
 
 	// Get Stktop
-	stk := g.Field(p.f.G.Stackbase).(remotePtr).Get().(remoteStruct);
+	stk := g.field(p.f.G.Stackbase).(remotePtr).aGet(a).(remoteStruct);
 
-	return prepareFrame(pc, sp, stk, nil);
+	return prepareFrame(a, pc, sp, stk, nil);
 }
 
 // prepareFrame creates a Frame from the PC and SP within that frame,
 // as well as the active stack segment.  This function takes care of
-// traversing stack breaks and unwinding closures.  This function can
-// abort.
-func prepareFrame(pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
+// traversing stack breaks and unwinding closures.
+func prepareFrame(a aborter, pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
 	// Based on src/pkg/runtime/amd64/traceback.c:traceback
 	p := stk.r.p;
 	top := inner == nil;
@@ -101,11 +106,11 @@ func prepareFrame(pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
 		// Traverse segmented stack breaks
 		if p.sys.lessstack != nil && pc == ptrace.Word(p.sys.lessstack.Value) {
 			// Get stk->gobuf.pc
-			pc = ptrace.Word(stk.Field(p.f.Stktop.Gobuf).(remoteStruct).Field(p.f.Gobuf.Pc).(remoteUint).Get());
+			pc = ptrace.Word(stk.field(p.f.Stktop.Gobuf).(remoteStruct).field(p.f.Gobuf.Pc).(remoteUint).aGet(a));
 			// Get stk->gobuf.sp
-			sp = ptrace.Word(stk.Field(p.f.Stktop.Gobuf).(remoteStruct).Field(p.f.Gobuf.Sp).(remoteUint).Get());
+			sp = ptrace.Word(stk.field(p.f.Stktop.Gobuf).(remoteStruct).field(p.f.Gobuf.Sp).(remoteUint).aGet(a));
 			// Get stk->stackbase
-			stk = stk.Field(p.f.Stktop.Stackbase).(remotePtr).Get().(remoteStruct);
+			stk = stk.field(p.f.Stktop.Stackbase).(remotePtr).aGet(a).(remoteStruct);
 			continue;
 		}
 
@@ -129,7 +134,7 @@ func prepareFrame(pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
 		spdelta, ok := p.ParseClosure(buf);
 		if ok {
 			sp += ptrace.Word(spdelta);
-			pc = p.peekUintptr(sp - ptrace.Word(p.PtrSize()));
+			pc = p.peekUintptr(a, sp - ptrace.Word(p.PtrSize()));
 		}
 	}
 	if fn == nil {
@@ -159,8 +164,14 @@ func prepareFrame(pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
 }
 
 // Outer returns the Frame that called this Frame, or nil if this is
-// the outermost frame.  This function can abort.
-func (f *Frame) Outer() *Frame {
+// the outermost frame.
+func (f *Frame) Outer() (*Frame, os.Error) {
+	var fr *Frame;
+	err := try(func(a aborter) { fr = f.aOuter(a) });
+	return fr, err;
+}
+
+func (f *Frame) aOuter(a aborter) *Frame {
 	// Is there a cached outer frame
 	if f.outer != nil {
 		return f.outer;
@@ -177,14 +188,14 @@ func (f *Frame) Outer() *Frame {
 		sp += ptrace.Word(2 * p.PtrSize());
 	}
 
-	pc := p.peekUintptr(f.fp - ptrace.Word(p.PtrSize()));
+	pc := p.peekUintptr(a, f.fp - ptrace.Word(p.PtrSize()));
 	if pc < 0x1000 {
 		return nil;
 	}
 
 	// TODO(austin) Register this frame for shoot-down.
 
-	f.outer = prepareFrame(pc, sp, f.stk, f);
+	f.outer = prepareFrame(a, pc, sp, f.stk, f);
 	return f.outer;
 }
 

usr/austin/ogle/goroutine.go

@@ -5,6 +5,7 @@
 package ogle
 
 import (
+	"eval";
 	"fmt";
 	"os";
 	"ptrace";
@@ -31,21 +32,21 @@ func (t *Goroutine) isG0() bool {
 	return t.g.addr().base == t.g.r.p.sys.g0.addr().base;
 }
 
-func (t *Goroutine) resetFrame() {
-	// TODO(austin) NewFrame can abort
+func (t *Goroutine) resetFrame() (err os.Error) {
 	// TODO(austin) Reuse any live part of the current frame stack
 	// so existing references to Frame's keep working.
-	t.frame = NewFrame(t.g);
+	t.frame, err = newFrame(t.g);
+	return;
 }
 
 // Out selects the caller frame of the current frame.
 func (t *Goroutine) Out() os.Error {
 	// TODO(austin) Outer can abort
-	f := t.frame.Outer();
+	f, err := t.frame.Outer();
 	if f != nil {
 		t.frame = f;
 	}
-	return nil;
+	return err;
 }
 
 // In selects the frame called by the current frame.
@@ -70,7 +71,11 @@ func readylockedBP(ev Event) (EventAction, os.Error) {
 	sp := regs.SP();
 	addr := sp + ptrace.Word(p.PtrSize());
 	arg := remotePtr{remote{addr, p}, p.runtime.G};
-	gp := arg.Get();
+	var gp eval.Value;
+	err = try(func(a aborter) { gp = arg.aGet(a) });
+	if err != nil {
+		return EAStop, err;
+	}
 	if gp == nil {
 		return EAStop, UnknownGoroutine{b.osThread, 0};
 	}

usr/austin/ogle/process.go

@@ -137,12 +137,17 @@ func NewProcess(proc ptrace.Process, arch Arch, syms *sym.GoSymTable) (*Process,
 
 	// Get current goroutines
 	p.goroutines[p.sys.g0.addr().base] = &Goroutine{p.sys.g0, nil, false};
-	g := p.sys.allg.Get();
+	err := try(func(a aborter) {
+		g := p.sys.allg.aGet(a);
 		for g != nil {
 			gs := g.(remoteStruct);
 			fmt.Printf("*** Found goroutine at %#x\n", gs.addr().base);
 			p.goroutines[gs.addr().base] = &Goroutine{gs, nil, false};
-		g = gs.Field(p.f.G.Alllink).(remotePtr).Get();
+			g = gs.field(p.f.G.Alllink).(remotePtr).aGet(a);
+		}
+	});
+	if err != nil {
+		return nil, err;
 	}
 	p.selectSomeGoroutine();
 
@@ -282,8 +287,8 @@ func (p *Process) Poke(addr ptrace.Word, b []byte) (int, os.Error) {
 	return thr.Poke(addr, b);
 }
 
-func (p *Process) peekUintptr(addr ptrace.Word) ptrace.Word {
-	return ptrace.Word(mkUintptr(remote{addr, p}).(remoteUint).Get());
+func (p *Process) peekUintptr(a aborter, addr ptrace.Word) ptrace.Word {
+	return ptrace.Word(mkUintptr(remote{addr, p}).(remoteUint).aGet(a));
 }
 
 /*

usr/austin/ogle/rtype.go

@@ -122,7 +122,7 @@ var prtIndent = "";
 
 // parseRemoteType parses a Type structure in a remote process to
 // construct the corresponding interpreter type and remote type.
-func parseRemoteType(rs remoteStruct) *remoteType {
+func parseRemoteType(a aborter, rs remoteStruct) *remoteType {
 	addr := rs.addr().base;
 	p := rs.addr().p;
 
@@ -156,17 +156,17 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	}
 
 	// Get Type header
-	itype := ptrace.Word(rs.Field(p.f.Type.Typ).(remoteUint).Get());
-	typ := rs.Field(p.f.Type.Ptr).(remotePtr).Get().(remoteStruct);
+	itype := ptrace.Word(rs.field(p.f.Type.Typ).(remoteUint).aGet(a));
+	typ := rs.field(p.f.Type.Ptr).(remotePtr).aGet(a).(remoteStruct);
 
 	// Is this a named type?
 	var nt *eval.NamedType;
-	uncommon := typ.Field(p.f.CommonType.UncommonType).(remotePtr).Get();
+	uncommon := typ.field(p.f.CommonType.UncommonType).(remotePtr).aGet(a);
 	if uncommon != nil {
-		name := uncommon.(remoteStruct).Field(p.f.UncommonType.Name).(remotePtr).Get();
+		name := uncommon.(remoteStruct).field(p.f.UncommonType.Name).(remotePtr).aGet(a);
 		if name != nil {
 			// TODO(austin) Declare type in appropriate remote package
-			nt = eval.NewNamedType(name.(remoteString).Get());
+			nt = eval.NewNamedType(name.(remoteString).aGet(a));
 			rt.Type = nt;
 		}
 	}
@@ -227,8 +227,8 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	case p.runtime.PArrayType:
 		// Cast to an ArrayType
 		typ := p.runtime.ArrayType.mk(typ.addr()).(remoteStruct);
-		len := int64(typ.Field(p.f.ArrayType.Len).(remoteUint).Get());
-		elem := parseRemoteType(typ.Field(p.f.ArrayType.Elem).(remotePtr).Get().(remoteStruct));
+		len := int64(typ.field(p.f.ArrayType.Len).(remoteUint).aGet(a));
+		elem := parseRemoteType(a, typ.field(p.f.ArrayType.Elem).(remotePtr).aGet(a).(remoteStruct));
 		t = eval.NewArrayType(len, elem.Type);
 		mk = func(r remote) eval.Value {
 			return remoteArray{r, len, elem};
@@ -237,22 +237,22 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	case p.runtime.PStructType:
 		// Cast to a StructType
 		typ := p.runtime.StructType.mk(typ.addr()).(remoteStruct);
-		fs := typ.Field(p.f.StructType.Fields).(remoteSlice).Get();
+		fs := typ.field(p.f.StructType.Fields).(remoteSlice).aGet(a);
 
 		fields := make([]eval.StructField, fs.Len);
 		layout := make([]remoteStructField, fs.Len);
 		for i := range fields {
-			f := fs.Base.Elem(int64(i)).(remoteStruct);
-			elemrs := f.Field(p.f.StructField.Typ).(remotePtr).Get().(remoteStruct);
-			elem := parseRemoteType(elemrs);
+			f := fs.Base.(remoteArray).elem(int64(i)).(remoteStruct);
+			elemrs := f.field(p.f.StructField.Typ).(remotePtr).aGet(a).(remoteStruct);
+			elem := parseRemoteType(a, elemrs);
 			fields[i].Type = elem.Type;
-			name := f.Field(p.f.StructField.Name).(remotePtr).Get();
+			name := f.field(p.f.StructField.Name).(remotePtr).aGet(a);
 			if name == nil {
 				fields[i].Anonymous = true;
 			} else {
-				fields[i].Name = name.(remoteString).Get();
+				fields[i].Name = name.(remoteString).aGet(a);
 			}
-			layout[i].offset = int(f.Field(p.f.StructField.Offset).(remoteUint).Get());
+			layout[i].offset = int(f.field(p.f.StructField.Offset).(remoteUint).aGet(a));
 			layout[i].fieldType = elem;
 		}
 
@@ -264,7 +264,7 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	case p.runtime.PPtrType:
 		// Cast to a PtrType
 		typ := p.runtime.PtrType.mk(typ.addr()).(remoteStruct);
-		elem := parseRemoteType(typ.Field(p.f.PtrType.Elem).(remotePtr).Get().(remoteStruct));
+		elem := parseRemoteType(a, typ.field(p.f.PtrType.Elem).(remotePtr).aGet(a).(remoteStruct));
 		t = eval.NewPtrType(elem.Type);
 		mk = func(r remote) eval.Value {
 			return remotePtr{r, elem};
@@ -273,7 +273,7 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	case p.runtime.PSliceType:
 		// Cast to a SliceType
 		typ := p.runtime.SliceType.mk(typ.addr()).(remoteStruct);
-		elem := parseRemoteType(typ.Field(p.f.SliceType.Elem).(remotePtr).Get().(remoteStruct));
+		elem := parseRemoteType(a, typ.field(p.f.SliceType.Elem).(remotePtr).aGet(a).(remoteStruct));
 		t = eval.NewSliceType(elem.Type);
 		mk = func(r remote) eval.Value {
 			return remoteSlice{r, elem};
@@ -291,7 +291,7 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 			name = sym.Common().Name;
 		}
 		err := fmt.Sprintf("runtime type at %#x has unexpected type %#x (%s)", addr, itype, name);
-		eval.Abort(FormatError(err));
+		a.Abort(FormatError(err));
 	}
 
 	// Fill in the remote type
@@ -300,7 +300,7 @@ func parseRemoteType(rs remoteStruct) *remoteType {
 	} else {
 		rt.Type = t;
 	}
-	rt.size = int(typ.Field(p.f.CommonType.Size).(remoteUint).Get());
+	rt.size = int(typ.field(p.f.CommonType.Size).(remoteUint).aGet(a));
 	rt.mk = mk;
 
 	return rt;

usr/austin/ogle/rvalue.go

@@ -7,6 +7,7 @@ package ogle
 import (
 	"eval";
 	"fmt";
+	"os";
 	"ptrace";
 )
 
@@ -34,7 +35,7 @@ type remote struct {
 	p *Process;
 }
 
-func (v remote) Get(size int) uint64 {
+func (v remote) Get(a aborter, size int) uint64 {
 	// TODO(austin) This variable might temporarily be in a
 	// register.  We could trace the assembly back from the
 	// current PC, looking for the beginning of the function or a
@@ -55,18 +56,18 @@ func (v remote) Get(size int) uint64 {
 	buf := arr[0:size];
 	_, err := v.p.Peek(v.base, buf);
 	if err != nil {
-		eval.Abort(err);
+		a.Abort(err);
 	}
 	return uint64(v.p.ToWord(buf));
 }
 
-func (v remote) Set(size int, x uint64) {
+func (v remote) Set(a aborter, size int, x uint64) {
 	var arr [8]byte;
 	buf := arr[0:size];
 	v.p.FromWord(ptrace.Word(x), buf);
 	_, err := v.p.Poke(v.base, buf);
 	if err != nil {
-		eval.Abort(err);
+		a.Abort(err);
 	}
 }
 
@@ -74,6 +75,15 @@ func (v remote) plus(x ptrace.Word) remote {
 	return remote{v.base + x, v.p};
 }
 
+func tryRVString(f func(a aborter) string) string {
+	var s string;
+	err := try(func(a aborter) { s = f(a) });
+	if err != nil {
+		return fmt.Sprintf("<error: %v>", err);
+	}
+	return s;
+}
+
 /*
  * Bool
  */
@@ -83,22 +93,30 @@ type remoteBool struct {
 }
 
 func (v remoteBool) String() string {
-	return fmt.Sprintf("%v", v.Get());
+	return tryRVString(func(a aborter) string { return fmt.Sprintf("%v", v.aGet(a)) });
 }
 
-func (v remoteBool) Assign(o eval.Value) {
-	v.Set(o.(eval.BoolValue).Get());
+func (v remoteBool) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.BoolValue).Get(t));
 }
 
-func (v remoteBool) Get() bool {
-	return v.r.Get(1) != 0;
+func (v remoteBool) Get(t *eval.Thread) bool {
+	return v.aGet(t);
 }
 
-func (v remoteBool) Set(x bool) {
+func (v remoteBool) aGet(a aborter) bool {
+	return v.r.Get(a, 1) != 0;
+}
+
+func (v remoteBool) Set(t *eval.Thread, x bool) {
+	v.aSet(t, x);
+}
+
+func (v remoteBool) aSet(a aborter, x bool) {
 	if x {
-		v.r.Set(1, 1);
+		v.r.Set(a, 1, 1);
 	} else {
-		v.r.Set(1, 0);
+		v.r.Set(a, 1, 0);
 	}
 }
 
@@ -120,19 +138,27 @@ type remoteUint struct {
 }
 
 func (v remoteUint) String() string {
-	return fmt.Sprintf("%v", v.Get());
+	return tryRVString(func(a aborter) string { return fmt.Sprintf("%v", v.aGet(a)) });
+}
+
+func (v remoteUint) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.UintValue).Get(t));
+}
+
+func (v remoteUint) Get(t *eval.Thread) uint64 {
+	return v.aGet(t);
 }
 
-func (v remoteUint) Assign(o eval.Value) {
-	v.Set(o.(eval.UintValue).Get());
+func (v remoteUint) aGet(a aborter) uint64 {
+	return v.r.Get(a, v.size);
 }
 
-func (v remoteUint) Get() uint64 {
-	return v.r.Get(v.size);
+func (v remoteUint) Set(t *eval.Thread, x uint64) {
+	v.aSet(t, x);
 }
 
-func (v remoteUint) Set(x uint64) {
-	v.r.Set(v.size, x);
+func (v remoteUint) aSet(a aborter, x uint64) {
+	v.r.Set(a, v.size, x);
 }
 
 func (v remoteUint) addr() remote {
@@ -173,19 +199,27 @@ type remoteInt struct {
 }
 
 func (v remoteInt) String() string {
-	return fmt.Sprintf("%v", v.Get());
+	return tryRVString(func(a aborter) string { return fmt.Sprintf("%v", v.aGet(a)) });
+}
+
+func (v remoteInt) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.IntValue).Get(t));
 }
 
-func (v remoteInt) Assign(o eval.Value) {
-	v.Set(o.(eval.IntValue).Get());
+func (v remoteInt) Get(t *eval.Thread) int64 {
+	return v.aGet(t);
 }
 
-func (v remoteInt) Get() int64 {
-	return int64(v.r.Get(v.size));
+func (v remoteInt) aGet(a aborter) int64 {
+	return int64(v.r.Get(a, v.size));
 }
 
-func (v remoteInt) Set(x int64) {
-	v.r.Set(v.size, uint64(x));
+func (v remoteInt) Set(t *eval.Thread, x int64) {
+	v.aSet(t, x);
+}
+
+func (v remoteInt) aSet(a aborter, x int64) {
+	v.r.Set(a, v.size, uint64(x));
 }
 
 func (v remoteInt) addr() remote {
@@ -222,15 +256,19 @@ type remoteFloat struct {
 }
 
 func (v remoteFloat) String() string {
-	return fmt.Sprintf("%v", v.Get());
+	return tryRVString(func(a aborter) string { return fmt.Sprintf("%v", v.aGet(a)) });
+}
+
+func (v remoteFloat) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.FloatValue).Get(t));
 }
 
-func (v remoteFloat) Assign(o eval.Value) {
-	v.Set(o.(eval.FloatValue).Get());
+func (v remoteFloat) Get(t *eval.Thread) float64 {
+	return v.aGet(t);
 }
 
-func (v remoteFloat) Get() float64 {
-	bits := v.r.Get(v.size);
+func (v remoteFloat) aGet(a aborter) float64 {
+	bits := v.r.Get(a, v.size);
 	switch v.size {
 	case 4:
 		return float64(v.r.p.ToFloat32(uint32(bits)));
@@ -240,7 +278,11 @@ func (v remoteFloat) Get() float64 {
 	panic("Unexpected float size ", v.size);
 }
 
-func (v remoteFloat) Set(x float64) {
+func (v remoteFloat) Set(t *eval.Thread, x float64) {
+	v.aSet(t, x);
+}
+
+func (v remoteFloat) aSet(a aborter, x float64) {
 	var bits uint64;
 	switch v.size{
 	case 4:
@@ -250,7 +292,7 @@ func (v remoteFloat) Set(x float64) {
 	default:
 		panic("Unexpected float size ", v.size);
 	}
-	v.r.Set(v.size, bits);
+	v.r.Set(a, v.size, bits);
 }
 
 func (v remoteFloat) addr() remote {
@@ -278,30 +320,38 @@ type remoteString struct {
 }
 
 func (v remoteString) String() string {
-	return v.Get();
+	return tryRVString(func(a aborter) string { return v.aGet(a) });
 }
 
-func (v remoteString) Assign(o eval.Value) {
-	v.Set(o.(eval.StringValue).Get());
+func (v remoteString) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.StringValue).Get(t));
 }
 
-func (v remoteString) Get() string {
+func (v remoteString) Get(t *eval.Thread) string {
+	return v.aGet(t);
+}
+
+func (v remoteString) aGet(a aborter) string {
 	rs := v.r.p.runtime.String.mk(v.r).(remoteStruct);
-	str := ptrace.Word(rs.Field(v.r.p.f.String.Str).(remoteUint).Get());
-	len := rs.Field(v.r.p.f.String.Len).(remoteInt).Get();
+	str := ptrace.Word(rs.field(v.r.p.f.String.Str).(remoteUint).aGet(a));
+	len := rs.field(v.r.p.f.String.Len).(remoteInt).aGet(a);
 	
 	bytes := make([]uint8, len);
 	_, err := v.r.p.Peek(str, bytes);
 	if err != nil {
-		eval.Abort(err);
+		a.Abort(err);
 	}
 	return string(bytes);
 }
 
-func (v remoteString) Set(x string) {
+func (v remoteString) Set(t *eval.Thread, x string) {
+	v.aSet(t, x);
+}
+
+func (v remoteString) aSet(a aborter, x string) {
 	// TODO(austin) This isn't generally possible without the
 	// ability to allocate remote memory.
-	eval.Abort(RemoteMismatchError("remote strings cannot be assigned to"));
+	a.Abort(RemoteMismatchError("remote strings cannot be assigned to"));
 }
 
 func mkString(r remote) eval.Value {
@@ -324,30 +374,34 @@ func (v remoteArray) String() string {
 		if i > 0 {
 			res += ", ";
 		}
-		res += v.Elem(i).String();
+		res += v.elem(i).String();
 	}
 	return res + "}";
 }
 
-func (v remoteArray) Assign(o eval.Value) {
+func (v remoteArray) Assign(t *eval.Thread, o eval.Value) {
  	// TODO(austin) Could do a bigger memcpy if o is a
 	// remoteArray in the same Process.
 	oa := o.(eval.ArrayValue);
 	for i := int64(0); i < v.len; i++ {
-		v.Elem(i).Assign(oa.Elem(i));
+		v.Elem(t, i).Assign(t, oa.Elem(t, i));
 	}
 }
 
-func (v remoteArray) Get() eval.ArrayValue {
+func (v remoteArray) Get(t *eval.Thread) eval.ArrayValue {
 	return v;
 }
 
-func (v remoteArray) Elem(i int64) eval.Value {
+func (v remoteArray) Elem(t *eval.Thread, i int64) eval.Value {
+	return v.elem(i);
+}
+
+func (v remoteArray) elem(i int64) eval.Value {
 	return v.elemType.mk(v.r.plus(ptrace.Word(int64(v.elemType.size) * i)));
 }
 
-func (v remoteArray) From(i int64) eval.ArrayValue {
-	return remoteArray{v.r.plus(ptrace.Word(int64(v.elemType.size) * i)), v.len - i, v.elemType};
+func (v remoteArray) Sub(i int64, len int64) eval.ArrayValue {
+	return remoteArray{v.r.plus(ptrace.Word(int64(v.elemType.size) * i)), len, v.elemType};
 }
 
 /*
@@ -370,25 +424,29 @@ func (v remoteStruct) String() string {
 		if i > 0 {
 			res += ", ";
 		}
-		res += v.Field(i).String();
+		res += v.field(i).String();
 	}
 	return res + "}";
 }
 
-func (v remoteStruct) Assign(o eval.Value) {
+func (v remoteStruct) Assign(t *eval.Thread, o eval.Value) {
 	// TODO(austin) Could do a bigger memcpy.
 	oa := o.(eval.StructValue);
 	l := len(v.layout);
 	for i := 0; i < l; i++ {
-		v.Field(i).Assign(oa.Field(i));
+		v.Field(t, i).Assign(t, oa.Field(t, i));
 	}
 }
 
-func (v remoteStruct) Get() eval.StructValue {
+func (v remoteStruct) Get(t *eval.Thread) eval.StructValue {
 	return v;
 }
 
-func (v remoteStruct) Field(i int) eval.Value {
+func (v remoteStruct) Field(t *eval.Thread, i int) eval.Value {
+	return v.field(i);
+}
+
+func (v remoteStruct) field(i int) eval.Value {
 	f := &v.layout[i];
 	return f.fieldType.mk(v.r.plus(ptrace.Word(f.offset)));
 }
@@ -411,35 +469,45 @@ type remotePtr struct {
 }
 
 func (v remotePtr) String() string {
-	e := v.Get();
+	return tryRVString(func(a aborter) string {
+		e := v.aGet(a);
 		if e == nil {
 			return "<nil>";
 		}
 		return "&" + e.String();
+	});
+}
+
+func (v remotePtr) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.PtrValue).Get(t));
 }
 
-func (v remotePtr) Assign(o eval.Value) {
-	v.Set(o.(eval.PtrValue).Get());
+func (v remotePtr) Get(t *eval.Thread) eval.Value {
+	return v.aGet(t);
 }
 
-func (v remotePtr) Get() eval.Value {
-	addr := ptrace.Word(v.r.Get(v.r.p.PtrSize()));
+func (v remotePtr) aGet(a aborter) eval.Value {
+	addr := ptrace.Word(v.r.Get(a, v.r.p.PtrSize()));
 	if addr == 0 {
 		return nil;
 	}
 	return v.elemType.mk(remote{addr, v.r.p});
 }
 
-func (v remotePtr) Set(x eval.Value) {
+func (v remotePtr) Set(t *eval.Thread, x eval.Value) {
+	v.aSet(t, x);
+}
+
+func (v remotePtr) aSet(a aborter, x eval.Value) {
 	if x == nil {
-		v.r.Set(v.r.p.PtrSize(), 0);
+		v.r.Set(a, v.r.p.PtrSize(), 0);
 		return;
 	}
 	xr, ok := x.(remoteValue);
 	if !ok || v.r.p != xr.addr().p {
-		eval.Abort(RemoteMismatchError("remote pointer must point within the same process"));
+		a.Abort(RemoteMismatchError("remote pointer must point within the same process"));
 	}
-	v.r.Set(v.r.p.PtrSize(), uint64(xr.addr().base));
+	v.r.Set(a, v.r.p.PtrSize(), uint64(xr.addr().base));
 }
 
 func (v remotePtr) addr() remote {
@@ -456,39 +524,49 @@ type remoteSlice struct {
 }
 
 func (v remoteSlice) String() string {
-	b := v.Get().Base;
+	return tryRVString(func(a aborter) string {
+		b := v.aGet(a).Base;
 		if b == nil {
 			return "<nil>";
 		}
 		return b.String();
+	});
 }
 
-func (v remoteSlice) Assign(o eval.Value) {
-	v.Set(o.(eval.SliceValue).Get());
+func (v remoteSlice) Assign(t *eval.Thread, o eval.Value) {
+	v.Set(t, o.(eval.SliceValue).Get(t));
 }
 
-func (v remoteSlice) Get() eval.Slice {
+func (v remoteSlice) Get(t *eval.Thread) eval.Slice {
+	return v.aGet(t);
+}
+
+func (v remoteSlice) aGet(a aborter) eval.Slice {
 	rs := v.r.p.runtime.Slice.mk(v.r).(remoteStruct);
-	base := ptrace.Word(rs.Field(v.r.p.f.Slice.Array).(remoteUint).Get());
-	nel := rs.Field(v.r.p.f.Slice.Len).(remoteInt).Get();
-	cap := rs.Field(v.r.p.f.Slice.Cap).(remoteInt).Get();
+	base := ptrace.Word(rs.field(v.r.p.f.Slice.Array).(remoteUint).aGet(a));
+	nel := rs.field(v.r.p.f.Slice.Len).(remoteInt).aGet(a);
+	cap := rs.field(v.r.p.f.Slice.Cap).(remoteInt).aGet(a);
 	if base == 0 {
 		return eval.Slice{nil, nel, cap};
 	}
 	return eval.Slice{remoteArray{remote{base, v.r.p}, nel, v.elemType}, nel, cap};
 }
 
-func (v remoteSlice) Set(x eval.Slice) {
+func (v remoteSlice) Set(t *eval.Thread, x eval.Slice) {
+	v.aSet(t, x);
+}
+
+func (v remoteSlice) aSet(a aborter, x eval.Slice) {
 	rs := v.r.p.runtime.Slice.mk(v.r).(remoteStruct);
 	if x.Base == nil {
-		rs.Field(v.r.p.f.Slice.Array).(remoteUint).Set(0);
+		rs.field(v.r.p.f.Slice.Array).(remoteUint).aSet(a, 0);
 	} else {
 		ar, ok := x.Base.(remoteArray);
 		if !ok || v.r.p != ar.r.p {
-			eval.Abort(RemoteMismatchError("remote slice must point within the same process"));
+			a.Abort(RemoteMismatchError("remote slice must point within the same process"));
 		}
-		rs.Field(v.r.p.f.Slice.Array).(remoteUint).Set(uint64(ar.r.base));
+		rs.field(v.r.p.f.Slice.Array).(remoteUint).aSet(a, uint64(ar.r.base));
 	}
-	rs.Field(v.r.p.f.Slice.Len).(remoteInt).Set(x.Len);
-	rs.Field(v.r.p.f.Slice.Cap).(remoteInt).Set(x.Cap);
+	rs.field(v.r.p.f.Slice.Len).(remoteInt).aSet(a, x.Len);
+	rs.field(v.r.p.f.Slice.Cap).(remoteInt).aSet(a, x.Cap);
 }