cmd/internal/obj, cmd/trace: restore bounds checks dropped in CL 56950

CL 56950 correctly identified code with checks that were impossible.
But instead of correcting the checks it deleted them.
This CL corrects the code to check what was meant.

Change-Id: Ic89222184ee4fa5cacccae12d750601a9438ac8d
Reviewed-on: https://go-review.googlesource.com/78113
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/obj/sym.go

@@ -34,6 +34,7 @@ package obj
 import (
 	"cmd/internal/objabi"
 	"fmt"
+	"log"
 	"math"
 )
 
@@ -44,7 +45,9 @@ func Linknew(arch *LinkArch) *Link {
 	ctxt.Arch = arch
 	ctxt.Pathname = objabi.WorkingDir()
 
-	ctxt.Headtype.Set(objabi.GOOS)
+	if err := ctxt.Headtype.Set(objabi.GOOS); err != nil {
+		log.Fatalf("unknown goos %s", objabi.GOOS)
+	}
 
 	ctxt.Flag_optimize = true
 	ctxt.Framepointer_enabled = objabi.Framepointer_enabled(objabi.GOOS, arch.Name)

src/cmd/trace/trace.go

@@ -278,7 +278,7 @@ type traceContext struct {
 
 	heapStats, prevHeapStats     heapStats
 	threadStats, prevThreadStats threadStats
-	gstates, prevGstates         [gStateCount]uint64
+	gstates, prevGstates         [gStateCount]int64
 }
 
 type heapStats struct {
@@ -449,6 +449,9 @@ func generateTrace(params *traceParams) (ViewerData, error) {
 		if setGStateErr != nil {
 			return ctx.data, setGStateErr
 		}
+		if ctx.gstates[gRunnable] < 0 || ctx.gstates[gRunning] < 0 || ctx.threadStats.insyscall < 0 {
+			return ctx.data, fmt.Errorf("invalid state after processing %v: runnable=%d running=%d insyscall=%d", ev, ctx.gstates[gRunnable], ctx.gstates[gRunning], ctx.threadStats.insyscall)
+		}
 
 		// Ignore events that are from uninteresting goroutines
 		// or outside of the interesting timeframe.
@@ -644,7 +647,7 @@ func (ctx *traceContext) emitGoroutineCounters(ev *trace.Event) {
 	if ctx.prevGstates == ctx.gstates {
 		return
 	}
-	ctx.emit(&ViewerEvent{Name: "Goroutines", Phase: "C", Time: ctx.time(ev), Pid: 1, Arg: &goroutineCountersArg{ctx.gstates[gRunning], ctx.gstates[gRunnable], ctx.gstates[gWaitingGC]}})
+	ctx.emit(&ViewerEvent{Name: "Goroutines", Phase: "C", Time: ctx.time(ev), Pid: 1, Arg: &goroutineCountersArg{uint64(ctx.gstates[gRunning]), uint64(ctx.gstates[gRunnable]), uint64(ctx.gstates[gWaitingGC])}})
 	ctx.prevGstates = ctx.gstates
 }