vm: don't call Diagnose when VM hasn't crashed

Fixes #875

1 files changed, 8 insertions, 2 deletions

diff --git a/vm/vm.go b/vm/vm.go
index 26bd21745..b403956a6 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -230,10 +230,13 @@ type monitor struct {
 }
 
 func (mon *monitor) extractError(defaultError string) *report.Report {
+	crashed := defaultError != "" || !mon.canExit
+	if crashed {
+		mon.inst.Diagnose()
+	}
 	// Give it some time to finish writing the error message.
-	mon.inst.Diagnose()
 	mon.waitForOutput()
-	if bytes.Contains(mon.output, []byte(fuzzerPreemptedStr)) {
+	if bytes.Contains(mon.output, []byte("SYZ-FUZZER: PREEMPTED")) {
 		return nil
 	}
 	if !mon.reporter.ContainsCrash(mon.output[mon.matchPos:]) {
@@ -250,6 +253,9 @@ func (mon *monitor) extractError(defaultError string) *report.Report {
 		}
 		return rep
 	}
+	if !crashed && mon.inst.Diagnose() {
+		mon.waitForOutput()
+	}
 	rep := mon.reporter.Parse(mon.output[mon.matchPos:])
 	if rep == nil {
 		panic(fmt.Sprintf("reporter.ContainsCrash/Parse disagree:\n%s", mon.output[mon.matchPos:]))