runtime: enable stack scanning by frames

Update #5134

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/9406046

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index f9dbdbb4a111d917b8d71f56ae83bf754f9986a3..b5f81c7e755523314969a3aa7b87942ec8f1a786 100644 (file)
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -18,7 +18,7 @@ enum {
        Debug = 0,
        DebugMark = 0,  // run second pass to check mark
        CollectStats = 0,
-       ScanStackByFrames = 0,
+       ScanStackByFrames = 1,
        IgnorePreciseGC = 0,
 
        // Four bits per word (see #defines below).
@@ -1459,6 +1459,8 @@ addstackroots(G *gp)
                }
        }
        if (ScanStackByFrames) {
+               USED(stk);
+               USED(guard);
                doframe = false;
                runtime·gentraceback(pc, sp, nil, gp, 0, nil, 0x7fffffff, addframeroots, &doframe);
        } else {