runtime: diagnose invalid pointers during GC

For #9880. Let's see what breaks.

Change-Id: Ic8b99a604e60177a448af5f7173595feed607875
Reviewed-on: https://go-review.googlesource.com/10818
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>

diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index ef17409ebeb73cc57a4161eacae415cd462853f2..b9b52a7bc416f8974a465534a9b9fa2579d0033c 100644 (file)
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -201,7 +201,7 @@ func heapBitsForObject(p uintptr) (base uintptr, hbits heapBits, s *mspan) {
                // The following ensures that we are rigorous about what data
                // structures hold valid pointers.
                // TODO(rsc): Check if this still happens.
-               if false {
+               if true {
                        // Still happens sometimes. We don't know why.
                        printlock()
                        print("runtime:objectstart Span weird: p=", hex(p), " k=", hex(k))