From d1cc83472d611a17513795676d650276f823cafd Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Mon, 3 Oct 2016 16:18:17 -0400 Subject: [PATCH] runtime: debug code to panic when marking a free object This adds debug code enabled in gccheckmark mode that panics if we attempt to mark an unallocated object. This is a common issue with the hybrid barrier when we're manipulating uninitialized memory that contains stale pointers. This also tends to catch bugs that will lead to "sweep increased allocation count" crashes closer to the source of the bug. Change-Id: I443ead3eac6f316a46f50b106078b524cac317f4 Reviewed-on: https://go-review.googlesource.com/31761 Reviewed-by: Rick Hudson --- src/runtime/mgcmark.go | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go index e47072d88c..e62e470217 100644 --- a/src/runtime/mgcmark.go +++ b/src/runtime/mgcmark.go @@ -1294,6 +1294,13 @@ func greyobject(obj, base, off uintptr, hbits heapBits, span *mspan, gcw *gcWork throw("setCheckmarked and isCheckmarked disagree") } } else { + if debug.gccheckmark > 0 && span.isFree(objIndex) { + print("runtime: marking free object ", hex(obj), " found at *(", hex(base), "+", hex(off), ")\n") + gcDumpObject("base", base, off) + gcDumpObject("obj", obj, ^uintptr(0)) + throw("marking free object") + } + // If marked we have nothing to do. if mbits.isMarked() { return -- 2.48.1