runtime: clear Defer.fn before removing from the G.defer list

Should fix the remaining 'invalid heap pointer' build failures.

TBR=khr
CC=golang-codereviews
https://golang.org/cl/152360043

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index 58b14b09e38cd96732e332753df24de88378a0c2..685ff5ca0bcc3aff9c1dd75400c216d336359fac 100644 (file)
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -191,6 +191,9 @@ func freedefer(d *_defer) {
        if d._panic != nil {
                freedeferpanic()
        }
+       if d.fn != nil {
+               freedeferfn()
+       }
        sc := deferclass(uintptr(d.siz))
        if sc < uintptr(len(p{}.deferpool)) {
                mp := acquirem()
@@ -209,6 +212,11 @@ func freedeferpanic() {
        gothrow("freedefer with d._panic != nil")
 }
 
+func freedeferfn() {
+       // fn must be cleared before d is unlinked from gp.
+       gothrow("freedefer with d.fn != nil")
+}
+
 // Run a deferred function if there is one.
 // The compiler inserts a call to this at the end of any
 // function which calls defer.
@@ -241,6 +249,7 @@ func deferreturn(arg0 uintptr) {
        mp := acquirem()
        memmove(unsafe.Pointer(argp), deferArgs(d), uintptr(d.siz))
        fn := d.fn
+       d.fn = nil
        gp._defer = d.link
        freedefer(d)
        releasem(mp)
@@ -270,6 +279,7 @@ func Goexit() {
                                d._panic.aborted = true
                                d._panic = nil
                        }
+                       d.fn = nil
                        gp._defer = d.link
                        freedefer(d)
                        continue
@@ -280,6 +290,7 @@ func Goexit() {
                        gothrow("bad defer entry in Goexit")
                }
                d._panic = nil
+               d.fn = nil
                gp._defer = d.link
                freedefer(d)
                // Note: we ignore recovers here because Goexit isn't a panic
@@ -356,6 +367,7 @@ func gopanic(e interface{}) {
                                d._panic.aborted = true
                        }
                        d._panic = nil
+                       d.fn = nil
                        gp._defer = d.link
                        freedefer(d)
                        continue
@@ -380,6 +392,7 @@ func gopanic(e interface{}) {
                        gothrow("bad defer entry in panic")
                }
                d._panic = nil
+               d.fn = nil
                gp._defer = d.link
 
                // trigger shrinkage to test stack copy.  See stack_test.go:TestStackPanic