code review 165780043: runtime: add GODEBUG debugptrs setting

runtime: add GODEBUG invalidptr setting

Fixes issue 8861.
Fixes issue 8911.

[rsc, 2014-10-28 15:19:53]

Hello r (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[r, 2014-10-28 20:42:38]

LGTM

[r, 2014-10-28 20:42:51]

release notes?

[rsc, 2014-10-28 20:55:53]

maybe. the crashes mostly went in in Go 1.3, but there are a few more now
because the
places that used to split the stack didn't check, and now they grow the
stack and do check.
if you want to include some text:

As of Go 1.3, the runtime crashes if it finds a memory word that should
contain
a valid pointer and instead contains an obviously invalid pointer (for
example, the value 1).
Programs that store integers in pointer values may run afoul of this check
and crash.
In Go 1.4, setting the (link to /pkg/runtime docs) GODEBUG variable
invalidptr=0 disables
the crash as a workaround, but we cannot guarantee that future releases
will be
able to avoid the crash; the correct fix is to rewrite code not to alias
integers and pointers.

[rsc, 2014-10-29 01:53:35]

*** Submitted as https://code.google.com/p/go/source/detail?r=7fa57615d950 ***

runtime: add GODEBUG invalidptr setting

Fixes issue 8861.
Fixes issue 8911.

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/165780043