[Bug go/64001] New: gccgo: crash on stack splitting

[michael.hudson at canonical dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64001

            Bug ID: 64001
           Summary: gccgo: crash on stack splitting
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: michael.hudson at canonical dot com
                CC: cmang at google dot com

Created attachment 34054
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34054&action=edit
gdb session showing the crash

Hi,

This is probably not going to be a super useful bug report -- I don't have a
small reproducer.

That said: the command "gccgo-go get github.com/lxc/lxd" crashes intermittently
while doing https operations.  I'll attach a gdb session.  What seems to be
going on is that $rsp is getting corrupted (ending up pointing off into the
weeds or unaligned).  It's resisted my attempts to debug it further (for
example, afaict __generic_morestack is always returning sane values).  I don't
know if it's relevant that it's happening during an attempt to capture a stack
track for memory profiling.

It doesn't seem to happen with a mainline GCC build I had lying around from a
few weeks ago, but a little poking fails to find any related fixes so it could
just be down to luck as to when the stack split is triggered.