[Bug go/66138] New: json decoder Decode function fails for some structure return values

[boger at us dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66138

            Bug ID: 66138
           Summary: json decoder Decode function fails for some structure
                    return values
           Product: gcc
           Version: 5.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: boger at us dot ibm.com
                CC: cmang at google dot com
  Target Milestone: ---
              Host: ppc64le, ppc64, x86_64
            Target: ppc64le, ppc64, x86_64

Created attachment 35538
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35538&action=edit
failing testcase

I'm attaching a testcase that fails when built with gccgo on ppc64le and x86_64
from the gcc5 branch.  The test also fails using gccgo built from gcc trunk on
ppc64le.  The same testcase works if compiled with gc for ppc64le and x86_64.

The problem occurs when creating a json decoder.  The difference in the cases
that pass and fail is the format of the structure being passed to the Decode
function to hold the return value.  The calls to DecodeContainerConfig2
demonstrate structures that work.  The calls to DecodeContainerConfig use
structures that fail with gccgo.

Incorrect output looks like this:

./resconf
HC  &{1000 []}
CONFIG  &{host with memory at top level}
HC  &{1000 [/tmp:/tmp]}
CONFIG  &{host with memory at top level and a hostconfig}
HC  &{1000 [/tmp:/tmp]}
CONFIG  &{host with memory inside hostconfig}


ORIGINAL CODE CAUSE
CONFIG  &{host with memory at top level}
HC  &{0 []}
CONFIG  &{host with memory at top level and a hostconfig}
HC  &{0 []}
CONFIG  &{host with memory inside hostconfig}
HC  &{0 []}

Correct output:

./resconf
HC  &{1000 []}
CONFIG  &{host with memory at top level}
HC  &{1000 [/tmp:/tmp]}
CONFIG  &{host with memory at top level and a hostconfig}
HC  &{1000 [/tmp:/tmp]}
CONFIG  &{host with memory inside hostconfig}


ORIGINAL CODE CAUSE
CONFIG  &{host with memory at top level}
HC  &{1000 []}
CONFIG  &{host with memory at top level and a hostconfig}
HC  &{1000 [/tmp:/tmp]}
CONFIG  &{host with memory inside hostconfig}
HC  &{1000 [/tmp:/tmp]}