RFR: 8150426: Wrong cast in metadata_at_put

[Kim Barrett]

> On Feb 22, 2016, at 9:36 PM, David Holmes <david.holmes at oracle.com> wrote:
> On 23/02/2016 11:57 AM, Kim Barrett wrote:
>> Please review this fix of an incorrect cast.
>> 
>> This fix was contributed by Timo Kinnunen.
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8150426
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8150426/webrev/
> 
> Fix seems fine, but have to wonder given:
> 
> 128 #ifdef _LP64
> 129   Metadata* metadata_at(int which) const {
> 130     return (Metadata*)*long_at_addr(which); }
> 131   void metadata_at_put(int which, Metadata* contents) {
> 132     *long_at_addr(which) = (jlong)contents;
> 133   }
> 134 #else
> 
> is Windows setting _LP64 even though it is LLP64? Or are we (incorrectly) forcing _LP64 for all 64-bit builds?

Apparently yes.

Coleen wasted a bunch of time on this very same bug a couple of months
ago, when she used metadata_at and metadata_at_put as a starting point
for something she was working on. I helped her track that down, so I
was already familiar with this problem when Timo reported it.

egrep -r -H --exclude-dir=.hg LP64 | egrep -v "\.(h|c|hpp|cpp|xml):" | grep windows

produces around 15 hits in hotspot/make/windows and common/autoconf,
though I think the autoconf hits don't affect windows, so it's only
those in hotspot that are interesting.

There is only one occurrence of LLP64 in the JDK forest, in a comment here:
./jdk/src/jdk.crypto.pkcs11/share/classes/sun/security/pkcs11/wrapper/PKCS11Constants.java:    // This means it is 0xffffffff in ILP32/LLP64 but 0xffffffffffffffff in LP64.

I have a *very* strong memory (from soon after I started working here)
of seeing a comment or document somewhere that described why we're
building Windows with _LP64, but haven't been able to re-find it. I
know I was surprised at the time.

I also wonder whether this still a problem?
https://bugs.openjdk.java.net/browse/JDK-7000871
_LP64 is not always set up correctly

It looks like, in the current jdk9 forest, _LP64 is only set by the
build system, never by headers. I think there might be a couple more
open bugs related to LP64 that could be closed.