RFR (L, tedious again, sorry) 8189610: Reconcile jvm.h and all jvm_md.h between java.base and hotspot

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Fri Oct 27 11:44:53 UTC 2017

On 2017-10-26 22:44, coleen.phillimore at oracle.com wrote:
>  Hi Magnus,
> Thank you for reviewing this.   I have a new version that takes out 
> the hack in globalDefinitions.hpp and adds casts to 
> src/hotspot/share/opto/type.cpp instead.
> Also some fixes from Martin at SAP.
> open webrev at http://cr.openjdk.java.net/~coleenp/8189610.02/webrev
> see below.
> On 10/26/17 5:57 AM, Magnus Ihse Bursie wrote:
>> Coleen,
>> Thank you for addressing this!
>> On 2017-10-25 18:49, coleen.phillimore at oracle.com wrote:
>>> Summary: removed hotspot version of jvm*h and jni*h files
>>> Mostly used sed to remove prims/jvm.h and move #include "jvm.h" 
>>> after precompiled.h, so if you have repetitive stress wrist issues 
>>> don't click on most of these files.
>>> There were more issues to resolve, however.  The JDK windows 
>>> jni_md.h file defined jint as long and the hotspot windows jni_x86.h 
>>> as int.  I had to choose the jdk version since it's the public 
>>> version, so there are changes to the hotspot files for this. 
>>> Generally I changed the code to use 'int' rather than 'jint' where 
>>> the surrounding API didn't insist on consistently using java types. 
>>> We should mostly be using C++ types within hotspot except in 
>>> interfaces to native/JNI code. There are a couple of hacks in places 
>>> where adding multiple jint casts was too painful.
>>> Tested with JPRT and tier2-4 (in progress).
>>> open webrev at http://cr.openjdk.java.net/~coleenp/8189610.01/webrev
>> Looks great!
>> Just a few comments:
>> * src/java.base/unix/native/include/jni_md.h:
>> I don't think the externally_visible attribute should be there for 
>> arm. I know this was the case for the corresponding hotspot file for 
>> arm, but that was techically incorrect. The proper dependency here is 
>> that externally_visible should be in all JNIEXPORT if and only if 
>> we're building with JVM feature "link-time-opt". Traditionally, that 
>> feature been enabled when building arm32 builds, and only then, so 
>> there's been a (coincidentally) connection here. Nowadays, Oracle 
>> does not care about the arm32 builds, and I'm not sure if anyone else 
>> is building them with link-time-opt enabled.
>> It does seem wrong to me to export this behavior in the public 
>> jni_md.h file, though. I think the correct way to solve this, if we 
>> should continue supporting link-time-opt is to make sure this 
>> attribute is set for exported hotspot functions. If it's still 
>> needed, that is. A quick googling seems to indicate that 
>> visibility("default") might be enough in modern gcc's.
>> A third option is to remove the support for link-time-opt entirely, 
>> if it's not really used.
> I didn't know how to change this since we are still building ARM with 
> the jdk10/hs repository, and ARM needed this change.  I could wait 
> until we bring down the jdk10/master changes that remove the ARM build 
> and remove this conditional before I push.  Or we could file an RFE to 
> remove link-time-opt (?) and remove it then?

I'm looking into the link-time-opt issue right now. I think it boils 
down to us using an incorrect flag to gcc when linking, -fwhole-program, 
when -fuse-linker-plugin should have been used. This caused all exported 
symbols to disappear unless they were attributed with 
externally_visible, which makes sense for a program but not a shared 
library. I'm currently trying to verify that -fuse-linker-plugin removes 
the need for the externally_visible attribute when using link-time-opt. 
If it does, I'll open a separate bug to fix that, and if I push that 
first, you can safely delete the externally_visible attributes.


>> * src/java.base/unix/native/include/jvm_md.h and 
>> src/java.base/windows/native/include/jvm_md.h:
>> These files define a public API, and contain non-trivial changes. I 
>> suspect you should file a CSR request. (Even though I realize you're 
>> only matching the header file with the reality.)
> I filed the CSR.   Waiting for the next steps.
> Thanks,
> Coleen
>> /Magnus
>>> bug link https://bugs.openjdk.java.net/browse/JDK-8189610
>>> I have a script to update copyright files on commit.
>>> Thanks to Magnus and ErikJ for the makefile changes.
>>> Thanks,
>>> Coleen

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