Hi Thomas,
There are not issues caused by this, as you state, the compile forces the
callee and caller back to the same convention.
The only issue we had was with the amount of warning that were produced
when we (IBM) compiled the jdk.
We avoided the error by adding -Wno-ignored-attributes in the makefile,
but that was more of a work-around than an actual fix.
Thanks
Steve Groeger
IBM Runtime Technologies
Hursley, Winchester
Tel: (44) 1962 816911 Mobex: 279990 Mobile: 07718 517 129
Fax (44) 1962 816800
Lotus Notes: Steve Groeger/UK/IBM
Internet: groe...@uk.ibm.com
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
From: "Thomas Stüfe" <thomas.stu...@gmail.com>
To: Steve Groeger <groe...@uk.ibm.com>
Cc: core-libs <core-libs-dev@openjdk.java.net>
Date: 18/06/2019 13:01
Subject: Re: Question re: Usage of JNICALL with varargs function
with 32bit compilers
Hi Steve,
I always saw this as a harmless warning, safe to ignore, since both caller
and callee are forced back to the same convention so it all works out in
the end. Or can you envision a scenario where this would be harmfull?
Thank god Microsoft abandoned this calling convention circus with 64bit.
Cheers, Thomas
On Tue, Jun 18, 2019 at 1:31 PM Steve Groeger <groe...@uk.ibm.com> wrote:
Hi all,
I had a query regarding the use of JNICALL with varargs functions, which I
am hoping someone can comment on.
As explained on MSDN at [1], all functions declared as __stdcall that have
variable parameters (varargs) will be forced back to __cdecl by the MSVC.
In such case, keeping JNICALL for varargs functions/function pointers
turns out be inappropriate.
e.g.
include/jni.h
jobject (JNICALL *NewObject)
(JNIEnv *env, jclass clazz, jmethodID methodID, ...);
According to [2], stdcall does not support variadic calls in C on 32-bit
x86 targets.
When compiling a JNI native (calling NewObject) with Clang, it ends up
with the warning as follows:
...\include\jni.h:277:14: warning: stdcall calling convention ignored on
variadic function [-Wignored-attributes]
jobject (JNICALL *NewObject)
^
So basically the compiler is saying it can't do what was requested, as
such should we stop asking for JNICALL on varargs functions.
Doing so will only improve the portability of code to a wider set of
compilers.
Comments?
[1] https://msdn.microsoft.com/en-us/library/zxk0tw93.aspx
[2] https://clang.llvm.org/docs/AttributeReference.html#stdcall
Thanks
Steve Groeger
IBM Runtime Technologies
Hursley, Winchester
Tel: (44) 1962 816911 Mobex: 279990 Mobile: 07718 517 129
Fax (44) 1962 816800
Lotus Notes: Steve Groeger/UK/IBM
Internet: groe...@uk.ibm.com
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
