Something is wrong with JNI's jlong in JDK7

[Scott Palmer]

On 2012-11-13, at 5:00 PM, Scott Palmer <swpalmer at gmail.com> wrote:

> On 2012-11-13, at 4:36 PM, Mike Swingler <swingler at apple.com> wrote:
> 
>> On Nov 13, 2012, at 8:21 AM, Scott Palmer <swpalmer at gmail.com> wrote:
>> 
>>> I just noticed that the criteria for defining jlong has changed from that given in Apple's JDK 6 vs. Oracle's JDK 7.  This caused some code of mine to break because it seems to be wrong under some circumstances.
>>> 
>>> JDK 7u10 has this.  Note that sometimes a jlong is a C "long" and sometimes it is a C "long long": 
>>> 
>>> #ifndef _JAVASOFT_JNI_MD_H_
>>> #define _JAVASOFT_JNI_MD_H_
>>> 
>>> #define JNIEXPORT
>>> #define JNIIMPORT
>>> #define JNICALL
>>> 
>>> typedef int jint;
>>> #ifdef _LP64 /* 64-bit Solaris */
>>> typedef long jlong;
>>> #else
>>> typedef long long jlong;
>>> #endif
>>> 
>>> typedef signed char jbyte;
>>> 
>>> #endif /* !_JAVASOFT_JNI_MD_H_ */
>>> 
>>> 
>>> 
>>> Whereas Apple's JDK 6 always uses "long long":
>>> 
>>> 
>>> 
>>> #ifndef _JAVASOFT_JNI_MD_H_
>>> #define _JAVASOFT_JNI_MD_H_
>>> 
>>> #define JNIEXPORT __attribute__((visibility("default")))
>>> #define JNIIMPORT
>>> #define JNICALL
>>> 
>>> #if defined(__LP64__) && __LP64__ /* for -Wundef */
>>> typedef int jint;
>>> #else
>>> typedef long jint;
>>> #endif
>>> typedef long long jlong;
>>> typedef signed char jbyte;
>>> 
>>> #endif /* !_JAVASOFT_JNI_MD_H_ */
>> 
>> Have you filed a bug at <http://bugs.sun.com>?
> 
> Just…  I filed it against "javah" since there was no more appropriate category available.
> 

Just in case anyone is wondering why this matters.  The C++ linkage breaks because func(long) - a method taking the Java 7 version of jlong, and func(long long) a method taking the Java 6 version of jlong, are considered different, even though both types are 8 bytes.  C++ name mangling comes out different.

We have a Java project that uses a lot of native code and depends a lot on a plugin mechanism where the plugins need to link with a native library we provide as well.  When our library is compiled with Java 6 headers, plugins compiled against Java 7 headers can't link with it.

I neglected to point that out in my bug report (Review ID: 2381559), and I have not yet got any confirmation that it was accepted.

Scott