request for review (S): rev JVMTI version number

[Keith McGuigan]

On Dec 6, 2010, at 11:29 AM, Daniel D. Daugherty wrote:
> src/share/vm/prims/jvmtiEnv.cpp
>   Since JVM/TI version 1.0, 1.1 and (presumably) 1.2 are compatible
>   with each other, you don't need to do this check. The relevant
>   part of the JVM/TI spec is:
>
>   http://download.oracle.com/javase/6/docs/platform/jvmti/jvmti.html#jvmtiEnvAccess
>
>   The key sentence is:
>
>   > The returned environment may have a different version than the
>   > requested version but the returned environment must be compatible.
>
>   If a client asks for version 1.0 or version 1.1, then it is okay
>   to return version 1.2 as long as the common parts between those
>   versions are compatible. If a client running on JDK5 or JDK6 is
>   smart enough to ask for JVM/TI version 1.2, then it can be allowed
>   to have it.

Understood that the spec allows us return a different version, but it  
doesn't require it.  I'd think we'd want to leave JDK6 alone as much  
as possible, but I'll defer to your opinion in this matter.

> src/share/vm/prims/jvmtiExport.cpp
>   I don't think you need these changes either.

Right - unless we do want to keep the version constant in jdk6 (and  
jdk5 maybe someday).

> src/share/vm/prims/jvmtiH.xsl
>   This change just adds JVMTI_VERSION_1_2. It does not change the
>   JVMTI_VERSION value to the 1.2 version, but it should.

That macro gets created using the major/minor fields.  Excerpt from  
the generated jvmti.hpp:
enum {
     JVMTI_VERSION_1   = 0x30010000,
     JVMTI_VERSION_1_0 = 0x30010000,
     JVMTI_VERSION_1_1 = 0x30010100,
     JVMTI_VERSION_1_2 = 0x30010200,

     JVMTI_VERSION = 0x30000000 + (1 * 0x10000) + (2 * 0x100) + 1  /*  
version: 1.
2.1 */
};


> src/share/vm/prims/jvmtiEnvBase.hpp
>   You should add JDK17_JVMTI_VERSION to the enum set here. You should
>   also add a declaration for JvmtiEnvBase::use_version_1_2_semantics()
>   here.
>
> src/share/vm/prims/jvmtiEnvBase.cpp
>   You should add a definition for  
> JvmtiEnvBase::use_version_1_2_semantics()
>   here.

I'll do these.

> If a JVM/TI version simply adds new functions, then nothing needs to
> be done. An older agent that asks for JVM/TI version 1.0 or JVM/TI
> version 1.1 won't know about or try to use the new function.
>
> However, if a new JVM/TI version changes semantics of an existing  
> function,
> then a little more hoop jumping is needed.

What kind of hoop-jumping, exactly?  I may have to find these hoops  
and jump through them in the near future for a different fix.

--
- Keith