RFR: 8034025 Remove JPLIS agent dependency on canonicalize_md.c

[Staffan Larsen]

On 6 mar 2014, at 11:33, Alan Bateman <Alan.Bateman at oracle.com> wrote:

> On 06/03/2014 08:11, Staffan Larsen wrote:
>> 
>> The JPLIS agent (libinstrument.so) compiles in code from libjava, specifically the file functions in canonicalize_md.c. This dependence has been there for a long time and will need to be changed to re-organize the JDK sources so that the code is organized by module.
>> 
>> With this change the instrument library links the same method dynamically at runtime instead of statically at compile time.
>> 
>> webrev: http://cr.openjdk.java.net/~sla/8034025/webrev.00/
>> bug: https://bugs.openjdk.java.net/browse/JDK-8034025
>> testing: the jdk_instrument target in jprt
>> 
> It's good to fix this dependency as it was always odd to compile into this libinstrument.
> 
> I'm now sure about adding -ljava to LIBINSTRUMENT_LDFLAGS_SUFFIX as I would this would need to be $(WIN_JAVA_LIB) on Windows. That is, I suspect  LDFLAGS_SUFFIX_<platform> needs to be used here.

I’m not sure how these things work, but I’ve built and tested this on all platforms, so it seemed to work. I see that WIN_JAVA_LIB is already added on windows so perhaps that is why. I’ve changed the fix slightly to remove the -ljava from the windows LDFLAGS and verified that it builds and tests on all platforms.

> The return from the JNI GetEnv isn't currently checked but for now I'll just believe the comment that the thread calling Agent_OnLoad early in the startup is already attached. As the JNIEnv parameter isn't used then it doesn't matter of course but the temptation may be to use it with other JNI functions that may not be usable early in the startup.

This turned out to be a mistake. According to the JVMTI spec, the agent does not have access to the JNIEnv during Agent_OnLoad(). Since Canonicalize() does not use the value it didn’t matter what I sent to it.

I would like to continue sending NULL to Canonicalize() as the JNIEnv since there is no way I can get a correct env in Agent_OnLoad. It would not be correct, but it would work.

The other option is to add a Canonicalize_NoEnv() function to libjava that does not take a JNIEnv parameter.

Thoughts on this?


> As Canonicalize is not in FileSystemSupport.c then maybe it would be better to remove the function prototype from the header file and just declare it as an extern in appendBootClassPath where it is used.

OK. 

webrev: http://cr.openjdk.java.net/~sla/8034025/webrev.01/

/Staffan


> Otherwise thank for doing this.
> 
> -Alan

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