On Thu, 15 Feb 2024 08:46:43 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:

> This enhancement replaces uses of NULL with nullptr in the XML-description 
> files for JVMTI. These are the files `hotsport/share/prims/jvmti.xml` and 
> `hotspot/share/prims/jvmti*.xls`.
> 
> The following files are auto-generated from the `jvmti.xml` and `*.xsl files` 
> in the `build/<CFG>/variant-server/gensrc/jvmtifiles': `jvmti.h`, 
> `jvmti.html`, `jvmtiEnter.cpp`, `jvmtiEnterTrace.cpp`, `jvmtiEnv.hpp`
> 
> This addresses a category of NULL uses that wasn't dealt with by:
>  [JDK-8299837](https://bugs.openjdk.org/browse/JDK-8299837).
>  
>  Testing:
>    - TBD: run mach5 tiers1-3

Now, we this section:

Function Return Values

JVM TI functions always return an [error 
code](http://100.110.26.5:8080/view/loom/job/loom-fibers-branch-build/lastSuccessfulBuild/artifact/loom/build/linux-x64/images/docs/specs/jvmti.html#ErrorSection)
 via the 
[jvmtiError](http://100.110.26.5:8080/view/loom/job/loom-fibers-branch-build/lastSuccessfulBuild/artifact/loom/build/linux-x64/images/docs/specs/jvmti.html#jvmtiError)
 function return value. Some functions can return additional values through 
pointers provided by the calling function. In some cases, JVM TI functions 
allocate memory that your program must explicitly deallocate. This is indicated 
in the individual JVM TI function descriptions. Empty lists, arrays, sequences, 
etc are returned as `nullptr`.
In the event that the JVM TI function encounters an error (any return value 
other than `JVMTI_ERROR_NONE`) the values of memory referenced by argument 
pointers is undefined, but no memory will have been allocated and no global 
references will have been allocated. If the error occurs because of invalid 
input, no action will have occurred.

The `nullptr` is mentioned here. As I understand from the Alan's and David's 
comments above we want to clarify what does it mean for C/C++ code.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17866#issuecomment-1965473360

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