RFR: 8289093: BlockLocationPrinter fails to decode addresses with G1

[Thomas Schatzl]

On Fri, 24 Jun 2022 22:12:16 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this change that fixes an assertion failure when trying to add annotations to the hs_err file?
>> 
>> The `block_start` API from `CollectedHeap` assumes that useful values for all given addresses is returned, not asserting/crashing like some method deeper in the call chain does since [JDK-8270540](https://bugs.openjdk.org/browse/JDK-8270540), resulting in somewhat scrambled hs_err files and additional stack frames to look at in the debugger. 
>> 
>> Testing: local compilation, gha, tier1-3
>> 
>> Thanks,
>>   Thomas
>
> src/hotspot/share/gc/g1/g1CollectedHeap.cpp line 2355:
> 
>> 2353:   // outside of the allocated area.
>> 2354:   if (addr >= hr->top()) {
>> 2355:     return hr->top();
> 
> In the caller, `block_is_obj` from `if (p != NULL && CollectedHeapT::heap()->block_is_obj(p)) {` would choke on `top` as well, right? Returning `nullptr` makes more sense to me.

Or fixing `block_is_obj`...

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PR: https://git.openjdk.org/jdk19/pull/68