RFR: 8311993: Test serviceability/sa/UniqueVtableTest.java failed: duplicate vtables detected [v2]

[Chris Plummer]

On Mon, 26 Aug 2024 22:25:34 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> On Windows SA agent gets a class vtable from symbols, exported from jvm.dll (it exports symbols like "??_7" + type + "@@6B@").
>> But symbol lookup function first requests WinDbg about the symbol.
>> Sometimes WinDbg routine IDebugSymbols::GetOffsetByName() returns offset for both class and class pointer types. Returned offsets correspond to symbols like "jvm!class_name::`vftable'".
>> The behavior is intermittent, I was not able to find what is the reason.
>> The fix adds workaround for the case - if GetOffsetByName succeeded, we check if corresponding symbol contains requested one.
>> So it returns expected offset for non-vtable symbols like "MaxJNILocalCapacity" (GetOffsetByName returns offset for "jvm!MaxJNILocalCapacity"), but returns 0 for vtlb lookup.
>> 
>> Additionally added check for results of IDebugSymbols::SetImagePath/SetSymbolPath
>> 
>> Testing: tier1,tier2,hs-tier5-svc
>
> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   use SYMBOL_BUFSIZE

I found this:


    // should we parse DLL symbol table in Java code or use
    // Windbg's native lookup facility? By default, we use
    // native lookup so that we can take advantage of '.pdb'
    // files, if available.
    useNativeLookup = true;
    String str = System.getProperty("sun.jvm.hotspot.debugger.windbg.disableNativeLookup");
    if (str != null) {
      useNativeLookup = false;
    }


I'm not sure what is meant by "take advantage of '.pbp' files". Is it perhaps a more reliable or complete database of symbols, or perhaps it is faster? In any case, I'd be interested in seeing if all our tests still pass when useNativeLookup is false.

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PR Comment: https://git.openjdk.org/jdk/pull/20684#issuecomment-2311592258