When Do Exception `_stackTrace` and `_stackTraceString` Get Populated?

[meriffa]

Hi,

I am investigating exceptions in a couple of Linux core dumps from ASP.NET Core 9.0 applications, running in containers (mcr.microsoft.com/dotnet/aspnet:9.0). The first core dump contains 264 exceptions and the second one 532 exceptions. Between the two dumps, only 24 exceptions have _stackTrace field populated. The rest have 0x0000000000000000 for both _stackTrace and _stackTraceString fields.

I am looking to understand the logic (or rules) that determine when the exception stack trace is populated.

My assumption is that, since stack walk is an expensive operation, exception allocation and stack trace generation are handled by different components.

Any pointers would be greatly appreciated.

Marian.

[jkotas]

The _stackTrace field is populated once the exception is thrown.

try
{
Exception e = new Exception();
// e._stackTrace is null here
throw e;
}
catch (Exception e)
{
// e._stackTrace is non-null here
}

runtime/src/coreclr/vm/excep.cpp

Lines 3134 to 3144 in 02bea82

	if (gc.pKeepAliveArray != NULL)
	{
	_ASSERTE(keepAliveItemsCount > 0);
	gc.pKeepAliveArray->SetAt(0, gc.stackTrace.m_pStackTraceArray.Get());
	((EXCEPTIONREF)ObjectFromHandle(hThrowable))->SetStackTrace(dac_cast<OBJECTREF>(gc.pKeepAliveArray));
	}
	else
	{
	_ASSERTE(keepAliveItemsCount == 0);
	((EXCEPTIONREF)ObjectFromHandle(hThrowable))->SetStackTrace(dac_cast<OBJECTREF>(gc.stackTrace.m_pStackTraceArray.Get()));
	}

is the code that populates _stackTrace.