ICorProfilerCallback2::SurvivingReferences Method

Reports the layout of objects in the heap as a result of a non-compacting garbage collection.


HRESULT SurvivingReferences(  
    [in] ULONG  cSurvivingObjectIDRanges,  
    [in, size_is(cSurvivingObjectIDRanges)] ObjectID  
                objectIDRangeStart[] ,  
    [in, size_is(cSurvivingObjectIDRanges)] ULONG  
                cObjectIDRangeLength[] );  


[in] The number of blocks of contiguous objects that survived as the result of the non-compacting garbage collection. That is, the value of cSurvivingObjectIDRanges is the size of the objectIDRangeStart and cObjectIDRangeLength arrays, which store an ObjectID and a length, respectively, for each block of objects.

The next two arguments of SurvivingReferences are parallel arrays. In other words, objectIDRangeStart and cObjectIDRangeLength concern the same block of contiguous objects.

[in] An array of ObjectID values, each of which is the starting address of a block of contiguous, live objects in memory.

[in] An array of integers, each of which is the size of a surviving block of contiguous objects in memory.

A size is specified for each block that is referenced in the objectIDRangeStart array.



This method reports sizes as MAX_ULONG for objects that are greater than 4 GB on 64-bit platforms. For objects that are larger than 4 GB, use the ICorProfilerCallback4::SurvivingReferences2 method instead.

The elements of the objectIDRangeStart and cObjectIDRangeLength arrays should be interpreted as follows to determine whether an object survived the garbage collection. Assume that an ObjectID value (ObjectID) lies within the following range:

ObjectIDRangeStart[i] <= ObjectID < ObjectIDRangeStart[i] + cObjectIDRangeLength[i]

For any value of i that is in the following range, the object has survived the garbage collection:

0 <= i < cSurvivingObjectIDRanges

A non-compacting garbage collection reclaims the memory occupied by "dead" objects, but does not compact that freed space. As a result, memory is returned to the heap, but no "live" objects are moved.

The common language runtime (CLR) calls SurvivingReferences for non-compacting garbage collections. For compacting garbage collections, ICorProfilerCallback::MovedReferences is called instead. A single garbage collection can be compacting for one generation and non-compacting for another. For a garbage collection on any particular generation, the profiler will receive either a SurvivingReferences callback or a MovedReferences callback, but not both.

Multiple SurvivingReferences callbacks might be received during a particular garbage collection, due to limited internal buffering, multiple threads reporting in the case of server garbage collection, and other reasons. In the case of multiple callbacks during a garbage collection, the information is cumulative — all references that are reported in any SurvivingReferences callback survive the garbage collection.


Platforms: See System Requirements.

Header: CorProf.idl, CorProf.h

Library: CorGuids.lib

.NET Framework Versions: Available since 2.0

See also