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ICorProfilerCallback::MovedReferences Method

  • Artikkeli

Called to report the new layout of objects in the heap as a result of a compacting garbage collection.

Syntax

HRESULT MovedReferences(  
    [in]  ULONG  cMovedObjectIDRanges,  
    [in, size_is(cMovedObjectIDRanges)] ObjectID oldObjectIDRangeStart[] ,  
    [in, size_is(cMovedObjectIDRanges)] ObjectID newObjectIDRangeStart[] ,  
    [in, size_is(cMovedObjectIDRanges)] ULONG    cObjectIDRangeLength[] );

Parameters

cMovedObjectIDRanges
[in] The number of blocks of contiguous objects that moved as the result of the compacting garbage collection. That is, the value of cMovedObjectIDRanges is the total size of the oldObjectIDRangeStart, newObjectIDRangeStart, and cObjectIDRangeLength arrays.

The next three arguments of MovedReferences are parallel arrays. In other words, oldObjectIDRangeStart[i], newObjectIDRangeStart[i], and cObjectIDRangeLength[i] all concern a single block of contiguous objects.

oldObjectIDRangeStart
[in] An array of ObjectID values, each of which is the old (pre-garbage collection) starting address of a block of contiguous, live objects in memory.

newObjectIDRangeStart
[in] An array of ObjectID values, each of which is the new (post-garbage collection) starting address of a block of contiguous, live objects in memory.

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

A size is specified for each block that is referenced in the oldObjectIDRangeStart and newObjectIDRangeStart arrays.

Remarks

Important

This method reports sizes as MAX_ULONG for objects that are greater than 4 GB on 64-bit platforms. To get the size of objects that are larger than 4 GB, use the ICorProfilerCallback4::MovedReferences2 method instead.

A compacting garbage collector reclaims the memory occupied by dead objects and compacts that freed space. As a result, live objects might be moved within the heap, and ObjectID values distributed by previous notifications might change.

Assume that an existing ObjectID value (oldObjectID) lies within the following range:

oldObjectIDRangeStart[i] <= oldObjectID < oldObjectIDRangeStart[i] + cObjectIDRangeLength[i]

In this case, the offset from the start of the range to the start of the object is as follows:

oldObjectID - oldObjectRangeStart[i]

For any value of i that is in the following range:

0 <= i < cMovedObjectIDRanges

you can calculate the new ObjectID as follows:

newObjectID = newObjectIDRangeStart[i] + (oldObjectID – oldObjectIDRangeStart[i])

None of the ObjectID values passed by MovedReferences are valid during the callback itself, because the garbage collection might be in the middle of moving objects from old locations to new locations. Therefore, profilers should not attempt to inspect objects during a MovedReferences call. A ICorProfilerCallback2::GarbageCollectionFinished callback indicates that all objects have been moved to their new locations and inspection can be performed.

Requirements

Platforms: See System Requirements.

Header: CorProf.idl, CorProf.h

Library: CorGuids.lib

.NET Framework Versions: Available since 2.0

See also