Deallocate resources for DacDbiArrayList with a matching deallocator (#…

…58791)

Deleted InfoStoreForDbiNew as there were no users.

Added DeleteDbiMemory to deal with destruction of items and proper usage of the corresponding allocator. However, using this custom new here across dll boundaries is risky as the T type will get its destructor called then the array list is destructed. The old implementation that used the CLR allocators didn't call the destructors on the inner elements (we had a potential leak, in practice it wasn't very noticeable - most objects are never deleted). After #55945, the standard array delete expression - as well as this change - call the destructor on every object. Currently, the instantiations of this type are all devoid of special destructors and are largely blittable structs, so this remains working as it was:

- ICorDebugInfo::NativeVarInfo
- GUID
- FieldData
- DebuggerIPCE_TypeArgData
- DebuggerIPCE_ExpandedTypeData
- DebuggerIPCE_BasicTypeData
- DebuggerILToNativeMap
- DacExceptionCallStackData
- CordbType *
- CORDB_ADDRESS
- COR_SEGMENT
- COR_MEMORY_RA

src/coreclr/debug/daccess/dacdbiimpl.cpp

@@ -78,7 +78,7 @@ IDacDbiInterface::IAllocator * g_pAllocator = NULL;
 //            return; // DBI will then free this memory.
 //        }
 //        ...
-//        DeleteDbiMemory(p);
+//        DeleteDbiMemory(p); // DeleteDbiMemory(p, len); if it was an array allocation.
 //     }
 //
 //     Be very careful when using this on classes since Dbi and DAC may be in
@@ -155,6 +155,25 @@ template<class T> void DeleteDbiMemory(T *p)
     g_pAllocator->Free((BYTE*) p);
 }
 
+// Delete memory and invoke dtor for memory allocated with 'operator (forDbi) new[]'
+// There's an inherent risk here - where each element's destructor will get called within
+// the context of the DAC. If the destructor tries to use the CRT allocator logic expecting
+// to hit the DBI's, we could be in trouble. Those objects need to use an export allocator like this.
+template<class T> void DeleteDbiArrayMemory(T *p, int count)
+{
+    if (p == NULL)
+    {
+        return;
+    }
+
+    for (T *cur = p; cur < p + count; cur++)
+    {
+        cur->~T();
+    }
+
+    _ASSERTE(g_pAllocator != NULL);
+    g_pAllocator->Free((BYTE*) p);
+}
 
 //---------------------------------------------------------------------------------------
 // Creates the DacDbiInterface object, used by Dbi.
@@ -818,12 +837,6 @@ SIZE_T DacDbiInterfaceImpl::GetArgCount(MethodDesc * pMD)
     return NumArguments;
 } //GetArgCount
 
-// Allocator to pass to DebugInfoStores, allocating forDBI
-BYTE* InfoStoreForDbiNew(void * pData, size_t cBytes)
-{
-    return new(forDbi) BYTE[cBytes];
-}
-
 // Allocator to pass to the debug-info-stores...
 BYTE* InfoStoreNew(void * pData, size_t cBytes)
 {

src/coreclr/debug/di/rspriv.h

@@ -168,12 +168,16 @@ struct MachineInfo
     USHORT m_usPort;
 };
 
+#ifdef DACCESS_COMPILE
+    #error This header cannot be used in the DAC
+#endif
+
 extern forDbiWorker forDbi;
 
 // for dbi we just default to new, but we need to have these defined for both dac and dbi
 inline void * operator new(size_t lenBytes, const forDbiWorker &)
 {
-    void * result = new BYTE[lenBytes];
+    void * result = new (nothrow) BYTE[lenBytes];
     if (result == NULL)
     {
         ThrowOutOfMemory();
@@ -183,7 +187,7 @@ inline void * operator new(size_t lenBytes, const forDbiWorker &)
 
 inline void * operator new[](size_t lenBytes, const forDbiWorker &)
 {
-    void * result = new BYTE[lenBytes];
+    void * result = new (nothrow) BYTE[lenBytes];
     if (result == NULL)
     {
         ThrowOutOfMemory();
@@ -198,6 +202,11 @@ void DeleteDbiMemory(T *p)
     delete p;
 }
 
+template<class T> inline
+void DeleteDbiArrayMemory(T *p, int)
+{
+    delete[] p;
+}
 
 
 //---------------------------------------------------------------------------------------

src/coreclr/debug/inc/dacdbiinterface.h

@@ -29,6 +29,7 @@
 //    In the DBI implementation, this can directly call delete (assuming the IAllocator::Free
 //    directly called new).
 template<class T> void DeleteDbiMemory(T *p);
+template<class T> void DeleteDbiArrayMemory(T *p, int count);
 // Need a class to serve as a tag that we can use to overload New/Delete.
 class forDbiWorker {};
 extern forDbiWorker forDbi;

src/coreclr/debug/inc/dacdbistructures.inl

@@ -71,7 +71,7 @@ void DacDbiArrayList<T>::Dealloc()
 
     if (m_pList != NULL)
     {
-        delete [] m_pList;
+        DeleteDbiArrayMemory(m_pList, m_nEntries);
         m_pList = NULL;
     }
     m_nEntries = 0;