Actually fix issue #21484 reported by the customer.

GC heap globals like ephemeral_heap_segment and finalize_queue are
null/invalid for a server GC. Add a check to skip the workstation GC
memory enumeration if server. The server memory enumeration already
skips if workstation GC.

The dynamic module fix is still needed, createdump would have still hit
this problem after the GC heap fix.

Report the entire generation table in EnumWksGlobalMemoryRegions and
EnumSvrGlobalMemoryRegions (dotnet#20233).

src/debug/daccess/request.cpp

@@ -2814,11 +2814,14 @@ ClrDataAccess::GetGCHeapStaticData(struct DacpGcHeapDetails *detailsData)
         detailsData->generation_table[i].allocContextLimit = (CLRDATA_ADDRESS)alloc_context->alloc_limit;
     }
 
-    DPTR(dac_finalize_queue) fq = Dereference(g_gcDacGlobals->finalize_queue);
-    DPTR(uint8_t*) fillPointersTable = dac_cast<TADDR>(fq) + offsetof(dac_finalize_queue, m_FillPointers);
-    for (unsigned int i = 0; i<(*g_gcDacGlobals->max_gen + 2 + dac_finalize_queue::ExtraSegCount); i++)
+    if (g_gcDacGlobals->finalize_queue.IsValid())
     {
-        detailsData->finalization_fill_pointers[i] = (CLRDATA_ADDRESS)*TableIndex(fillPointersTable, i, sizeof(uint8_t*));
+        DPTR(dac_finalize_queue) fq = Dereference(g_gcDacGlobals->finalize_queue);
+        DPTR(uint8_t*) fillPointersTable = dac_cast<TADDR>(fq) + offsetof(dac_finalize_queue, m_FillPointers);
+        for (unsigned int i = 0; i<(*g_gcDacGlobals->max_gen + 2 + dac_finalize_queue::ExtraSegCount); i++)
+        {
+            detailsData->finalization_fill_pointers[i] = (CLRDATA_ADDRESS)*TableIndex(fillPointersTable, i, sizeof(uint8_t*));
+        }
     }
 
     SOSDacLeave();
@@ -3805,13 +3808,19 @@ ClrDataAccess::EnumWksGlobalMemoryRegions(CLRDataEnumMemoryFlags flags)
 {
     SUPPORTS_DAC;
 
+#ifdef FEATURE_SVR_GC
+    // If server GC, skip enumeration
+    if (g_gcDacGlobals->g_heaps != nullptr)
+        return;
+#endif
+
     Dereference(g_gcDacGlobals->ephemeral_heap_segment).EnumMem();
     g_gcDacGlobals->alloc_allocated.EnumMem();
     g_gcDacGlobals->gc_structures_invalid_cnt.EnumMem();
     Dereference(g_gcDacGlobals->finalize_queue).EnumMem();
 
     // Enumerate the entire generation table, which has variable size
-    size_t gen_table_size = g_gcDacGlobals->generation_size * (*g_gcDacGlobals->max_gen + 1);
+    size_t gen_table_size = g_gcDacGlobals->generation_size * (*g_gcDacGlobals->max_gen + 2);
     DacEnumMemoryRegion(dac_cast<TADDR>(g_gcDacGlobals->generation_table), gen_table_size);
 
     if (g_gcDacGlobals->generation_table.IsValid())
@@ -3826,7 +3835,6 @@ ClrDataAccess::EnumWksGlobalMemoryRegions(CLRDataEnumMemoryFlags flags)
                 while (seg)
                 {
                         DacEnumMemoryRegion(dac_cast<TADDR>(seg), sizeof(dac_heap_segment));
-
                         seg = seg->next;
                 }
             }

src/debug/daccess/request_svr.cpp

@@ -224,7 +224,7 @@ ClrDataAccess::EnumSvrGlobalMemoryRegions(CLRDataEnumMemoryFlags flags)
     {
         DPTR(dac_gc_heap) pHeap = HeapTableIndex(g_gcDacGlobals->g_heaps, i);
 
-        size_t gen_table_size = g_gcDacGlobals->generation_size * (*g_gcDacGlobals->max_gen + 1);
+        size_t gen_table_size = g_gcDacGlobals->generation_size * (*g_gcDacGlobals->max_gen + 2);
         DacEnumMemoryRegion(dac_cast<TADDR>(pHeap), sizeof(dac_gc_heap));
         DacEnumMemoryRegion(dac_cast<TADDR>(pHeap->finalize_queue), sizeof(dac_finalize_queue));
         DacEnumMemoryRegion(dac_cast<TADDR>(pHeap->generation_table), gen_table_size);