Backport "Fix incomplete dumps generated by createdump (#49468)" (#49512)

The core dump generated for a app that has large GC heaps (>4GB) are don't contain all the memory needed in process. This is because of a 32bit size value overflow; changed to size_t.

Multiple customers have reported this problem in 3.1 and 5.0.

Issue: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1277488?src=WorkItemMention&src-action=artifact_link and dotnet/diagnostics#1780

Author: Mike McLaughlin

src/coreclr/src/debug/createdump/createdumpunix.cpp

@@ -45,6 +45,7 @@ CreateDump(const char* dumpPathTemplate, int pid, const char* dumpType, MINIDUMP
     }
     if (!dumpWriter.WriteDump())
     {
+        fprintf(stderr, "Writing dump FAILED\n");
         goto exit;
     }
     result = true;

src/coreclr/src/debug/createdump/dumpwriter.cpp

@@ -203,24 +203,24 @@ DumpWriter::WriteDump()
         // Only write the regions that are backed by memory
         if (memoryRegion.IsBackedByMemory())
         {
-            uint32_t size = memoryRegion.Size();
             uint64_t address = memoryRegion.StartAddress();
+            size_t size = memoryRegion.Size();
             total += size;
 
             while (size > 0)
             {
-                uint32_t bytesToRead = std::min(size, (uint32_t)sizeof(m_tempBuffer));
+                size_t bytesToRead = std::min(size, sizeof(m_tempBuffer));
                 size_t read = 0;
 
                 if (!m_crashInfo.ReadProcessMemory((void*)address, m_tempBuffer, bytesToRead, &read)) {
-                    fprintf(stderr, "ReadProcessMemory(%" PRIA PRIx64 ", %08x) FAILED\n", address, bytesToRead);
+                    fprintf(stderr, "ReadProcessMemory(%" PRIA PRIx64 ", %08zx) FAILED\n", address, bytesToRead);
                     return false;
                 }
 
                 // This can happen if the target process dies before createdump is finished
                 if (read == 0) {
-                    TRACE("ReadProcessMemory(%" PRIA PRIx64 ", %08x) return 0 bytes read\n", address, bytesToRead);
-                    break;
+                    fprintf(stderr, "ReadProcessMemory(%" PRIA PRIx64 ", %08zx) returned 0 bytes read\n", address, bytesToRead);
+                    return false;
                 }
 
                 if (!WriteData(m_tempBuffer, read)) {