8017478: Kitchensink crashed with SIGSEGV in BaselineReporter::diff_callsites

Summary: Fixed possible NULL pointer that caused SIGSEGV
Reviewed-by: coleenp, acorn, ctornqvi

src/share/vm/services/memReporter.cpp

@@ -188,8 +188,8 @@ void BaselineReporter::diff_callsites(const MemBaseline& cur, const MemBaseline&
                   (MallocCallsitePointer*)prev_malloc_itr.current();
 
   while (cur_malloc_callsite != NULL || prev_malloc_callsite != NULL) {
-    if (prev_malloc_callsite == NULL ||
-        cur_malloc_callsite->addr() < prev_malloc_callsite->addr()) {
+    if (prev_malloc_callsite == NULL) {
+      assert(cur_malloc_callsite != NULL, "sanity check");
       // this is a new callsite
       _outputer.diff_malloc_callsite(cur_malloc_callsite->addr(),
         amount_in_current_scale(cur_malloc_callsite->amount()),
@@ -197,15 +197,34 @@ void BaselineReporter::diff_callsites(const MemBaseline& cur, const MemBaseline&
         diff_in_current_scale(cur_malloc_callsite->amount(), 0),
         diff(cur_malloc_callsite->count(), 0));
       cur_malloc_callsite = (MallocCallsitePointer*)cur_malloc_itr.next();
-    } else if (cur_malloc_callsite == NULL ||
-               cur_malloc_callsite->addr() > prev_malloc_callsite->addr()) {
+    } else if (cur_malloc_callsite == NULL) {
+      assert(prev_malloc_callsite != NULL, "Sanity check");
       // this callsite is already gone
       _outputer.diff_malloc_callsite(prev_malloc_callsite->addr(),
-        amount_in_current_scale(0), 0,
+        0, 0,
         diff_in_current_scale(0, prev_malloc_callsite->amount()),
         diff(0, prev_malloc_callsite->count()));
       prev_malloc_callsite = (MallocCallsitePointer*)prev_malloc_itr.next();
-    } else {  // the same callsite
+    } else {
+      assert(cur_malloc_callsite  != NULL,  "Sanity check");
+      assert(prev_malloc_callsite != NULL,  "Sanity check");
+      if (cur_malloc_callsite->addr() < prev_malloc_callsite->addr()) {
+        // this is a new callsite
+        _outputer.diff_malloc_callsite(cur_malloc_callsite->addr(),
+          amount_in_current_scale(cur_malloc_callsite->amount()),
+          cur_malloc_callsite->count(),
+          diff_in_current_scale(cur_malloc_callsite->amount(), 0),
+          diff(cur_malloc_callsite->count(), 0));
+          cur_malloc_callsite = (MallocCallsitePointer*)cur_malloc_itr.next();
+      } else if (cur_malloc_callsite->addr() > prev_malloc_callsite->addr()) {
+        // this callsite is already gone
+        _outputer.diff_malloc_callsite(prev_malloc_callsite->addr(),
+          0, 0,
+          diff_in_current_scale(0, prev_malloc_callsite->amount()),
+          diff(0, prev_malloc_callsite->count()));
+        prev_malloc_callsite = (MallocCallsitePointer*)prev_malloc_itr.next();
+      } else {
+        // the same callsite
         _outputer.diff_malloc_callsite(cur_malloc_callsite->addr(),
           amount_in_current_scale(cur_malloc_callsite->amount()),
           cur_malloc_callsite->count(),
@@ -215,6 +234,7 @@ void BaselineReporter::diff_callsites(const MemBaseline& cur, const MemBaseline&
         prev_malloc_callsite = (MallocCallsitePointer*)prev_malloc_itr.next();
       }
     }
+  }
 
   // walk virtual memory callsite
   MemPointerArrayIteratorImpl cur_vm_itr(pBL_cur->_vm_cs);