Refactor the malloc_info code.

malloc_info needs to be per native allocator, but the code treated it
like a global function that doesn't depend on the native memory allocator.

Update malloc debug to dump the actual pointers that it has been tracking.

Test: bionic-unit-tests pass.
Test: malloc debug tests pass.
Test: malloc hook tests pass.
Change-Id: I3b0d4d748489dd84c16d16933479dc8b8d79013e
Merged-In: I3b0d4d748489dd84c16d16933479dc8b8d79013e
(cherry picked from commit a3656a98b10d2a4a6194a5d9705ad9c2cc5877b0)
diff --git a/libc/private/MallocXmlElem.h b/libc/private/MallocXmlElem.h
new file mode 100644
index 0000000..04d3eee
--- /dev/null
+++ b/libc/private/MallocXmlElem.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdarg.h>
+#include <stdio.h>
+
+#include <private/bionic_macros.h>
+
+class MallocXmlElem {
+ public:
+  // Name must be valid throughout lifetime of the object.
+  explicit MallocXmlElem(FILE* fp, const char* name,
+                         const char* attr_fmt = nullptr, ...) : fp_(fp), name_(name) {
+    fprintf(fp, "<%s", name_);
+    if (attr_fmt != nullptr) {
+      va_list args;
+      va_start(args, attr_fmt);
+      fputc(' ', fp_);
+      vfprintf(fp_, attr_fmt, args);
+      va_end(args);
+    }
+    fputc('>', fp_);
+  }
+
+  ~MallocXmlElem() noexcept {
+    fprintf(fp_, "</%s>", name_);
+  }
+
+  void Contents(const char* fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    vfprintf(fp_, fmt, args);
+    va_end(args);
+  }
+
+private:
+  FILE* fp_;
+  const char* name_;
+
+  BIONIC_DISALLOW_IMPLICIT_CONSTRUCTORS(MallocXmlElem);
+};