Index: compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
===================================================================
--- compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
+++ compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
@@ -23,13 +23,18 @@
 }
 
 TEST(ScudoVectorTest, Stride) {
+  // Fill two pages of elements, to exercise the code that grows the buffer as
+  // needed by allocating a bigger buffer and copying the old contents in it.
+  scudo::uptr NumElements =
+      2U * scudo::getPageSizeCached() / sizeof(scudo::uptr);
+
   scudo::Vector<scudo::uptr> V;
-  for (scudo::uptr I = 0; I < 1000; I++) {
+  for (scudo::uptr I = 0; I < NumElements; I++) {
     V.push_back(I);
     EXPECT_EQ(V.size(), I + 1U);
     EXPECT_EQ(V[I], I);
   }
-  for (scudo::uptr I = 0; I < 1000; I++)
+  for (scudo::uptr I = 0; I < NumElements; I++)
     EXPECT_EQ(V[I], I);
 }
 
Index: compiler-rt/lib/scudo/standalone/vector.h
===================================================================
--- compiler-rt/lib/scudo/standalone/vector.h
+++ compiler-rt/lib/scudo/standalone/vector.h
@@ -9,14 +9,16 @@
 #ifndef SCUDO_VECTOR_H_
 #define SCUDO_VECTOR_H_
 
-#include "common.h"
+#include "mem_map.h"
 
 #include <string.h>
 
 namespace scudo {
 
-// A low-level vector based on map. May incur a significant memory overhead for
-// small vectors. The current implementation supports only POD types.
+// A low-level vector based on map. It stores the contents inline up to a fixed
+// capacity, or in an external memory buffer if it grows bigger than that. May
+// incur a significant memory overhead for small vectors. The current
+// implementation supports only POD types.
 template <typename T> class VectorNoCtor {
 public:
   constexpr void init(uptr InitialCapacity = 0) {
@@ -27,7 +29,8 @@
   }
   void destroy() {
     if (Data != &LocalData[0])
-      unmap(Data, CapacityBytes, 0, &MapData);
+      ExternalBuffer.unmap(ExternalBuffer.getBase(),
+                           ExternalBuffer.getCapacity());
   }
   T &operator[](uptr I) {
     DCHECK_LT(I, Size);
@@ -82,20 +85,26 @@
   void reallocate(uptr NewCapacity) {
     DCHECK_GT(NewCapacity, 0);
     DCHECK_LE(Size, NewCapacity);
+
+    MemMapT NewExternalBuffer;
     NewCapacity = roundUp(NewCapacity * sizeof(T), getPageSizeCached());
-    T *NewData = reinterpret_cast<T *>(
-        map(nullptr, NewCapacity, "scudo:vector", 0, &MapData));
-    memcpy(NewData, Data, Size * sizeof(T));
+    NewExternalBuffer.map(/*Addr=*/0U, NewCapacity, "scudo:vector");
+    T *NewExternalData = reinterpret_cast<T *>(NewExternalBuffer.getBase());
+
+    memcpy(NewExternalData, Data, Size * sizeof(T));
     destroy();
-    Data = NewData;
+
+    Data = NewExternalData;
     CapacityBytes = NewCapacity;
+    ExternalBuffer = NewExternalBuffer;
   }
 
   T *Data = nullptr;
-  T LocalData[256 / sizeof(T)] = {};
   uptr CapacityBytes = 0;
   uptr Size = 0;
-  [[no_unique_address]] MapPlatformData MapData = {};
+
+  T LocalData[256 / sizeof(T)] = {};
+  MemMapT ExternalBuffer;
 };
 
 template <typename T> class Vector : public VectorNoCtor<T> {