diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -694,7 +694,7 @@
   // function. This can be called with a null buffer or zero size for buffer
   // sizing purposes.
   uptr getStats(char *Buffer, uptr Size) {
-    ScopedString Str(1024);
+    ScopedString Str;
     disable();
     const uptr Length = getStats(&Str) + 1;
     enable();
@@ -708,7 +708,7 @@
   }
 
   void printStats() {
-    ScopedString Str(1024);
+    ScopedString Str;
     disable();
     getStats(&Str);
     enable();
diff --git a/compiler-rt/lib/scudo/standalone/primary64.h b/compiler-rt/lib/scudo/standalone/primary64.h
--- a/compiler-rt/lib/scudo/standalone/primary64.h
+++ b/compiler-rt/lib/scudo/standalone/primary64.h
@@ -341,7 +341,7 @@
       if (UNLIKELY(RegionBase + MappedUser + MapSize > RegionSize)) {
         if (!Region->Exhausted) {
           Region->Exhausted = true;
-          ScopedString Str(1024);
+          ScopedString Str;
           getStats(&Str);
           Str.append(
               "Scudo OOM: The process has exhausted %zuM for size class %zu.\n",
diff --git a/compiler-rt/lib/scudo/standalone/size_class_map.h b/compiler-rt/lib/scudo/standalone/size_class_map.h
--- a/compiler-rt/lib/scudo/standalone/size_class_map.h
+++ b/compiler-rt/lib/scudo/standalone/size_class_map.h
@@ -309,7 +309,7 @@
 typedef FixedSizeClassMap<SvelteSizeClassConfig> SvelteSizeClassMap;
 
 template <typename SCMap> inline void printMap() {
-  ScopedString Buffer(1024);
+  ScopedString Buffer;
   uptr PrevS = 0;
   uptr TotalCached = 0;
   for (uptr I = 0; I < SCMap::NumClasses; I++) {
diff --git a/compiler-rt/lib/scudo/standalone/string_utils.h b/compiler-rt/lib/scudo/standalone/string_utils.h
--- a/compiler-rt/lib/scudo/standalone/string_utils.h
+++ b/compiler-rt/lib/scudo/standalone/string_utils.h
@@ -18,7 +18,7 @@
 
 class ScopedString {
 public:
-  explicit ScopedString(uptr MaxLength) : String(MaxLength), Length(0) {
+  explicit ScopedString(uptr InitialSize = 0) : String(InitialSize) {
     String[0] = '\0';
   }
   uptr length() { return Length; }
@@ -33,7 +33,7 @@
 
 private:
   Vector<char> String;
-  uptr Length;
+  uptr Length = 0;
 };
 
 int formatString(char *Buffer, uptr BufferLength, const char *Format, ...);
diff --git a/compiler-rt/lib/scudo/standalone/string_utils.cpp b/compiler-rt/lib/scudo/standalone/string_utils.cpp
--- a/compiler-rt/lib/scudo/standalone/string_utils.cpp
+++ b/compiler-rt/lib/scudo/standalone/string_utils.cpp
@@ -219,7 +219,7 @@
 }
 
 void ScopedString::append(const char *Format, va_list Args) {
-  DCHECK_LT(Length, String.size());
+  RAW_CHECK(Length <= String.size());
   va_list ArgsCopy;
   va_copy(ArgsCopy, Args);
   // formatString doesn't currently support a null buffer or zero buffer length,
@@ -228,11 +228,12 @@
   char C[1];
   const uptr AdditionalLength =
       static_cast<uptr>(formatString(C, sizeof(C), Format, Args)) + 1;
+  // append will silently fail if the underlying Vector can't grow.
   String.resize(Length + AdditionalLength);
   formatString(String.data() + Length, AdditionalLength, Format, ArgsCopy);
-  va_end(ArgsCopy);
   Length = strlen(String.data());
-  CHECK_LT(Length, String.size());
+  RAW_CHECK(Length < String.size());
+  va_end(ArgsCopy);
 }
 
 FORMAT(2, 3)
@@ -247,7 +248,7 @@
 void Printf(const char *Format, ...) {
   va_list Args;
   va_start(Args, Format);
-  ScopedString Msg(1024);
+  ScopedString Msg;
   Msg.append(Format, Args);
   outputRaw(Msg.data());
   va_end(Args);
diff --git a/compiler-rt/lib/scudo/standalone/tests/primary_test.cpp b/compiler-rt/lib/scudo/standalone/tests/primary_test.cpp
--- a/compiler-rt/lib/scudo/standalone/tests/primary_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/primary_test.cpp
@@ -132,7 +132,7 @@
   }
   Cache.destroy(nullptr);
   Allocator->releaseToOS();
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Allocator->getStats(&Str);
   Str.output();
 }
@@ -178,7 +178,7 @@
   }
   Cache.destroy(nullptr);
   Allocator.releaseToOS();
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Allocator.getStats(&Str);
   Str.output();
   EXPECT_EQ(AllocationFailed, true);
@@ -216,7 +216,7 @@
   }
   Cache.destroy(nullptr);
   Allocator->releaseToOS();
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Allocator->getStats(&Str);
   Str.output();
 }
@@ -263,7 +263,7 @@
   for (auto &T : Threads)
     T.join();
   Allocator->releaseToOS();
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Allocator->getStats(&Str);
   Str.output();
 }
diff --git a/compiler-rt/lib/scudo/standalone/tests/quarantine_test.cpp b/compiler-rt/lib/scudo/standalone/tests/quarantine_test.cpp
--- a/compiler-rt/lib/scudo/standalone/tests/quarantine_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/quarantine_test.cpp
@@ -214,7 +214,7 @@
   Quarantine.drainAndRecycle(&Cache, Cb);
   EXPECT_EQ(Cache.getSize(), 0UL);
 
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Quarantine.getStats(&Str);
   Str.output();
 }
@@ -246,7 +246,7 @@
   for (scudo::uptr I = 0; I < NumberOfThreads; I++)
     pthread_join(T[I].Thread, 0);
 
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   Quarantine.getStats(&Str);
   Str.output();
 
diff --git a/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp b/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
--- a/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
@@ -64,7 +64,7 @@
     L->deallocate(scudo::Options{}, V.back());
     V.pop_back();
   }
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   L->getStats(&Str);
   Str.output();
   L->unmapTestOnly();
@@ -122,7 +122,7 @@
       }
     }
   }
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   L->getStats(&Str);
   Str.output();
   L->unmapTestOnly();
@@ -146,7 +146,7 @@
     L->deallocate(scudo::Options{}, V.back());
     V.pop_back();
   }
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   L->getStats(&Str);
   Str.output();
   L->unmapTestOnly();
@@ -217,7 +217,7 @@
   }
   for (auto &T : Threads)
     T.join();
-  scudo::ScopedString Str(1024);
+  scudo::ScopedString Str;
   L->getStats(&Str);
   Str.output();
   L->unmapTestOnly();
diff --git a/compiler-rt/lib/scudo/standalone/tests/vector_test.cpp b/compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
--- a/compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/vector_test.cpp
@@ -24,13 +24,13 @@
 
 TEST(ScudoVectorTest, Stride) {
   scudo::Vector<int> V;
-  for (int i = 0; i < 1000; i++) {
-    V.push_back(i);
-    EXPECT_EQ(V.size(), i + 1U);
-    EXPECT_EQ(V[i], i);
+  for (scudo::uptr I = 0; I < 1000; I++) {
+    V.push_back(I);
+    EXPECT_EQ(V.size(), I + 1U);
+    EXPECT_EQ(V[I], I);
   }
-  for (int i = 0; i < 1000; i++)
-    EXPECT_EQ(V[i], i);
+  for (scudo::uptr I = 0; I < 1000; I++)
+    EXPECT_EQ(V[I], I);
 }
 
 TEST(ScudoVectorTest, ResizeReduction) {
diff --git a/compiler-rt/lib/scudo/standalone/vector.h b/compiler-rt/lib/scudo/standalone/vector.h
--- a/compiler-rt/lib/scudo/standalone/vector.h
+++ b/compiler-rt/lib/scudo/standalone/vector.h
@@ -19,14 +19,13 @@
 // small vectors. The current implementation supports only POD types.
 template <typename T> class VectorNoCtor {
 public:
-  void init(uptr InitialCapacity) {
-    CapacityBytes = 0;
-    Size = 0;
-    Data = nullptr;
+  void init(uptr InitialCapacity = 0) {
+    Data = reinterpret_cast<T *>(&LocalData[0]);
+    CapacityBytes = sizeof(LocalData);
     reserve(InitialCapacity);
   }
   void destroy() {
-    if (Data)
+    if (Data != reinterpret_cast<T *>(&LocalData[0]))
       unmap(Data, CapacityBytes);
   }
   T &operator[](uptr I) {
@@ -82,26 +81,24 @@
   void reallocate(uptr NewCapacity) {
     DCHECK_GT(NewCapacity, 0);
     DCHECK_LE(Size, NewCapacity);
-    const uptr NewCapacityBytes =
-        roundUpTo(NewCapacity * sizeof(T), getPageSizeCached());
+    NewCapacity = roundUpTo(NewCapacity * sizeof(T), getPageSizeCached());
     T *NewData =
-        reinterpret_cast<T *>(map(nullptr, NewCapacityBytes, "scudo:vector"));
-    if (Data) {
-      memcpy(NewData, Data, Size * sizeof(T));
-      unmap(Data, CapacityBytes);
-    }
+        reinterpret_cast<T *>(map(nullptr, NewCapacity, "scudo:vector"));
+    memcpy(NewData, Data, Size * sizeof(T));
+    destroy();
     Data = NewData;
-    CapacityBytes = NewCapacityBytes;
+    CapacityBytes = NewCapacity;
   }
 
-  T *Data;
-  uptr CapacityBytes;
-  uptr Size;
+  T *Data = nullptr;
+  u8 LocalData[256] = {};
+  uptr CapacityBytes = 0;
+  uptr Size = 0;
 };
 
 template <typename T> class Vector : public VectorNoCtor<T> {
 public:
-  Vector() { VectorNoCtor<T>::init(1); }
+  Vector() { VectorNoCtor<T>::init(); }
   explicit Vector(uptr Count) {
     VectorNoCtor<T>::init(Count);
     this->resize(Count);