[scudo] Add static vector functionality.

compiler-rt/lib/scudo/standalone/string_utils.h

@@ -40,7 +40,7 @@ class ScopedString {
   void appendString(int Width, int MaxChars, const char *S);
   void appendPointer(u64 ptr_value);
 
-  Vector<char> String;
+  Vector<char, 256> String;
 };
 
 void Printf(const char *Format, ...) FORMAT(1, 2);

compiler-rt/lib/scudo/standalone/tests/vector_test.cpp

@@ -11,7 +11,7 @@
 #include "vector.h"
 
 TEST(ScudoVectorTest, Basic) {
-  scudo::Vector<int> V;
+  scudo::Vector<int, 64U> V;
   EXPECT_EQ(V.size(), 0U);
   V.push_back(42);
   EXPECT_EQ(V.size(), 1U);
@@ -23,7 +23,7 @@ TEST(ScudoVectorTest, Basic) {
 }
 
 TEST(ScudoVectorTest, Stride) {
-  scudo::Vector<scudo::uptr> V;
+  scudo::Vector<scudo::uptr, 32U> V;
   for (scudo::uptr I = 0; I < 1000; I++) {
     V.push_back(I);
     EXPECT_EQ(V.size(), I + 1U);
@@ -34,7 +34,7 @@ TEST(ScudoVectorTest, Stride) {
 }
 
 TEST(ScudoVectorTest, ResizeReduction) {
-  scudo::Vector<int> V;
+  scudo::Vector<int, 64U> V;
   V.push_back(0);
   V.push_back(0);
   EXPECT_EQ(V.size(), 2U);
@@ -48,7 +48,7 @@ TEST(ScudoVectorTest, ResizeReduction) {
 
 // Verify that if the reallocate fails, nothing new is added.
 TEST(ScudoVectorTest, ReallocateFails) {
-  scudo::Vector<char> V;
+  scudo::Vector<char, 256U> V;
   scudo::uptr capacity = V.capacity();
 
   // Get the current address space size.

compiler-rt/lib/scudo/standalone/vector.h

@@ -21,7 +21,7 @@ namespace scudo {
 // implementation supports only POD types.
 //
 // NOTE: This class is not meant to be used directly, use Vector<T> instead.
-template <typename T> class VectorNoCtor {
+template <typename T, size_t StaticNumEntries> class VectorNoCtor {
 public:
   T &operator[](uptr I) {
     DCHECK_LT(I, Size);
@@ -116,18 +116,21 @@ template <typename T> class VectorNoCtor {
   uptr CapacityBytes = 0;
   uptr Size = 0;
 
-  T LocalData[256 / sizeof(T)] = {};
+  T LocalData[StaticNumEntries] = {};
   MemMapT ExternalBuffer;
 };
 
-template <typename T> class Vector : public VectorNoCtor<T> {
+template <typename T, size_t StaticNumEntries>
+class Vector : public VectorNoCtor<T, StaticNumEntries> {
 public:
-  constexpr Vector() { VectorNoCtor<T>::init(); }
+  static_assert(StaticNumEntries > 0U,
+                "Vector must have a non-zero number of static entries.");
+  constexpr Vector() { VectorNoCtor<T, StaticNumEntries>::init(); }
   explicit Vector(uptr Count) {
-    VectorNoCtor<T>::init(Count);
+    VectorNoCtor<T, StaticNumEntries>::init(Count);
     this->resize(Count);
   }
-  ~Vector() { VectorNoCtor<T>::destroy(); }
+  ~Vector() { VectorNoCtor<T, StaticNumEntries>::destroy(); }
   // Disallow copies and moves.
   Vector(const Vector &) = delete;
   Vector &operator=(const Vector &) = delete;