[UB] Fix a nasty place where we would pass null pointers to memcpy.

[oota-llvm.git] / include / llvm / ADT / ArrayRef.h

diff --git a/include/llvm/ADT/ArrayRef.h b/include/llvm/ADT/ArrayRef.h
index 44400d591da9b1186a48f43043d5544948963e2a..f6cc4f4e7c35ba61c84092ea7d555732724b71b4 100644 (file)
--- a/include/llvm/ADT/ArrayRef.h
+++ b/include/llvm/ADT/ArrayRef.h
@@ -11,7 +11,6 @@
 #define LLVM_ADT_ARRAYREF_H
 
 #include "llvm/ADT/None.h"
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include <vector>
 
@@ -44,19 +43,6 @@ namespace llvm {
     /// The number of elements.
     size_type Length;
 
-    /// \brief A dummy "optional" type that is only created by implicit
-    /// conversion from a reference to T.
-    ///
-    /// This type must *only* be used in a function argument or as a copy of
-    /// a function argument, as otherwise it will hold a pointer to a temporary
-    /// past that temporaries' lifetime.
-    struct TRefOrNothing {
-      const T *TPtr;
-
-      TRefOrNothing() : TPtr(nullptr) {}
-      TRefOrNothing(const T &TRef) : TPtr(&TRef) {}
-    };
-
   public:
     /// @name Constructors
     /// @{
@@ -97,12 +83,37 @@ namespace llvm {
     /*implicit*/ LLVM_CONSTEXPR ArrayRef(const T (&Arr)[N])
       : Data(Arr), Length(N) {}
 
-#if LLVM_HAS_INITIALIZER_LISTS
     /// Construct an ArrayRef from a std::initializer_list.
     /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
-    : Data(Vec.begin() == Vec.end() ? (T*)0 : Vec.begin()),
+    : Data(Vec.begin() == Vec.end() ? (T*)nullptr : Vec.begin()),
       Length(Vec.size()) {}
-#endif
+
+    /// Construct an ArrayRef<const T*> from ArrayRef<T*>. This uses SFINAE to
+    /// ensure that only ArrayRefs of pointers can be converted.
+    template <typename U>
+    ArrayRef(const ArrayRef<U *> &A,
+             typename std::enable_if<
+                 std::is_convertible<U *const *, T const *>::value>::type* = 0)
+      : Data(A.data()), Length(A.size()) {}
+
+    /// Construct an ArrayRef<const T*> from a SmallVector<T*>. This is
+    /// templated in order to avoid instantiating SmallVectorTemplateCommon<T>
+    /// whenever we copy-construct an ArrayRef.
+    template<typename U, typename DummyT>
+    /*implicit*/ ArrayRef(const SmallVectorTemplateCommon<U*, DummyT> &Vec,
+                          typename std::enable_if<
+                              std::is_convertible<U *const *,
+                                                  T const *>::value>::type* = 0)
+      : Data(Vec.data()), Length(Vec.size()) {
+    }
+
+    /// Construct an ArrayRef<const T*> from std::vector<T*>. This uses SFINAE
+    /// to ensure that only vectors of pointers can be converted.
+    template<typename U, typename A>
+    ArrayRef(const std::vector<U *, A> &Vec,
+             typename std::enable_if<
+                 std::is_convertible<U *const *, T const *>::value>::type* = 0)
+      : Data(Vec.data()), Length(Vec.size()) {}
 
     /// @}
     /// @name Simple Operations
@@ -145,6 +156,8 @@ namespace llvm {
     bool equals(ArrayRef RHS) const {
       if (Length != RHS.Length)
         return false;
+      if (Length == 0)
+        return true;
       return std::equal(begin(), end(), RHS.begin());
     }
 
@@ -189,47 +202,6 @@ namespace llvm {
       return std::vector<T>(Data, Data+Length);
     }
 
-    /// @}
-    /// @{
-    /// @name Convenience methods
-
-    /// @brief Predicate for testing that the array equals the exact sequence of
-    /// arguments.
-    ///
-    /// Will return false if the size is not equal to the exact number of
-    /// arguments given or if the array elements don't equal the argument
-    /// elements in order. Currently supports up to 16 arguments, but can
-    /// easily be extended.
-    bool equals(TRefOrNothing Arg0 = TRefOrNothing(),
-                TRefOrNothing Arg1 = TRefOrNothing(),
-                TRefOrNothing Arg2 = TRefOrNothing(),
-                TRefOrNothing Arg3 = TRefOrNothing(),
-                TRefOrNothing Arg4 = TRefOrNothing(),
-                TRefOrNothing Arg5 = TRefOrNothing(),
-                TRefOrNothing Arg6 = TRefOrNothing(),
-                TRefOrNothing Arg7 = TRefOrNothing(),
-                TRefOrNothing Arg8 = TRefOrNothing(),
-                TRefOrNothing Arg9 = TRefOrNothing(),
-                TRefOrNothing Arg10 = TRefOrNothing(),
-                TRefOrNothing Arg11 = TRefOrNothing(),
-                TRefOrNothing Arg12 = TRefOrNothing(),
-                TRefOrNothing Arg13 = TRefOrNothing(),
-                TRefOrNothing Arg14 = TRefOrNothing(),
-                TRefOrNothing Arg15 = TRefOrNothing()) {
-      TRefOrNothing Args[] = {Arg0,  Arg1,  Arg2,  Arg3, Arg4,  Arg5,
-                              Arg6,  Arg7,  Arg8,  Arg9, Arg10, Arg11,
-                              Arg12, Arg13, Arg14, Arg15};
-      if (size() > array_lengthof(Args))
-        return false;
-
-      for (unsigned i = 0, e = size(); i != e; ++i)
-        if (Args[i].TPtr == nullptr || (*this)[i] != *Args[i].TPtr)
-          return false;
-
-      // Either the size is exactly as many args, or the next arg must be null.
-      return size() == array_lengthof(Args) || Args[size()].TPtr == nullptr;
-    }
-
     /// @}
   };
 
@@ -314,6 +286,11 @@ namespace llvm {
       return MutableArrayRef<T>(data()+N, M);
     }
 
+    MutableArrayRef<T> drop_back(unsigned N) const {
+      assert(this->size() >= N && "Dropping more elements than exist");
+      return slice(0, this->size() - N);
+    }
+
     /// @}
     /// @name Operator Overloads
     /// @{