Changeset 80373 in vbox for trunk/include/VBox

Timestamp:

Aug 21, 2019 2:51:02 PM (5 years ago)

Author:

vboxsync

Message:

com/array.h: handling empty base elements better (hopefully will eliminate static code analysis issues) by using a const array as the representation.

File:

• trunk/include/VBox/com/array.h (modified) (15 diffs)

trunk/include/VBox/com/array.h

@@ -224 +224 @@
 {
 
+/** Used for dummy element access in com::SafeArray, avoiding crashes. */
+extern const char Zeroes[16];
+
+
 #ifdef VBOX_WITH_XPCOM
 
@@ -618 +622 @@
      * Creates a null array.
      */
-    SafeArray() {}
+    SafeArray() { }
 
     /**
@@ -734 +738 @@
         AssertReturnVoid(!isNull());
 
-        int i = 0;
+        size_t i = 0;
         for (typename Map::const_iterator it = aMap.begin();
              it != aMap.end(); ++ it, ++ i)
@@ -935 +939 @@
     /**
      * Array access operator that returns an array element by reference. A bit
-     * safer than #raw(): asserts and returns an invalid reference if this
-     * instance is null or if the index is out of bounds.
+     * safer than #raw(): asserts and returns a reference to a static zero
+     * element (const, i.e. writes will fail) if this instance is null or
+     * if the index is out of bounds.
      *
      * @note For weak instances, this call will succeed but the behavior of
@@ -944 +949 @@
     T &operator[] (size_t aIdx)
     {
-        AssertReturn(m.arr != NULL,  *((T *)NULL));
-        AssertReturn(aIdx < size(), *((T *)NULL));
+        /** @todo r=klaus should do this as a AssertCompile, but cannot find a way which works. */
+        Assert(sizeof(T) <= sizeof(Zeroes));
+        AssertReturn(m.arr != NULL, *(T *)&Zeroes[0]);
+        AssertReturn(aIdx < size(), *(T *)&Zeroes[0]);
 #ifdef VBOX_WITH_XPCOM
         return m.arr[aIdx];
 #else
-        AssertReturn(m.raw != NULL,  *((T *)NULL));
+        AssertReturn(m.raw != NULL, *(T *)&Zeroes[0]);
         return m.raw[aIdx];
 #endif
@@ -959 +966 @@
     const T operator[] (size_t aIdx) const
     {
-        AssertReturn(m.arr != NULL,  *((T *)1));
-        AssertReturn(aIdx < size(), *((T *)1));
+        AssertReturn(m.arr != NULL, *(const T *)&Zeroes[0]);
+        AssertReturn(aIdx < size(), *(const T *)&Zeroes[0]);
 #ifdef VBOX_WITH_XPCOM
         return m.arr[aIdx];
 #else
-        AssertReturn(m.raw != NULL,  *((T *)NULL));
+        AssertReturn(m.raw != NULL, *(const T *)&Zeroes[0]);
         return m.raw[aIdx];
 #endif
@@ -1377 +1384 @@
     public:
 
-        nsIDRef(nsID * &aVal) : mVal(aVal) {}
-
-        operator const nsID &() const { return mVal ? *mVal : *Empty; }
-        operator nsID() const { return mVal ? *mVal : *Empty; }
-
-        const nsID *operator&() const { return mVal ? mVal : Empty; }
+        nsIDRef(nsID * &aVal) : mVal(aVal) { AssertCompile(sizeof(nsID) <= sizeof(Zeroes)); }
+
+        operator const nsID &() const { return mVal ? *mVal : *(const nsID *)&Zeroes[0]; }
+        operator nsID() const { return mVal ? *mVal : *(nsID *)&Zeroes[0]; }
+
+        const nsID *operator&() const { return mVal ? mVal : (const nsID *)&Zeroes[0]; }
 
         nsIDRef &operator= (const nsID &aThat)
@@ -1397 +1404 @@
         nsID * &mVal;
 
-        static const nsID *Empty;
-
         friend class SafeGUIDArray;
     };
@@ -1430 +1435 @@
         Assert(m.arr != NULL);
         Assert(aIdx < size());
-        return m.arr[aIdx] ? *m.arr[aIdx] : *nsIDRef::Empty;
+        return m.arr[aIdx] ? *m.arr[aIdx] : *(const nsID *)&Zeroes[0];
     }
 };
@@ -1448 +1453 @@
 
     /** See SafeArray<>::SafeArray(). */
-    SafeConstGUIDArray() {}
+    SafeConstGUIDArray() { AssertCompile(sizeof(nsID) <= sizeof(Zeroes)); }
 
     /* See SafeArray<>::SafeArray(ComSafeArrayIn(T, aArg)). */
@@ -1463 +1468 @@
     const nsID &operator[] (size_t aIdx) const
     {
-        AssertReturn(m.arr != NULL,  **((const nsID * *)1));
-        AssertReturn(aIdx < size(), **((const nsID * *)1));
+        AssertReturn(m.arr != NULL,  *(const nsID *)&Zeroes[0]);
+        AssertReturn(aIdx < size(), *(const nsID *)&Zeroes[0]);
         return *m.arr[aIdx];
     }
@@ -1656 +1661 @@
         AssertReturnVoid(!Base::isNull());
 
-        int i = 0;
+        size_t i = 0;
         for (typename List::const_iterator it = aCntr.begin();
              it != aCntr.end(); ++ it, ++ i)
@@ -1685 +1690 @@
         AssertReturnVoid(!Base::isNull());
 
-        int i = 0;
+        size_t i = 0;
         for (typename List::const_iterator it = aCntr.begin();
              it != aCntr.end(); ++ it, ++ i)
@@ -1717 +1722 @@
         AssertReturnVoid(!Base::isNull());
 
-        int i = 0;
+        size_t i = 0;
         for (typename Map::const_iterator it = aMap.begin();
              it != aMap.end(); ++ it, ++ i)
@@ -1749 +1754 @@
         AssertReturnVoid(!Base::isNull());
 
-        int i = 0;
+        size_t i = 0;
         for (typename Map::const_iterator it = aMap.begin();
              it != aMap.end(); ++ it, ++ i)