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V114. Dangerous explicit type pointer conversion.
The analyzer found a possible error related to the dangerous explicit type conversion of a pointer of one type to a pointer of another. The error may consist in the incorrect work with the objects to which the analyzer refers.
Let's examine an example. It contains the explicit type conversion of a 'int' pointer to a 'size_t' pointer.
int array[4] = { 1, 2, 3, 4 };
size_t *sizetPtr = (size_t *)(array);
cout << sizetPtr[1] << endl;As you can see the result of the program output is different in 32-bit and 64-bit variants. On the 32-bit system the access to the array items is correct for the sizes of 'size_t' and 'int' types coincide and we see the output "2". On the 64-bit system we got "17179869187" in output for it is this value 17179869187 which stays in the first item of array 'sizetPtr'.
The correction of the situation described consists in refusing dangerous type conversions with the help of the program modernization. Another variant is to create a new array and to copy into it the values from the original array.
Of course not all the explicit conversions of pointer types are dangerous. In the following example the work result does not depend on the system capacity for 'enum' type and 'int' type have the same size on the 32-bit system and the 64-bit system as well. So the analyzer won't show any warning messages on this code.
int array[4] = { 1, 2, 3, 4 };
enum ENumbers { ZERO, ONE, TWO, THREE, FOUR };
ENumbers *enumPtr = (ENumbers *)(array);
cout << enumPtr[1] << endl;Additional materials on this topic:
- 64-bit Lessons. Lesson 14. Pattern 6. Changing an array's type.
- 64-bit Lessons. Lesson 15. Pattern 7. Pointer packing.
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