bug669.cpp

1    #include <string.h>
2
3    class X
4        {
5        int *p;
6      public:
7        X()
8            { p = new int[20]; }
9        void init()
10           { if(p) memset( p, 20, 'a' ); }
11       ~X()
12           { delete[] p; }
13       };

There is a significant problem with this class that would make it behave irrationally. Can you find it?

bug669.cpp lint Output

--- Module:   bug669.cpp
              _
        { p = new int[20]; }
bug669.cpp(8) : Info 1732: new in constructor for class X which has no
    assignment operator
bug669.cpp(8) : Info 1733: new in constructor for class X which has no
    copy constructor
                                    _
        { if(p) memset( p, 20, 'a' ); }
bug669.cpp(10) : Warning 669: Possible data overrun for function
    memset(void *, int, unsigned int), argument 3 exceeds argument 1

    --- Wrap-up for Module: bug669.cpp

Info 753: local class X (line 3, file bug669.cpp) not referenced

Reference Manual Explanation

669    Possible data overrun for function Symbol, argument Integer
       exceeds argument Integer  -- This message is for data transfer
       functions such as memcpy, strcpy, fgets, etc. when the size
       indicated by the first cited argument (or arguments) can possibly
       exceed the size of the buffer area cited by the second.  The
       message may also be issued for user functions via the -function
       option. See Function Mimicry and Value Tracking.