bug416.cpp

1    #define N_CUST 10000    // no. of customers
2    #define LIMIT 20        // limit per customer
3    int liters[N_CUST];     // liters consumed
4    int *upper_bound(int);
5
6    int main()          // Oktoberfest Limit Checker
7        {
8        for( int *p = liters; p < upper_bound(N_CUST+1); p++ )
9            {
10           *p = 0;     // initialize liters to 0
11           }
12       return 0;
13       }
14
15   int *upper_bound( int bound )
16       {
17       return liters+bound;
18       }

This is the start of a larger program to monitor beer consumption at a large gathering, but the program already has a serious problem. Can you spot it?

bug416.cpp lint Output

--- Module:   bug416.cpp

During Specific Walk:
  File bug416.cpp line 8: upper_bound(10001)
bug416.cpp  17  Warning 416: Likely creation of out-of-bounds pointer (2 beyond
    end of data) by operator 'ptr+int' [Reference: file bug416.cpp: lines 8, 17]

    --- Wrap-up for Module: bug416.cpp

Info 750: local macro 'LIMIT' (line 2, file bug416.cpp) not referenced

Reference Manual Explanation

416   creation of out-of-bounds pointer ('Integer' beyond end of data) by
      operator 'String'  -- An out-of-bounds pointer was created. See
      message 415 for a description of the parameters Integer and String.
      For example:

                int a[10];

                 ...

                f( a + 11 );

      Here, an illicit pointer value is created and is flagged as such by
      PC-lint/FlexeLint.  Note that the pointer a+10 is not considered by
      PC-lint/FlexeLint to be the creation of an out-of-bounds pointer. This
      is because ANSI C explicitly allows pointing just beyond an array. Access
      through a+10, however, as in *(a+10) or the more familiar a[10], would
      be considered erroneous but in that case message 415 would be issued.