bug1741.cpp

1     #include <stdio.h>
2
3     class A
4         {
5        public:
6         int len;            // length of array
7         int a[10];          // the array
8         A( int n = 0 )
9             {
10            if( n >= 10 ) n = 10;
11            for( int i = 0; i < n; i++ )
12                a[i] = 0,
13            len = n;
14            }
15        int get( int i ) const
16            { return i < len ? a[i] : 0; }
17        };
18
19    int main()
20        { A a; printf( "%d\n", a.get(10) ); return 0; }

The result of running this program printed the expected '0' using one compiler but produced a very large number using another. Why the difference? Hint: this will require a degree of visual acuity.

bug1741.cpp lint Output

--- Module:   bug1741.cpp
        _
        }
bug1741.cpp(14) : Info 1741: member 'A::len' (line 6) conceivably not initialized by constructor
        _
        }
bug1741.cpp(14) : Info 1741: member 'A::a' (line 7) conceivably not initialized by constructor

Reference Manual Explanation

 
1741  member  'Symbol' (Location) conceivably not initialized by constructor  -- The
      indicated member symbol may not have been initialized by a constructor.  Was this
      an oversight? There appears to be a path through a loop that does initialize the
      member and the warning is issued because it is not clear that the loop is always
      executed at least once.