bug809.cpp

1    #include <stdio.h>
2    #include <string.h>
3    enum type { H=1 /* herbivore */, C=2 /* carnivore */,
4                S=4 /* sweet tooth */, D=8 /* Drinker */ };
5    //lint -e655 -e641  inhibit warnings about using enum's as integers
6    char *dish( int x )
7        {
8        char buf[100]; char *p = buf; *p = 0;
9        if( x & D ) strcat( p, "rum-soaked " );
10       if( x & S ) strcat( p, "sugared " );
11       if( x & C ) strcat( p, "turkey " );
12       if( x & H ) strcat( p, "broccoli " );
13       return p;
14    }
15   int main()
16       {
17       printf( "please pass the %s and the %s.",
18           dish(C|S), dish(H|D) );
19       return 0;
20       }

Our cook decided to automate Thanksgiving dinner by running this little program to take into account the eccentricities of our guests. But something is going quite wrong. What is it?

bug809.cpp lint Output

--- Module: bug809.cpp
        _
return p;
bug809.cpp(13) : Info 809: Possible return of address of auto through variable 'p'

Reference Manual Explanation

809   Possible return of address of auto through variable 'Symbol'  -- The value
      held by a pointer variable may have been the address of an auto variable.  
      It is normally incorrect to return the address of an item on the stack because 
      the portion of the stack allocated to the returning function is subject to 
      being obliterated after return.