Bug in switch statement ?

[narasimp]

Hi,

I have the following code:

func1()
{
  unsigned int i;
  int j = 3;
 
  switch(j)
  {
     case 3:
              i = -1UL;
              break;
      default:
              /*some operation*/
  }
 
  return(i);
}

The above code looks ok, compiles well without error and povides the output.

However, we have a tool which will compile c programs to see if there is any error in the code, maybe to identify mem leaks, dangling pointers etc.
When i use this tool to compile the above code, it says that we are READ_DANGLING at the return statement in the above code.

When I move the return statement inside case 1: after "i = -1UL", it doesn't show this error.

Assume that moving return inside or outside the switch does same operation.

Now my question:
1) why is it saying that we are doing a READ_DANGLING?
2) is there any scope w.r.t to variable returning within and outside switch
3) When i assign any other value to i other that -1UL, this issue is not seen. So is there any error with the way i am assigning the value to variable "i"??

Please help me in understanding the above.

--Thanks

[newb16]

@narasimp
Probably it interprets assigning negative number to unsigned as no-op, and is unable to propagate it (?) correctly out of switch statement.

[donbock]

I see two problems:

-1UL is appropriate for an unsigned long variable. It should be -1U for an unsigned int.

The value of i is returned. However, i is only initialized if the switch takes the case-3 path. Other paths are available. True, you've rigged your code so only the case-3 path is taken; but your static analyzer must be unimpressed.