Wireshark-dev: Re: [Wireshark-dev] [Wireshark-commits] rev 25171: /trunk/epan/dissectors/ /trun
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From: "Jeff Morriss" <jeff.morriss.ws@xxxxxxxxx>
Date: Fri, 25 Apr 2008 21:34:08 -0400


On Fri, Apr 25, 2008 at 7:49 PM, Luis EG Ontanon <luis@xxxxxxxxxxx> wrote:
On Fri, Apr 25, 2008 at 10:17 PM, Jeff Morriss
<jeff.morriss.ws@gmail.com> wrote:
>  Guy Harris wrote:
>  >       http://www.cs.berkeley.edu/~wychen/cs261/proposal.htm
>
>  If Figure 1 is really a problem then my understanding of C just went out
>  the window...



I wouldn't have got this by myself without the explanation  but if you
read the code as:

typedef unsigned short uid_t;

void dowork(uid_t u);
int main() {
   int x = read_from_network();
   // Squish root (it's not safe to   execute dowork() with uid 0)
   if ( (x & 0x0000ffff) == 0) exit(1);
   //       ^^^^^^^^^^^^^
   dowork(x);
}

you would have noticed the issue.

I get what he's saying but I just don't get it:  why would the compiler convert from int to unsigned short *before* it has to send the value into the call to dowork()?  E.g., 'x' should be an int until I (explicitly or implicitly) cast it to something else, non?  Actually it should still be an int after the call to dowork(); it just won't be an int when dowork() gets it.

Maybe I need to go back to school because I'm feeling very noobish right now.