Re: [Lit.] Buffer overruns

From: D. J. Bernstein (djb_at_cr.yp.to)
Date: 12/27/04

  • Next message: David Magda: "Re: are Unix and Netware mainstream enough" 
    Date: Mon, 27 Dec 2004 21:37:14 +0000 (UTC)

    Douglas A. Gwyn wrote:
    > None of that has anything to do with code that
    > obliviously tries to put more data into an object than
    > will fit into it, which is the topic of this thread.

    Resources are limited, Doug. There's always a risk of running out of
    space. That's life. What exactly should a program do when it runs out of
    space for storing something?

    Sribbling all over memory (or disk space)---for example, overwriting a
    return address---is obviously bad. What the program should do instead is
    raise an exception. Some applications handle the exception by trying
    again later; other applications inform another program, or a user, to
    try again later, or to give up if there's no hope.

    My sample program illustrates this. If it runs out of space, it notices,
    and it raises an exception (communicated through its exit code), exactly
    as it should. The basic point you keep missing is that C MAKES THIS
    UNNECESSARILY DIFFICULT. It's easier, in C, to scribble all over memory.
    I had to include an extra line of code in the program to make it behave
    properly; see the len comparison at the top of the inner loop?

    There are other programming environments that fix this ease-of-use
    problem. These programming environments make my good program easier to
    write---I don't need to bother with the len comparison!---while making a
    bad scribble-all-over-memory program much harder to write.

    ---D. J. Bernstein, Associate Professor, Department of Mathematics,
    Statistics, and Computer Science, University of Illinois at Chicago

  • Next message: David Magda: "Re: are Unix and Netware mainstream enough"

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