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Re: Null Pointer exceptions

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On Wed, 22 Apr 2015 21:34:25 +0000, jeff wrote:

> My question is: is there a way to deal with all of these problems in one 
> swoop, by ignoring all code that dereferences a null pointer, i.e. null 
> dereference becomes a NO-OP instead of triggering an exception. ?

In a sense, existing mechanisms already ignore "all code that dereferences
a null pointer", i.e. they terminate the process, resulting in the code
(i.e. the remainder of the program) being ignored. Maybe you meant to
suggest that it should ignore some smaller portion of the code? In which
case: which portion? How should the implementation determine that?

As for treating null dereference as a no-op: how can it? Pointer
dereference yields a value; what value should dereferencing a null pointer
yield? Just use whatever value happened to already be in the memory (or
register)? That's likely to just result in cascading failures; if the
value is itself a pointer, offset or index (or is used in the calculation
of such), you're going to end up accessing random memory locations.

And simply testing for a null pointer and conditionalising code which
depends upon the value obtained by dereferencing is often a workaround
rather than a fix. If null isn't a legitimate value, any fix would deal
with the reasons why the pointer was null, not the consequences.

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Null Pointer exceptions jeff <nospam@nospam.com> - 2015-04-22 21:34 +0000
  Re: Null Pointer exceptions James Kuyper <jameskuyper@verizon.net> - 2015-04-22 18:02 -0400
    Re: Null Pointer exceptions Stephen Sprunk <stephen@sprunk.org> - 2015-04-22 18:30 -0500
      Re: Null Pointer exceptions James Kuyper <jameskuyper@verizon.net> - 2015-04-22 19:44 -0400
        Re: Null Pointer exceptions Stephen Sprunk <stephen@sprunk.org> - 2015-04-23 11:53 -0500
          Re: Null Pointer exceptions Richard Heathfield <rjh@cpax.org.uk> - 2015-04-23 18:59 +0100
  Re: Null Pointer exceptions Barry Schwarz <schwarzb@dqel.com> - 2015-04-22 15:17 -0700
    Re: Null Pointer exceptions James Dow Allen <gmail@jamesdowallen.nospam> - 2015-04-23 04:11 +0000
  Re: Null Pointer exceptions Robert Wessel <robertwessel2@yahoo.com> - 2015-04-22 17:19 -0500
  Re: Null Pointer exceptions Ben Bacarisse <ben.lists@bsb.me.uk> - 2015-04-22 23:46 +0100
  Re: Null Pointer exceptions Nobody <nobody@nowhere.invalid> - 2015-04-23 03:14 +0100
    Re: Null Pointer exceptions James Kuyper <jameskuyper@verizon.net> - 2015-04-23 12:32 -0400

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