Re: [COFF] [TUHS] buffer overflow (Re: Happy birthday Morris worm - COFF

13 Nov 2019

On 2019-Nov-12 17:49:46 -0500, Arthur Krewat &lt;krewat(a)kilonet.net&gt; wrote:
...
 On 11/12/2019 5:41 PM, Robert Clausecker wrote:
> Oh please no.  One of the things we've hopefully all learned from Pascal
> is that length-prefixed strings suck because you can't perform anything
> useful without copying the entire string. 
Keep in mind that C doesn't have a "string" type.  The use of a NUL
terminated char array is purely convention.  There's nothing to stop
someone using a length-prefixed array (though there's virtually no
standard library support for that).

...
 > Rob Pike and friends showed
> how to get strings and vectors right in the Go language where you have a
> builtin slice type which is essentially a structure
>
>      struct slice(type) {
>              type *data;
>              size_t len, cap;
>      }; 
That approach would have incurred a 12-byte overhead for each string or
vector on a PDP-11 - that would have been a substantial disincentive on
a memory-constrained system.

...
 And none of that stops some programmer from doing
slice.cap=255 - or is 
it read-only? ;) 
Slices and strings are built-in types in Go.  They can be modelled as the
above structure but that is an implementation detail.  It is possible to
reduce the capacity of a slice (but not a string) but attempting to
increase it will result in a runtime exception ("panic" in Go speak).

-- 
Peter Jeremy