Poxy old computers (was RE: [extropy-chat] SPACE: Spirit Prob lems)
mail at HarveyNewstrom.com
Tue Feb 3 01:21:54 UTC 2004
On Monday, February 2, 2004, at 05:50 pm, Emlyn O'regan wrote:
> Adrian wrote:
>> including the
>> "nevers" such as strcpy instead of strncpy (or, at
>> least, strcpy into a buffer that could be smaller than
> You can fix a lot of these kinds of problems, also, by only writing in
> when there is absolutely no alternative. Which is really rather seldom.
Actually, this is not true. Other computer languages have the same
basic computer problems as C, usually. They just hide them from the
user. For example, C has pointers that tell you where a string starts.
If a pointer is null or points to the wrong spot, you can have a
problem. Java doesn't have pointers defined in the language. Most
people believe that Java therefore doesn't have pointers in the
programs. Not so! The Java compiler does indeed use pointers, just as
all machine-language compiled code does. It just does not provide any
language equivalent to discuss them or utilize them. Java programs can
still crash with a null-pointer error, which confuses Java people who
think it has no pointers.
Another example: In C, a string of characters is an array of
characters. So the variable NAME_ONE is really a pointer to a series
of characters. In C, if you set NAME_TWO to equal NAME_ONE, only the
pointer is copied. Both variables point to the same sequence in
memory. Thus, any changes to NAME_ONE magically appear changed in
NAME_TWO, because they really are overlapping memory spaces. Guess
what? Java does the same thing. Only without the pointers, it isn't
clear. Declare a Java string called NAME_ONE. Declare another
variable called NAME_TWO and set it equal to NAME_ONE. Suprisingly,
any change to one variable appears in the other. Many Java programmers
don't know this, because they don't know how the underlying pointers
and structures are being used.
It is not clear to me if Java fixes the problems of C, or just hides
them so they are harder to see.
Harvey Newstrom, CISSP, CISA, CISM, IAM, IBMCP, GSEC
Certified IS Security Pro, Certified IS Auditor, Certified InfoSec
NSA Certified Assessor, IBM Certified Consultant, SANS Certified GIAC
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