Re: How do I write directly to a memory address?

[Hyman Rosen <hyrosen@mail.com>]

On 2/11/2011 3:26 AM, Ludovic Brenta wrote:
> You are wrong because the C program can *also* overflow its stack or
> heap and you *also* have to worry about that, just like in Ada;

Actually, Ada has the more severe problem here, because Ada
makes it easy to declare objects on the stack which are sized
based on the values of subprogram parameters, while C and C++
do not. I know I've seen a good number of postings over the
years here on c.l.a. where newbies make this mistake - they'll
declare some local N�N�N matrix and wonder why their program
blows up. The heap is much more forgiving, especially nowadays.

> When looking at C code, if you don't constantly ask yourself "hat if
> the pointer is null, or the index is out of range?" then I am quite
> worried at the resulting quality of your code.

That just isn't so. Programs aren't just randomly tossed
together bits of code. When someone calls a function, they
know what the function expects and call it that way. It's
certainly possible to get things wrong, and it's true that
the result of such an error will be much more mysterious
than in Ada, but it is severely incorrect in C code to go
around looking at pointer indirections and adding checks
for null. It is simply the case that some routines expect
to be called with a non-null pointer, and in C it's the job
of the programmer to make sure that is what happens. You may
not like this way of working, but it is what it is, and you
are not going to convince any C programmer that the function
has bugs because it doesn't check. And similarly for array
bounds.

No one is asking you to abandon Ada for C, but as I said,
there are absolutely enormous amounts of correctly working
C code in existence, and you need to respect the language
and its practitioners enough to recognize that.

You might also ask yourself why, if Ada is so good, is it so
little used? There was the old canard that C programmers didn't
want their pointers and array bounds checked, but since the
world took so readily to Java, that doesn't hold water. Maybe
it's just that people don't respond well when told "We're going
to show you idiots how it *should* be done." It's interesting to
read J-P Rosen's <http://adalog.fr/publicat/Ada-paradox.pdf>.
It's full of this kind of attitude, that the designers of Ada
have cast pearls before swine.