Re: CERT C Programming Language Secure Coding Standard

Army1987 wrote:
On Wed, 01 Aug 2007 18:31:49 -0400, Eric Sosman wrote:
Introduction/Rules Versus Recommendations, second point
in the definition of a rule:

There is an enumerable set of exceptional conditions
(or no such conditions) in which violating the coding
practice is necessary to ensure the correct behavior
for the program.

Perhaps my reading comprehension has deteriorated, but I can
make no sense of this sentence. The first part describes a
situation in which there is a set of conditions or there are
no conditions; isn't this vacuously true?
It means that that set is enumerable, i.e. that its cardinality
is aleph-null or less. (Since the empty set is enumerable, the
parenthesized phrase is redundant.) :-)
(More likely they meant that it is possible to enumerate all these
conditions, so it means that the set is finite, and perhaps
reasonably small. But if they meant *that* they'd better say "a
small set".)

Ah! I think I get it ("Light dawns on Marblehead"): It's
all right to flout the rules if the exceptional circumstances
that require flouting it are enumerable.

... but doesn't that mean that it's *always* all right to
flout the rules? The set of all possible Turing machines is
enumerable (by the diagonal argument), and the number of Turing
machines clearly dwarfs the number of programs that can actually
be written for real finite hardware, so ...?

Now that I (think I) understand the requirement, I am more
perplexed by it than when I thought it gibberish. That word
"enumerable" is, as you point out, at the root of the difficulty,
but what small finite number should be proposed? "It's OK to go
ape, but no more than forty-two times per MLOC?"

--
Eric Sosman
esosman@xxxxxxxxxxxxxxxxxxxx
.

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