Re: Is this C style function well written and thread safe?
On Sep 13, 1:15 am, Pete Becker <p...@versatilecoding.com> wrote:
On 2007-09-12 18:44:38 -0400, Old Wolf <oldw...@inspire.net.nz> said:
On Sep 13, 4:08 am, "Ivan Vecerina"
<_INVALID_use_webfo...@ivan.vecerina.com> wrote:
<jeff_j_dun...@yahoo.com> wrote in message
: In the following function, pleas assume that the Date object is well
: written. What I really want to know is if my char buff is being
: handled safely.
: int iMonth=0, iDay=0, iYear=0;
: d.GetDate(iYear, iMonth, iDay);
: sprintf(buff, "%d/%d/%d", iMonth, iDay, iYear);
As you say, this is dreadful code because it will
buffer overflow if unexpected values comes from
GetDate.
But the explicit assumption is that GetDate is "well written,"
which certainly implies that it doesn't produce unexpected
values.
For what definition of "unexpected". I don't expect dates 10000
years in the future, but a well written GetDate routine might be
capable of generating them.
If it does, the problem is in GetDate, not in the code that
assumes that it does what it's supposed to do. If you don't
trust GetDate to meet its contract, what do you trust it to
do?
The problem here is that we don't know the contract of GetDate.
A priori, I would expect that the contract would restrict the
possible values for month and day, but would not do so for year;
it makes perfect sense to speak of the year 10000, or even of
the year 100000 (although one might not "expect" such values in
a particular application).
The more general problem is that we've been asked to evaluate
the correctness of a function without being told what the
contract for that function is. Which is an exercise in
futility. About all we can say is that "as it stands", the code
is completely broken, since if I pass it a null pointer, or a
buffer of length 2, bad things will happen, and there is nothing
anywhere which says that such arguments are not allowed.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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