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In article <40rjdn$jof@solutions.solon.com> seebs@solutions.solon.com
(Peter Seebach) writes:

|> It is undefined behavior to cast a float into an int, if the value contained
|> in that float is larger than INT_MAX, correct?

|> How are we to test this?  There exists (on at least one machine) at least
|> one float greater than INT_MAX which compares less than (float) INT_MAX;
|> in particular, on a 68000 system I use, INT_MAX is 2147483647, but
|> (float) INT_MAX is 2147483648.  So, 2147483647.5 would compare less
|> than INT_MAX, but would (in fact) be too large.

On the machine in question, of course, casting both values to double
should work.  This is *not* guaranteed, however.  (Consider a machine
with 64 bit int's and 64 bit double's, for example.)

|> I'm sure there exist machines where this disparity can be pushed further.

|> Can anyone suggest a *safe* way to test for this?

Portably, or non-portably.

I'm pretty sure that I could come up with a non-portable solution for
any given architecture, but I don't know of a portable (conforming)
way off hand.

|> On a related note, how can one determine the maximum number of digits one will
|> need to print an integer?  All modern programmers are, of course, making sure
|> that sprintf() destination strings have enough characters.  Is there
|> a portable way to define "enough characters"?

I generally just use ``sizeof( long ) * CHAR_BIT + 2''.  One character
per bit is enough for *any* base, and the +2 accounts for the sign and
the terminating '\0'.  Of course, in most cases, this is overkill.  If
you are calculating the size dynamically, then you could use
``(int)floor( log10( (double)( INT_MAX ) ) ) + 1'', or some such;
IMHO, this is just a waste of CPU time.

Another alternative would be to attact the problem from the other
side:

	assert( i < 1000 && i > -100) ;   /* Only 3 char's in target field */

Again, I can hardly think of an application where this would be useful.
-- 
James Kanze         Tel.: (+33) 88 14 49 00        email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
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