Hi all,
Suppose I have:
#include <climits>
const int val = INT_MAX;
val += 1;
Does the standard prescribe what happens with the above overflowing?
And if not, is there any *portable* way of discovering what happens?
Note: I've tested in my platform and the value val wrapps around.
TIA, with my best regards,
G. Rodrigues 4 1218
Gonçalo Rodrigues <op*****@mail.t elepac.pt> writes: Hi all,
Suppose I have:
#include <climits>
const int val = INT_MAX; val += 1;
Does the standard prescribe what happens with the above overflowing? And if not, is there any *portable* way of discovering what happens?
Note: I've tested in my platform and the value val wrapps around.
Did you mean the const to be there? I get
Error 337: "foo.cc", line 5 # The left side of '+=' must be a modifiable lvalue.
val += 1;
^^^
Gonçalo Rodrigues schrieb: Hi all,
Suppose I have:
#include <climits>
const int val = INT_MAX; val += 1;
Does the standard prescribe what happens with the above overflowing? And if not, is there any *portable* way of discovering what happens?
Note: I've tested in my platform and the value val wrapps around.
undefined behaviour
the standard even mentions systems which raise exceptions on
overflow(like x86 does on division by zero).
* Gonçalo Rodrigues: Suppose I have:
#include <climits>
const int val = INT_MAX; val += 1;
Does the standard prescribe what happens with the above overflowing?
No.
It does however specify overflow behavior for unsigned integer types.
Where the value is reduced modulo 2^n, n the number of value representation
bits.
And if not, is there any *portable* way of discovering what happens?
Partially. std::numeric_li mits<int>::is_m odulo tells you whether the type
has wrapping behavior or not. However, if it doesn't (on nearly all modern
C++ implementation it will be wrapping, but _if_ it doesn't wrap) then that
still leaves the question of what happens on overflow, open.
Note: I've tested in my platform and the value val wrapps around.
Not very surprising; google for "two's complement".
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
On 9 Mar 2005 15:41:41 GMT, tp*@eng.cam.ac. uk (Tim Love) wrote: Gonçalo Rodrigues <op*****@mail.t elepac.pt> writes:
Hi all,
Suppose I have:
#include <climits>
const int val = INT_MAX; val += 1;
Does the standard prescribe what happens with the above overflowing? And if not, is there any *portable* way of discovering what happens?
Note: I've tested in my platform and the value val wrapps around. Did you mean the const to be there? I get
Error 337: "foo.cc", line 5 # The left side of '+=' must be a modifiable lvalue. val += 1; ^^^
Of course not, bad cut and paste.
Regards,
G. Rodrigues This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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