Author: Vincent Diepeveen
Date: 11:38:11 06/07/04
Go up one level in this thread
On June 07, 2004 at 13:58:18, Robert Hyatt wrote:
>On June 07, 2004 at 13:13:33, Vincent Diepeveen wrote:
>
>>On June 07, 2004 at 10:40:09, Fabien Letouzey wrote:
>>
>>>On June 07, 2004 at 10:36:58, Vincent Diepeveen wrote:
>>>
>>>>On June 07, 2004 at 10:30:50, Fabien Letouzey wrote:
>>>
>>>>r = 1<<36; // works for good compilers not for the rest
>>>
>>>Hm, my understanding is that first "1<<36" should be calculated (so it's 0 if
>>>sizeof(int) <= 4) and *then* cast into r's type (oops, too late).
>>>Fabien.
>>
>>The result is undefined when integer = 32 bits and long long is 64 bits.
>>
>>Trivially it is a very natural thing to try to write r = 1 << 36 when using a 64
>>bits type;
>>
>>Needing to cast every non-integer is not a nice way of programming now that all
>>processors are getting 64 bits, and 99% of all programmers will make mistakes
>>with it, basically taking care C/C++ in the future is not a serious programming
>>language.
>>
>>Because ansi-C definitely runs behind here on good programming habits, it's up
>>to the compilers mercy whether it works or doesn't, so only good compilers will
>>support it, as they support a natural way of working with the environment.
>>
>>The rule in ansi-C should read that for constants assigned, they should be
>>assumed to have the same type and not that they should be assumed to be integer.
>
>
>That won't work. i = .1 * 20.0; would produce errors if you convert .1 and 20.0
>to integers first, then do the multiply.
>
>_NO_ compiler will think that 1 << 36 is anything but zero on an architecture
>where int == 32 bits. Making them do so would break more programs than it would
>help.
int = 32 bits in intel c++
unsigned _int64 is 64 bits in intel c++
i have no problems doing there:
unsigned _int64 a = 1 << 36;
>The ANSI C standard certainly has plenty of holes. But this really isn't one of
>them that is a problem...
it is a problem, because a while ago 'int' was 16 bits and only 'long' was 32
bits and if you used 'unsigned long' or 'long' you had to cast everywhere.
Now moving from 32 to 64 bits we see the same childish problems again.
If i say:
int a = 1 << 36;
this should be undefined when sizeof(int) = 4
however
int a = 1 << 36;
this should be working fine when sizeof(int) = 8
unsigned long long a = 1 << 36;
the above should be working *always* when sizeof(unsigned long long) >= 8.
By the way, why is microsoft net2003 not accepting
unsigned long long a=200;
printf("%llu\n",a);
It only works when:
printf("%I64u\n",a);
I am very pissed because of this already for quite a while, because my software
runs both *nix and windows.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.