Forum: Ruby checking if machine is 64-bit

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Suraj K. (Guest)
on 2007-07-28 21:42
Hello,

I am checking if the machine is 64-bit by doing this:

  require 'rbconfig'
  is_machine_64_bit = ( Config::CONFIG["arch"] =~ /64/ )

Is there a better way?

Thanks.
Michael F. (Guest)
on 2007-07-28 23:04
(Received via mailing list)
On 7/29/07, Suraj K. <removed_email_address@domain.invalid> wrote:
> Hello,
>
> I am checking if the machine is 64-bit by doing this:
>
>   require 'rbconfig'
>   is_machine_64_bit = ( Config::CONFIG["arch"] =~ /64/ )

Config::CONFIG['arch']
# "x86_64-linux"

> Is there a better way?

Not that i know of.

^ manveru
Daniel B. (Guest)
on 2007-07-28 23:52
(Received via mailing list)
On Jul 28, 11:42 am, Suraj K. <removed_email_address@domain.invalid> wrote:
> Hello,
>
> I am checking if the machine is 64-bit by doing this:
>
>   require 'rbconfig'
>   is_machine_64_bit = ( Config::CONFIG["arch"] =~ /64/ )
>
> Is there a better way?

if (2**33).kind_of?(Bignum)
   # 32 bit
else
   # 64 bit
end

Might need some tweaking once the 128 bit operating systems show up...

Regards,

Dan
Suraj K. (Guest)
on 2007-07-29 02:31
Daniel B. wrote:
> if (2**33).kind_of?(Bignum)
>    # 32 bit
> else
>    # 64 bit
> end

Excellent idea.  However, note that it takes 34 bits to represent 2**33,
and 33 bits to represent 2**32. Thus, we can get away with only checking
whether 2**32 is a Fixnum:

  is_machine_64_bit = (2 ** 32).is_a? Fixnum
Suraj K. (Guest)
on 2007-07-29 02:40
Suraj K. wrote:
>   is_machine_64_bit = (2 ** 32).is_a? Fixnum

Hmm, after reading the ri manpage for Fixnum, I found a better way:

  (-1.size) is 4 on a 32-bit machine and 8 on a 64-bit machine.
Xeno C. (Guest)
on 2007-07-29 02:52
(Received via mailing list)
Suraj K. wrote:
> Suraj K. wrote:
>>   is_machine_64_bit = (2 ** 32).is_a? Fixnum
>
> Hmm, after reading the ri manpage for Fixnum, I found a better way:
>
>   (-1.size) is 4 on a 32-bit machine and 8 on a 64-bit machine.
Aren't you gonna get Kernel information for 32 bit if it's a 32 bit
Kernel on a 64 bit machine?
Lionel B. (Guest)
on 2007-07-29 02:58
(Received via mailing list)
Suraj K. wrote:
> Suraj K. wrote:
>
>>   is_machine_64_bit = (2 ** 32).is_a? Fixnum
>>
>
> Hmm, after reading the ri manpage for Fixnum, I found a better way:
>
>   (-1.size) is 4 on a 32-bit machine and 8 on a 64-bit machine.
>

I don't know if it matters to you, but IIRC there are architectures with
different sizes for integers and memory addresses (64 bit integers with
32 bit addresses if memory serves).

Lionel.
Logan C. (Guest)
on 2007-07-29 03:31
(Received via mailing list)
On 7/28/07, Lionel B. <removed_email_address@domain.invalid> wrote:
> >
>
> I don't know if it matters to you, but IIRC there are architectures with
> different sizes for integers and memory addresses (64 bit integers with
> 32 bit addresses if memory serves).


MRI needs sizeof(long) == sizeof(void *)  (or it won't compile). MRI
Fixnums
are longs.

Lionel.
Nobuyoshi N. (Guest)
on 2007-07-29 03:39
(Received via mailing list)
Hi,

At Sun, 29 Jul 2007 02:42:46 +0900,
Suraj K. wrote in [ruby-talk:262297]:
> I am checking if the machine is 64-bit by doing this:
>
>   require 'rbconfig'
>   is_machine_64_bit = ( Config::CONFIG["arch"] =~ /64/ )
>
> Is there a better way?

Depends on the purpose.

If you are trying to compile an extension library:

  is_machine_64_bit = check_sizeof("int") == 64

  is_machine_64_bit = try_static_assert("sizeof int == 64")

or, better in C source(s):

  #if SIZEOF_VOIDP == 8

Otherwise, if you want to know the current running platform is
64bit:

  is_machine_64_bit = [0].pack("i!").size == 8

Note that all of the above check for the size of int.
Lloyd L. (Guest)
on 2007-07-30 16:53
Suraj K. wrote:
>   (-1.size) is 4 on a 32-bit machine and 8 on a 64-bit machine.

Very slick!  Nice find!
M. Edward (Ed) Borasky (Guest)
on 2007-07-30 17:21
(Received via mailing list)
Lloyd L. wrote:
> Suraj K. wrote:
>>   (-1.size) is 4 on a 32-bit machine and 8 on a 64-bit machine.
>
> Very slick!  Nice find!
>

Is that portable to jRuby??
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