Re: 128 bit integer


"Keith Thompson" <kst-u@xxxxxxx> wrote in message
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"BGB / cr88192" <cr88192@xxxxxxxxxxx> writes:
"Eric Sosman" <esosman@xxxxxxxxxxxxxxxxxxxx> wrote in message
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On 7/28/2010 7:34 AM, Lavanya Poondru wrote:
Hi all,

How to program 128 bit integer in C language ?

See Question 18.15d on the comp.lang.c Frequently Asked
Questions (FAQ) page at <http://www.c-faq.com/>.


also (will add this much):
some compilers add 128 bit (or more) integer types as an extension
feature,
but there is no real standardization here AFAIK.
[...]

Well, there's some.

An implementation that provides 128-bit integer types will probably
define int128_t, intleast128_t, and intfast128_t in <stdint.h>. All
these are optional, so even if long long is 128 bits an implementation
isn't *required* to define these typedefs (only the 8, 16, 32, and
64-bit "least" and "fast" typedefs are mandatory), but it would be silly
not to define them for 128 bits if the corresponding types exist.


forgot about stdint.h, I suspect partly because MSVC lacks this header...


And if any integer type is 128 bits or wider, intmax_t will be such a
type.

Repeat the above replacing "int" with "uint" for unsigned types.

But most current implementations, as far as I know, only support
integers up to 64 bits.


yeah, this is true of both MSVC and GCC AFAIK (actually, IIRC GCC supports
128 bit ints for certain targets, but I am not sure).

both my compiler and Mr. Navia's compiler support 128 bit ints (mine uses
the type name "__int128" internally).

I think also Open64 and a few others as well support them.

not really sure though, I haven't really looked into it much...



.

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