Re: SInt64 and UInt64 problems with large values

FROM : Segher Boessenkool
DATE : Mon Apr 04 10:45:26 2005

>> In lieu of using "long long" and "unsigned long long" in my code, I'm
>> trying to use the more compact "SInt64" and "UInt64" both of which
>> the compiler seems to be aware of , but when I try to give UInt64 a
>> large constant hex value such as 0xFFFFFFFFFFFFFFFF, the complier
>> complains that "integer constant is too large for "long" type." I
>> searched for the definition of UInt64 and found it in MacTypes.h
>> where it is defined as "typedef unsigned long long UInt64" so why
>> does the compiler not allow the maximum hex value? Is there some
>> undocumented upper limit to long long values?

>
> Check the compiler support for big constants. By default, these
> constants are integers (the compiler, at the time the constant is
> interepreted, does not and cannot know you will store it into a long
> or even long long), and thus self-evidently too big.


Of course it is an integer -- although I think you meant 'int'.

GCC is by default in C90 mode; integer constants of higher precision
than 'long' need a suffix then -- they do not in C99 mode.

> You'll have to use some suffix, like 0xFF...FFull (or something), to
> let the compiler know the constant is long long AND unsigned, too. At
> the moment, I don't recall the proper suffix though, sorry.


You remembered correctly, it is 'ull' (or 'ULL' or 'llU' or...).
For hexadecimal constants, you do not need to specify the 'U' though,
just the 'LL' is enough.


Segher