Literal types: 0x1ull vs 0x1llu

Question

My gcc compiler allows me to define an unsigned long long (i.e. 64-bit) literal as

#define A_LITERAL 0x1ull

--- or ---

#define A_LITERAL 0x1llu

Is there any difference between these two literal statements. Is this common to other C compilers?

I'm voting this up since it taught me something. I already _knew_ both forms were valid but preferred `ULL` because it matched the `unsigned long long` type. However, it turns out the types are pretty fluid as well, allowing such "weirdness" as `long unsigned long`: see http://stackoverflow.com/questions/17287957/is-long-unsigned-as-valid-as-unsigned-long-in-c — paxdiablo, Jun 25 '13 at 02:03

score 6 · Answer 1 · edited Jun 25 '13 at 01:27

6

Both are the same: excerpt from n3337 draft of C++11 standard:

integer-suffix:
    unsigned-suffix long-suffix(opt)
    unsigned-suffix long-long-suffix(opt)
    long-suffix unsigned-suffix(opt)
    long-long-suffix unsigned-suffix(opt)

unsigned-suffix: one of
    u U

long-suffix: one of
    l L

long-long-suffix: one of
    ll LL

edited Jun 25 '13 at 01:27

paxdiablo

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answered Jun 25 '13 at 01:26

Mats Petersson

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Cleaned up the optional indicators to make them stand out (were subscripted in the standard). – paxdiablo Jun 25 '13 at 01:28
Thanks. I was hoping my "paste" from the document would translate a little better than it did... – Mats Petersson Jun 25 '13 at 01:30
This isn't a C++ question. – Potatoswatter Jun 25 '13 at 03:31

score 3 · Accepted Answer · answered Jun 25 '13 at 01:26

3

Both are allowed by the C standard (section 6.4.4.1).

The unsigned suffix u can be before or after the long l (or long long (ll)) suffix.

answered Jun 25 '13 at 01:26

Some programmer dude

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Marking this the answer as the question was in the context of C and this quotes the C standard. – Benjamin Leinweber Jun 25 '13 at 03:31

haccks · Answer 3 · 2013-06-30T18:34:00.917

0

ull or llu force the compiler to treat a constant as an unsigned and long long integer.
The order of ll and u doesn't matter, nor their case. you may also write LLU or ULL.

edited Jun 30 '13 at 18:34

answered Jun 25 '13 at 01:32

haccks

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Literal types: 0x1ull vs 0x1llu

3 Answers3

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