printf format for unsigned __int64 on Windows

Question

I need to print a ULONGLONG value (unsigned __int64). What format should i use in printf ? I found %llu in another question but they say it is for linux only.

Thanks for your help.

Funchal

Can you use std::cout? It should just work. – Acuminate

I can't. The function i use is a wrapper with variable argument list that uses printf and which i can't modify. – Funchal

Read this also: A funny thing with sprintf – Brenda

%llu is not for Linux only; it's the format defined by the ISO C standard, starting with the 1999 edition. Unfortunately, Microsoft's C implementation doesn't support C99 or later. In other words, it's Windows, not Linux, that's the special case. – Haskel

Answer 1

Using Google to search for “Visual Studio printf unsigned __int64” produces this page as the first result, which says you can use the prefix I64, so the format specifier would be %I64u.

Farmelo

Other choice is macro PRIu64 defined in inttypes.h – Brenda

@GrijeshChauhan: PRIu64 and inttypes.h are not supported in Visual Studio (at least, not by Microsoft). – Farmelo

Be aware that both __int64 and %I64u are specific to Visual Studio, so your code will not be portable to any other implementation. – Haskel

It's not in the plans :P – Funchal

Actually... using Google to search for "Visual Studio printf unsigned __int64" produces THIS page as the first result. Maybe remove the Google-shaming to future-proof your answer? – Doall

Answer 2

%llu is the standard way to print unsigned long long, it's not just for Linux, it's actually in C99. So the problem is actually to use a C99-compatible compiler, i.e, not Visual Studio.

C99 7.19.6 Formatted input/output functions

ll(ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a long long int or unsigned long long int argument; or that a following n conversion specifier applies to a pointer to along long int argument.

Excoriation

I wouldn't bother with this if i could choose what software i'm working with. – Funchal

Unfortunately, Microsoft does not define a ULONGLONG to be an unsigned long long. Per this page, it is an unsigned __int64. Using a format for unsigned long long might or might not work, but, if you want your code to survive compiler updates and future migrations, you should stick to the specification of the type. – Farmelo

@Funchal Your question says you need to use it in Windows, not saying Visual Studio. – Excoriation

@YuHao: ULONGLONG and __int64 are types in Visual Studio. – Farmelo

@EricPostpischil didn't know that, sorry about that. But I think it's still worth pointing out %llu is not Linux only. It is Microsoft's fault not to follow C99. – Excoriation

@YuHao It is not a fault. It is by design decision. Microsoft Visual C++ is not a C but C++ compiler which supports as much C standard(s) as C++98|03|11|14|17|... require – Phonemics

@Phonemics that is absolutely incorrect. Msvc supports e.g. naming variables new and private which goes far beyond what C++ requires – Eyebrow

@AnttiHaapala "we don't say much about later C standards conformance, and this is intentional. MSVC includes a C89/C90 compliant compile (...) Support for later C standards is limited to the subset required by the C++ standard." github.com/MicrosoftDocs/cpp-docs/issues/… – Phonemics

%lld also worked for me although I think %llu is better – Elatia

@Phonemics C++11 1.1 Scope, paragraph 2 (bolding mine): "C++ is a general purpose programming language based on the C programming language as described in ISO/IEC 9899:1999 Programming languages" A standard-conforming C++11 implementation must therefore provide C99's %ll format modifier via cstdio and therefore the [unsigned] long long types. Any Microsoft implementation of C++11 that does not provide [unsigned] long long does not comply with the C++ standard. – Cambria

Answer 3

I recommend you use PRIu64 format specified from a standard C library. It was designed to provide users with a format specifier for unsigned 64-bit integer across different architectures.

Here is an example (in C, not C++):

#include <stdint.h>   /* For uint64_t */
#include <inttypes.h> /* For PRIu64 */
#include <stdio.h>    /* For printf */
#include <stdlib.h>   /* For exit status */

int main()
{
    uint64_t n = 1986;
    printf("And the winning number is.... %" PRIu64 "!\n", n);
    return EXIT_SUCCESS;
}

Drawn

Visual Studio does not support stdint.h or inttypes.h. It does not support C 1999. There are third-party implementations of them. – Farmelo

@EricPostpischil: Have guys at Microsoft completely lost their minds? :( – Drawn

Thanks for your help, but %I64d does the job. – Funchal

@EricPostpischil Fwiw, Visual Studio began stdint.h support with VS2010 (is use it regularly).But they still missed the bus on C99 (and from what I read, they not even bothering with it). Ugh. – Sham

@WhozCraig: Does it support inttypes.h too? – Farmelo

@EricPostpischil Not that i've seen, as evidenced by numerous wailings a gnashing of teeth from VS2010 articles across this great web of ours. – Sham

@VladLazarenko: Microsoft is more interested in making money than in conforming to ISO standards. Apparently they've decided, so far, that C99 support is not worth the investment that would be required. I don't like it either (it slows general adoption of C99, to say nothing of C11), but I'm not in a position to judge whether their decision is correct in the context in which they've made it. They're under no obligation to support C99 -- or to support C at all, for that matter. (How many C compilers have you written?) – Haskel

@KeithThompson: Totally agree with you on this one. Microsoft does not own us anything. I just wish that a company with such a resource and influence would do more good for the society and programmers in general. So far they just create inconsistencies :) – Drawn

@VladLazarenko: They have said that they'll add at least some C99 support in the next release of Visual Studio. – Haskel

Answer 4

Printf has different format specifiers for unsigned long long depending on the compiler, I have seen %llu and %Lu. In general I would advice you to use std::cout and similar instead.

Yoshieyoshiko

The question is tagged both "c" and "c++". In C, std::cout is nothing more than a syntax error. – Haskel

Answer 5

Here is a work around for HEX output

printf("%08X%08X", static_cast<UINT32>((u64>>32)&0xFFFFFFFF), static_cast<UINT32>(u64)&0xFFFFFFFF));

Acuminate

Answer 6

For guys who forget all the time like me,
If you use Visual Studio (choosing MSVC compiler, to be specific),

%I64u for uint64_t == unsigned __int64 == unsigned long long

%I64d for int64_t == __int64 == long long

%Iu for size_t (==unsigned __int64 in win64, else unsigned int)

You should check this MSDN for the details, or just this section :)
also, if interested, other MSDNs like this and this.

_{# C++ Windows format string MSVC Visual Studio size_t int64_t uint64_t}

Cleo