sprintf for unsigned _int64

Question

I am having following code. output of second %d in sprintf is always shown as zero. I think i am specifying wrong specifiers. Can any one help me in getting write string with right values. And this has to achieved in posix standard. Thanks for inputs

void main() {
    unsigned _int64 dbFileSize = 99;
    unsigned _int64 fileSize = 100;
    char buf[128];
    memset(buf, 0x00, 128);
    sprintf(buf, "\nOD DB File Size = %d bytes \t XML file size = %d bytes", fileSize, dbFileSize);
    printf("The string is %s ", buf);
    }

Output:

The string is
OD DB File Size = 100 bytes      XML file size = 0 bytes 

Answer 1

I don't know what POSIX has to say about this, but this is nicely handled by core C99:

#include <stdio.h>
#include <inttypes.h>

int main(void) {
    uint64_t dbFileSize = 99;
    uint64_t fileSize = 100;
    char buf[128];
    memset(buf, 0x00, 128);
    sprintf( buf, "\nOD DB File Size = %" PRIu64 " bytes \t"
                  " XML file size = %" PRIu64 " bytes\n"
                  , fileSize, dbFileSize );
    printf( "The string is %s\n", buf );
}

If your compiler isn't C99 compliant, get a different compiler. (Yes, I'm looking at you, Visual Studio.)

PS: If you are worried about portability, don't use %lld. That's for long long, but there are no guarantees that long long actually is the same as _int64 (POSIX) or int64_t (C99).

Edit: Mea culpa - I more or less brainlessly "search & replace"d the _int64 with int64_t without really looking at what I am doing. Thanks for the comments pointing out that it's uint64_t, not unsigned int64_t. Corrected.

Answer 2

You need to use %I64u with Visual C++.

However, on most C/C++ compiler, 64 bit integer is long long. Therefore, adopt to using long long and use %llu.

Answer 3

If you are looking for a portable solution, then use printf macros from <inttypes.h>. You may need to define __STDC_FORMAT_MACROS to make these available in C++.

Answer 4

I would use sprintf_s with %dz and uint64_t, and promptly discover that I'm an idiot when I try it and find that %dz, the format specifier for an unsigned int, will work for uint32_t, which is good news, but it won't work for uint64_t. While I think Keith Thompson has already answered this adequately with regards to using PRIu64, one change I would make would be to use the buffer overrun safe versions sprintf_s and printf_s, another would be to (direct) initialize the char when it is declared, as suggested by Jens Gustedt;

#include <stdio.h>
#include <inttypes.h>

uint64_t dbFileSize = 99;
uint64_t fileSize = 100;
char buf[128]{ 0 };
sprintf_s(buf, "\nOD DB File Size = %" PRIu64 " bytes \t XML file size = %" PRIu64 " bytes\n", fileSize, dbFileSize);
printf_s("The string is %s ", buf);