Thread: Converting an unsigned int to to unsigned long long (64 bit)

Originally Posted by swoopy

>With gcc on my Windows XP box this works:
Thanks for the info Dave. Maybe I've got an old version of gcc. I'll try your exact code tomorrow with Dev-C++ and see what happens.

>(If you run gcc -pedantic, it mentions that ISO C90 does not support the 'll' printf modifier.)
I'll give that a try too, and see if that warning shows.

Well, I don't use dev-cpp for windows console apps and I hadn't tried it. (I use command line cygwin gcc for most things.)

Here's what I found about printing 64-bit ints with dev-cpp:

No need to "update". I doubt that it would change things. Format type specifiers can be found (the "right way") in <inttypes.h> (which includes <stdint.h>)

Here's something that runs on dev-cpp and other gnu gcc on my Windows XP box:

Code:

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

uint64_t make_longlong(uint32_t, uint32_t);

int main ()
{

  uint64_t start, end, diff;
  uint32_t hi, lo;


  hi = 0x12345678;
  lo = 0x9abcdef0;
  start = make_longlong(hi, lo);

  hi = 0x55555555;
  lo = 0x11111111;
  end = ((uint64_t)hi << 32) | lo;

  diff = end - start;

  printf("end   = %"PRIu64" (%"PRIx64" hex)\n",end, end);
  printf("start = %"PRIu64" (%"PRIx64" hex)\n",start, start);
  printf("diff  = %"PRIu64" (%"PRIx64" hex)\n",diff, diff);

  getchar();

  return 0;
}

/* if you want to make a function to hide the bit shifting 
 * here's a possibility
 */
uint64_t make_longlong(uint32_t hi, uint32_t lo)
{
  return ((uint64_t)hi << 32) | lo;
}

output is

Code:

end   = 6148914690091192593 (5555555511111111 hex)
start = 1311768467463790320 (123456789abcdef0 hex)
diff  = 4837146222627402273 (4320fedc76543221 hex)

Regards,

Dave

>Here's something that runs on dev-cpp and other gnu gcc on my Windows XP box:
Bingo, that works Dave. So the trick is to use the format specifier %"PRIu64".

Here's my question. Why does %llu work for you? You're running the same OS (Windows XP), and the same compiler as Dev-C++ uses. Is it something to do with cygwin?

By the way, I did go ahead and upgrade to Dev-C++, which looks like was worth it.

Well, maybe not the same compiler. cygwin gcc is probably more like the unix version. Would that be correct?

Originally Posted by swoopy

Well, maybe not the same compiler. cygwin gcc is probably more like the unix version. Would that be correct?

I don't have any insight into the differences. With the dev-cpp compiler, gcc --version gives this:

gcc (GCC) 3.3.1 (mingw special 20030804-1)

With cygwin's gcc I get this:

gcc (GCC) 3.3.3 (cygwin special)

I was thinking maybe different library versions.

In the <inttypes.h> for dev-cpp it says, for example:

Code:

#define PRIu64 "I64u"

In <inttypes.h> for cygwin, it says

Code:

#define PRIu64 "llu"

Anyhow, using the data types from <stdint.h> and format specifiers from <inttypes.h> we at least have portability among these two C compilers.

[edit]
Forgot to mention: My examples also work on my Linux Fedora 3 Box

gcc --version gives this:

gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)

And <inttypes.h> has stuff like this:

Code:

# if __WORDSIZE == 64
#  define __PRI64_PREFIX    "l"
#  define __PRIPTR_PREFIX    "l"
# else
#  define __PRI64_PREFIX    "ll"
#  define __PRIPTR_PREFIX
# endif


# define PRIu64        __PRI64_PREFIX "u"
# define PRIx64        __PRI64_PREFIX "x"

(The Linux version also works with %ll, obviously.)
[/edit]

Regards,

Dave