How to specify 64 bit integers in c

Question

I'm trying to use 64 bit integers in C, but am getting mixed signals as to whether it should be possible.

When I execute the printf:

printf("Size of long int:%d\nSize of long long int:%d\n\n",(int)sizeof(long int), (int)sizeof(long long int)); 

The response I get is:

Size of long int:4 Size of long long int:8

This makes me feel that a long long int has 8 bytes = 64 bits.

However, when I try to declare the following variables:

long long int a2 = 0x00004444; long long int b2 = 0x000044440; long long int c2 = 0x0000444400; long long int d2 = 0x00004444000; long long int e2 = 0x000044440000; long long int f2 = 0x0000444400004; long long int g2 = 0x00004444000044; long long int h2 = 0x000044440000444; long long int i2 = 0x0000444400004444; 

The last 4 variables (f2,g2,h2,i2) give me the error message:

warning: integer constant is too large for ‘long’ type

I get the same result when I replace 'long long int' with 'int64_t'. I assume 'int64_t' was recognized, since it didn't generate any error messages of its own.

So, it appears my 8 byte long long int is really a 6 byte long long int, and I don't understand what I'm missing here. If it's any help, here is the information on my gcc compiler:

me@ubuntu:~$ gcc -v   Using built-in specs.   Target: i686-linux-gnu   Configured with: ../src/configure -v    --with-pkgversion='Ubuntu/Linaro 4.4.4-14ubuntu5'   --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs    --enable-languages=c,c++,fortran,objc,obj-c++   --prefix=/usr    --program-suffix=-4.4    --enable-shared    --enable-multiarch    --enable-linker-build-id    --with-system-zlib    --libexecdir=/usr/lib    --without-included-gettext    --enable-threads=posix    --with-gxx-include-dir=/usr/include/c++/4.4    --libdir=/usr/lib    --enable-nls    --with-sysroot=/ -   -enable-clocale=gnu    --enable-libstdcxx-debug    --enable-objc-gc    --enable-targets=all  --disable-werror    --with-arch-32=i686    --with-tune=generic    --enable-checking=release    --build=i686-linux-gnu    --host=i686-linux-gnu    --target=i686-linux-gnu   Thread model: posix   gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5)    

If anyone knows how (or if) 64 bit integers are accessible to me, I'd really appreciate any help. Thanks....

Answer 1

Use stdint.h for specific sizes of integer data types, and also use appropriate suffixes for integer literal constants, e.g.:

#include <stdint.h>  int64_t i2 = 0x0000444400004444LL;