Problem with structure size of sysinfo

To get the result of sysinfo by syscall in fasm, I have to declare memory size for storing the information. However, the size of the structure seems not match what Linux declared in kernel.h...

So, I use gcc (v4.1.0) to confirm the size of the structure...

Please compare the following 3 structures... (Fedora Code 5, x86_64)

Code:

#include <iostream>

using namespace std;

struct sysinfo {
        long uptime;            /* Seconds since boot */
        unsigned long loads[3]; /* 1, 5, and 15 minute load averages */
        unsigned long totalram; /* Total usable main memory size */
        unsigned long freeram;  /* Available memory size */
        unsigned long sharedram;/* Amount of shared memory */
        unsigned long bufferram;/* Memory used by buffers */
        unsigned long totalswap;/* Total swap space size */
        unsigned long freeswap; /* swap space still available */
        unsigned short procs;   /* Number of current processes */
        unsigned short pad;     /* explicit padding for m68k */
        unsigned long totalhigh;/* Total high memory size */
        unsigned long freehigh; /* Available high memory size */
        unsigned int mem_unit;  /* Memory unit size in bytes */
        char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
};

struct sysinfo_2 {
        unsigned short procs;   /* Number of current processes */
        unsigned short pad;     /* explicit padding for m68k */
};

struct sysinfo_3 {
        unsigned long freeswap; /* swap space still available */
        unsigned short procs;   /* Number of current processes */
        unsigned short pad;     /* explicit padding for m68k */
};

int main()
{
        cout << "Size of char      = " << sizeof(char) << endl;
        cout << "Size of short     = " << sizeof(short) << endl;
        cout << "Size of int       = " << sizeof(int) << endl;
        cout << "Size of long      = " << sizeof(long) << endl;
        cout << "Size of double    = " << sizeof(double) << endl;
        cout << "Size of sysinfo   = " << sizeof(sysinfo) << endl;
        cout << "Size of sysinfo_2 = " << sizeof(sysinfo_2) << endl;
        cout << "Size of sysinfo_3 = " << sizeof(sysinfo_3) << endl;

        exit(0);
}

and result is...

Code:

Size of char      = 1
Size of short     = 2
Size of int       = 4
Size of long      = 8
Size of double    = 8
Size of sysinfo   = 112
Size of sysinfo_2 = 4
Size of sysinfo_3 = 16

the size of sysinfo should be 104 instead of 112, the size of sysinfo_2 is correct and the size of sysinfo_3 should be 12 instead of 16...

anyone knows what's going on ?? gcc bug?

Thanks a lot !!