程序代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct In
{
    int data;
    char str[100];
};

int In_Compare( const void* a, const void* b )
{
    struct In* pa = (struct In*)a;
    struct In* pb = (struct In*)b;

    int v = strcmp(pa->str,pb->str);
    if( v != 0 )
        return v;

    if( pa->data < pb->data ) return -1;
    if( pa->data > pb->data ) return +1;
    return 0;
}

int main( void )
{
    struct In s[] = { {2,"b"}, {1,"b"}, {3,"a"} };
    qsort( s, sizeof(s)/sizeof(*s), sizeof(*s), &In_Compare );

    for( size_t i=0; i!=sizeof(s)/sizeof(*s); ++i )
        printf( "%s --- %d\n", s[i].str, s[i].data );

    return 0;
}