strcmp实现

#include<stdio.h>
#include<assert.h>
int my_strcmp(const char*a,const char*b)
{
    while(*a&&*b&&*a==*b)
        a++,b++;
    if(*a&&*b)
        return(*a-*b);
    )
        ;
    &&*b)
        ;
    ;
}

int my_strcmp1(const char *str1, const char *str2)
{
     assert((str1 != NULL) && (str2 != NULL));
     ;
     while ( !(rt = *(unsigned char *)str1 - *(unsigned char*)str2 ) &&  *str2)
     {
         str1 ++;
         str2 ++;
     }
     )
     {
         rt = ;
     }
     )
     {
         rt = -;
     }
     return rt;
}  

int my_strcmp2(unsigned char *src, unsigned char *dst)
{
         ;
        while( ! (ret = *src - *dst) && *dst)
             ++src, ++dst;
         )
              ret = - ;
         )
              ret =  ;
        return( ret );
}

int my_strcmp3(const char *dest, const char *source)
{
   assert((NULL != dest) && (NULL != source));
   while (*dest && *source && (*dest == *source))
           {
                    dest ++;
                   source ++;
           }
   return *dest - *source;
}  

int my_strcmp4(const char* s1,const char * s2)
{
      for(;*s1==*s2;s1++,s2++)
        {
            if(*s1 == '\0')
                   ;
        }
      :);
}

int main()
{
    char *s1="abc",*s2="abcd";
    int m;
    m=my_strcmp4(s1,s2);
    printf("m=%d\n",m);
}

其它：

intstrcmp(p1,p2)

{

constchar*p1;

const char *p2;

{

registerconstunsignedchar*s1=(constunsignedchar*)p1;

registerconstunsignedchar*s2=(constunsignedchar*)p2;

unsignedreg_charc1,c2;

do{

c1=(unsignedchar)*s1++;

c2=(unsignedchar)*s2++;

if(c1=='\0')

returnc1-c2;

}while(c1==c2);

returnc1-c2;

}

libc_hidden_builtin_def(strcmp)