C语言中strcpy,strcmp,strlen,strcat函数原型

#include <stdio.h>
#include <assert.h>


char *strcpy(char *strDest, const char *strSrc) {
    char *address=strDest;
    assert((strDest!=NULL) &&  (strSrc!=NULL));
    while(*strSrc!='\0') {
        *strDest++=*strSrc++;
    }
    *strDest='\0';
    return address;
}

char *strcat(char *strDest, const char *strSrc) {
    char *address=strDest;
    assert((strDest!=NULL) &&  (strSrc!=NULL));
    while(*strDest!='\0') {
        strDest++;
    }
    while(*strSrc!='\0') {
        *strDest++ =* strSrc++;
    }
    *strDest='\0';
    return address;
}

nt strcmp(const char *str1,const char *str2) {
    assert((*str1!='\0' && *str2!='\0'));
    while (*str1 && *str2 && *str1==*str2) {
        str1++;
        str2++;
    }
    return *str1-*str2;
}

int new_strlen(const char *str) {
    assert(str != NULL);
    int len = 0;
    while (*str++ != '\0') {
        ++len;
    }
    return len;
}

void *memcpy(void *dst, void *src, size_t n) {
    char *dp = (char*)dst;
    char *sp = (char*)src;
    assert((src!=0) && (dst!=0) && n>0);
    while (n--) {
        *(dp++) = *(sp++);
    }
    *dp='\0';
    return dst;
}

void *new_memmove(void *dst, const void *src, int n) {
    char *dp = (char *)dst;
    char *sp = (char *)src;
    assert((src != 0)&&(dst != 0) && (n > 0));
    if (sp > dp || (sp+n) < dp) {
        while(n--)
            *(dp++)=*(sp++);
        *dp='\0';
    }else if (sp < dp){
        sp += n;
        dp += n;
        *dp = '\0';
        while(n--)
            *(--dp) = *(--sp);
    }
    return dst;
}

int main() {

    char dest[10];
    char* src = "test!";
    char* ret = strcpy(dest, src);
    printf("Test strcpy ret is :%s\n", ret);

    char cat1str[20] = "cat1";
    char* cat2str = "cat2";
    printf("Test strcat ret is :%s\n", strcat(cat1str, cat2str));

    char *len = "len";
    printf("Test strlen ret is :%d\n", new_strlen(len));

    char mem_dest[20];
    char* mem_src = "the src test memcpy";
    printf("Test memcpy ret is :%s\n", memcpy(mem_dest, mem_src, 10));

    char mv_dest[20];
    char* mv_src = "the src test memmove";
    printf("Test memmove ret is :%s\n", new_memmove(mv_dest, mv_src, 10));
}