1.#include <stdio.h>
#include <assert.h>
size_t strlen(const char* s)
{
return ( assert(s), (*s ? (strlen(s+1) + 1) : 0) );
}
int main()
{
printf("%d
", strlen( NULL));
return 0;
}
2.#include <stdio.h>
#include <assert.h>
char* strcpy(char* dst, const char* src)
{
char* ret = dst;
assert(dst && src);//断言一定要调用assert，这是安全编程的思想，错误处理的思想
while( (*dst++ = *src++) != ' ' );
return ret;
}
int main()
{
char dst[20];
printf("%s
", strcpy(dst, "Delphi Tang!"));
getch();
return 0;
}
3.#include <stdio.h>
#include <malloc.h>
int main()
{
char s1[] = {'H', 'e', 'l', 'l', 'o'};
char s2[] = {'H', 'e', 'l', 'l', 'o', ' '};
char* s3 = "Hello"; //只读存储区
char* s4 = (char*)malloc(6*sizeof(char)); //堆
s4[0] = 'H';
s4[1] = 'e';
s4[2] = 'l';
s4[3] = 'l';
s4[4] = 'o';
s4[5] = ' ';
free(s4);
return 0;
}
4.#include <stdio.h>
#include <assert.h>
size_t strlen(const char* s)
{
size_t length = 0;
assert(s);
while( *s++ )
{
length++;
}
return length;
}
int main()
{
printf("%d
", strlen("123456789"));
return 0;
}