您所在位置：主题：[转帖]用程序证明 NULL '\0' 0 的不同
antigloss
[专家分：1700] 发布于 2005-09-17 11:28:00
编译以下程序，你将得到编译器的警告
/* test.c */
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int i = 5;
int* ptr = malloc(1);
char ch = 'e';
/* Checking an int vs the other two */
if ( i == NULL)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( i == '\0')
puts ("This shouldn't happen");
else
puts ("But this should");
/* Checking a ptr vs the other two */
if ( ptr == 0)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( ptr == '\0')
puts ("This shouldn't happen");
else
puts ("But this should");
/* Checking a character vs the other two */
if ( ch == NULL)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( ch == 0)
puts ("This shouldn't happen");
else
puts ("But this should");
free(ptr);
getchar();
return 0;
}
==========================================
test.c: In function `main':
test.c:10: warning: comparison between pointer and integer
test.c:28: warning: comparison between pointer and integer
我用的是 Dev-C++
可以在这里下载 http://free3.e-168.cn/antigloss/blog.php?do_showone/tid_42.html
此外，大家也可以参考这个网站 http://www.eskimo.com/~scs/C-faq/s5.html
/* test.c */
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int i = 5;
int* ptr = malloc(1);
char ch = 'e';
/* Checking an int vs the other two */
if ( i == NULL)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( i == '\0')
puts ("This shouldn't happen");
else
puts ("But this should");
/* Checking a ptr vs the other two */
if ( ptr == 0)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( ptr == '\0')
puts ("This shouldn't happen");
else
puts ("But this should");
/* Checking a character vs the other two */
if ( ch == NULL)
puts ("This shouldn't happen");
else
puts ("But this should");
if ( ch == 0)
puts ("This shouldn't happen");
else
puts ("But this should");
free(ptr);
getchar();
return 0;
}
==========================================
test.c: In function `main':
test.c:10: warning: comparison between pointer and integer
test.c:28: warning: comparison between pointer and integer
我用的是 Dev-C++
可以在这里下载 http://free3.e-168.cn/antigloss/blog.php?do_showone/tid_42.html
此外，大家也可以参考这个网站 http://www.eskimo.com/~scs/C-faq/s5.html
