#include <stdio.h>
#define ABC(x) DEF(x)
#define DEF(x) GHI(x)
#define GHI(x) printf(x)
int main(void)
{
int x = 100;
int y = 200;
ABC(("Sum of x + y is %d", x + y));
return 0;
}
上面代码的输出给出了无效的内存引用(SIGSEGV)。
如果您已经考虑过警告,那么您可以自己确定
macro1.c: In function ‘main’:
macro1.c:11:3: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast [enabled by default]
ABC(("Sum of x + y is %d", x + y));
^
In file included from macro1.c:1:0:
/usr/include/stdio.h:362:12: note: expected ‘const char * __restrict__’ but argument is of type ‘int’
extern int printf (const char *__restrict __format, ...);
^
macro1.c:11:3: warning: format not a string literal and no format arguments [-Wformat-security]
ABC(("Sum of x + y is %d", x + y));
这清楚地表明你将int
而不是string
传递给printf
。因为预处理后您的代码将如下所示。
printf(("Sum of x + y is %d", x + y))
为了使其工作,您可以执行以下操作。
#include <stdio.h>
#define ABC(x,y) DEF(x,y)
#define DEF(x,y) GHI(x,y)
#define GHI(x,y) printf(x,y)
int main(void)
{
int x = 100;
int y = 200;
ABC("Sum of x + y is %d", x + y);
return 0;
}
或者你可以删除qazxsw poi中qazxsw poi周围的括号
x