如何在运行时检查内存地址是否可写? [英] How can I check whether a memory address is writable or not at runtime?
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问题描述
如何在运行时检查内存地址是否可写?
How can I check whether a memory address is writable or not at runtime?
例如,我想在下面的代码中实现 is_writable_address.有可能吗?
For example, I want to implement is_writable_address in following code. Is it possible?
#include <stdio.h>
int is_writable_address(void *p) {
// TODO
}
void func(char *s) {
if (is_writable_address(s)) {
*s = 'x';
}
}
int main() {
char *s1 = "foo";
char s2[] = "bar";
func(s1);
func(s2);
printf("%s, %s
", s1, s2);
return 0;
}
推荐答案
我一般同意那些认为这是一个坏主意的人.
I generally concur with those suggesting that this is a bad idea.
也就是说,鉴于问题具有 UNIX 标记,在类 UNIX 操作系统上执行此操作的经典方法是使用来自的 read()
/dev/zero
:
That said, and given that the question has the UNIX tag, the classic way to do this on UNIX-like operating systems is to use a read()
from /dev/zero
:
#include <fcntl.h>
#include <unistd.h>
int is_writeable(void *p)
{
int fd = open("/dev/zero", O_RDONLY);
int writeable;
if (fd < 0)
return -1; /* Should not happen */
writeable = read(fd, p, 1) == 1;
close(fd);
return writeable;
}
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