英文:
How to prevent my code from the following conversion error?
问题
这可能听起来像一个XY问题，但我感到困惑。
我想在用户输入6时执行一些代码。首先看一下代码：
#include <stdio.h>
int main(void) {
short int x;
printf("Val :");
scanf("%d", &x);
if (x == 6) {
//一些代码
}
return 0;
}
在我的系统中，SHRT_MAX的值是32767，如果用户设法输入65442，它最终会被转换为6，然后在这个值上执行代码，尽管本应在6上执行。嗯，它确实在6上执行，但从用户的角度来看，这并不安全。是的，我可以使用int或long int，但如果用户破解short int，这并不是正确的选择。我该如何处理这个问题？
英文:
It may sound like an XY Problem but I am confused.
I want to execute some code when the user enters 6. First have a look at code:
#include<stdio.h>
int main(void) {
short int x;
printf("Val :");
scanf("%d", &x);
if (x == 6) {
//some code
}
return 0;
}
SHRT_MAX in my system is 32767 and if the user manages to enter 65442 this will be converted to 6 ultimately and the code will be executed at this value while it was supposed to execute at 6. Well, it is getting executed at 6 but from the user's point of view it is the lack of security. Yeah, I can use int or long int, but if the user is cracking short int, it is not the right choice. How can I deal with this issue?
答案1
得分: 7
> Re: SHRT_MAX in my system is 32767 and if user manages to enter 65442 this will be converted to 6
关于我的系统中的SHRT_MAX为32767，如果用户设法输入65442，则会转换为6。
From C11 7.21.6.2 The fscanf() function /10:
来自C11 7.21.6.2中的fscanf()函数/10：
> If this object does not have an appropriate type, or if the result of the conversion cannot be represented in the object, the behavior is undefined.
如果此对象没有适当的类型，或者转换的结果不能在对象中表示，行为是未定义的。
I suggest reading a whole line fgets() and parsing it with strtol(). scanf() is not suitable for this.
我建议读取整行使用fgets()，然后用strtol()进行解析。scanf()不适合此情况。
This might help: Correct usage of strtol().
这可能有所帮助：正确使用strtol()。
Sidenote: The %d format specifier expects an int *, not a short int *. Change it to %hd.
附注：%d格式说明符预期是一个int *，而不是一个short int *。将其更改为%hd。
英文:
> Re: SHRT_MAX in my system is 32767 and if user manages to enter 65442 this
> will be converted to 6
From C11 7.21.6.2 The fscanf() function /10:
> If this object does not have an appropriate type, or if the result of
> the conversion cannot be represented in the object, the behavior is
> undefined.
I suggest reading a whole line fgets() and parsing it with strtol(). scanf() is not suitable for this.
This might help: Correct usage of strtol().
Sidenote: The %d format specifier expects an int *, not a short int *. Change it to %hd.
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