调用ToString（）陷阱(Calling ToString() gotchas)

 这取决于你想用它做什么。 
 
 既然你在内存中有字符串，你可以通过小心你传递的参数来安全地避免缓冲区溢出。 例如，如果你正在扫描一个字符串，使用"%s" ，只需使用足够大的目标缓冲区来保存可能存在的最大字符串（并确保源缓冲区是一个有效的字符串，它是'\0'终止）。 
 
 所有*scanf()函数的一个危险是，如果您正在扫描一个数值，并且输入值太大而无法在目标类型中表示，则行为是未定义的。 例如，这个程序： 
 
#include <stdio.h>
int main(void) {
    const char *s = "999999999999999999999999999";
    int n;
    sscanf(s, "%d", &n);
    printf("n = %d\n", n);
    return 0;
}
 
 有未定义的行为（除非INT_MAX真的很大）。 
 
 您可以使用strto*()函数安全地扫描数值： strtol() ， strtoll() ， strtoul() ， strtoull() ， strtof() ， strtod() ， strtold() 。 他们对错误的行为有点棘手，但至少它是明确的。 

It depends on what you want to do with it.
 
Since you have the string in memory, you can safely avoid buffer overflows by being careful about the arguments you pass. For example, if you're scanning into a string, using "%s", just use a target buffer big enough to hold the biggest string that could possibly be there (and make sure that the source buffer is a valid string, i.e., that it's '\0'-terminated).
 
One danger of all the *scanf() functions is that if you're scanning a numeric value, and the input value is too big to be represented in the target type, the behavior is undefined. For example, this program:
 
#include <stdio.h>
int main(void) {
    const char *s = "999999999999999999999999999";
    int n;
    sscanf(s, "%d", &n);
    printf("n = %d\n", n);
    return 0;
}
 
has undefined behavior (unless INT_MAX is really really big).
 
You can safely scan numeric values using the strto*() functions: strtol(), strtoll(), strtoul(), strtoull(), strtof(), strtod(), strtold(). Their behavior on errors is a bit tricky, but at least it's well defined.