c - 使用 snprintf 避免缓冲区溢出

Question

I dont understand why I am getting an output like this: StackOver↨< as snprintf should take care of null termination as expected output is StackOver. I am using devcpp IDE.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

int main(void)
{
    char buffer[10];
    printf("%d\n", sizeof(buffer));
    snprintf(buffer, sizeof(buffer), "%s", "StackOverflow");
    printf("%s", buffer);
    return 0;
}

Answer 1

C Standard states复制的字符串应以 nul 结尾:

7.21.6.5 The snprintf function

...

Description

The snprintf function is equivalent to fprintf , except that the output is written into an array (specified by argument s ) rather than to a stream. If n is zero, nothing is written, and s may be a null pointer. Otherwise, output characters beyond the n-1st are discarded rather than being written to the array, and a null character is written at the end of the characters actually written into the array. If copying takes place between objects that overlap, the behavior is undefined.

看来您正在使用过时的和/或错误的 C 运行时库运行，因为 snprintf() 实现似乎没有正确实现所需的行为。