[英]“Stack smashing detected” when concatenating strings in C
I used this code to concatenate two strings in C: 我使用此代码在C中串联了两个字符串:
int main(int argc, char** argv) {
char a[] = "hello ";
char b[] = "world";
concat(a, b);
printf("%s\n", a);
return (EXIT_SUCCESS);
}
void concat(char s[], char t[]){
int i, j;
i = j = 0;
while (s[i] != '\0') i++;
while ((s[i++]=t[j++]) != '\0');
}
The string was concatenated correctly but the next line in output was: 字符串已正确连接,但输出的下一行是:
*** stack smashing detected *** [...] terminated
Why was this code detected as stack smashing? 为什么将此代码检测为堆栈破坏?
char a[] = "hello ";
This declares a char
array with exactly 7 elements, the six characters plus \\0
. 这将声明一个恰好具有7个元素的
char
数组,六个字符加\\0
。 There's no room for anything to be concatenated. 没有任何空间可以串联。
A simple fix is to reserve more space, if you know how much data you want to add. 一个简单的解决方法是保留更多空间,如果您知道要添加多少数据。
char a[12] = "hello ";
Strings in C are set length, thus you can't append something to them. C中的字符串是设置长度的,因此您不能在其中附加任何内容。 You have to create a new one and copy both to it.
您必须创建一个新的并将其复制到其中。 The error is triggered because you are writing to a space that wasn't allocated to you.
因为您正在写入未分配给您的空间,所以触发了错误。 You got only 7 bytes, but you are writing 8th, 9th... 12th byte, thus owerwriting other program data (smashing the stack).
您只有7个字节,但是您正在写入第8个,第9个...第12个字节,因此会重写其他程序数据(粉碎堆栈)。
#include <string.h>
char* concat(char s[], char t[]){
int i, j;
i = j = 0;
char* u = (char*)malloc(strlen(s) + strlen(t)+1);//new string with enough space for both and \0
while (s[i] != '\0') {
u[i]=s[i];
i++;
}
while ((u[i++]=t[j++]) != '\0');
return u;
}
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