[英]How to fix seg fault when strcat two char pointers
I get a segmentation fault because of my code with pointers.由于我的代码带有指针,我遇到了分段错误。 (Pointers are there needed.)
(需要指针。)
int main()
{
char *dns_name = ".";
char *dns_name2 = ".";
printf("HELLO\n");
strcat(dns_name2,dns_name);
printf("result: %s", *dns_name2);
return 0;
}
The problem in your code is that the lines:您的代码中的问题是这些行:
char *dns_name = ".";
char *dns_name2 = ".";
each allocate a fixed length array of characters to dns_name
and dns_name2
, each being two characters long (one for the dot and one for the nul
terminator).每个都为
dns_name
和dns_name2
分配一个固定长度的字符数组,每个字符长度为两个字符(一个用于点,一个用于nul
终止符)。
To fix the problem, you need to declare the strings as longer arrays, capable of holding the maximum expected length of the result of the strcat
call:要解决此问题,您需要将字符串声明为更长的 arrays,能够保持
strcat
调用结果的最大预期长度:
char dns_name[50] = "."; // Change 50 to the maximum allowable length.
char dns_name[50] = ".";
Also, in your output line, you shouldn't dereference the string pointer, So: instead of:此外,在您的 output 行中,您不应取消引用字符串指针,因此: 而不是:
printf("result: %s", *dns_name2);
use:利用:
printf("result: %s", dns_name2); // the %s format expects a pointer or array.
Hope this helps.希望这可以帮助。 Feel free to ask for further clarification and/or explanation.
随时要求进一步澄清和/或解释。
EDIT: If you need dns_name
and dns_name2
to be actual pointers, then you can create the character arrays as separate variables and point yours to them:编辑:如果您需要
dns_name
和dns_name2
作为实际指针,那么您可以创建字符 arrays 作为单独的变量并将您的指向它们:
char dns_buffer[50] = ".";
char dns_buffer2[50] = ".";
char *dns_name = dns_buffer;
char *dns_name2 = dns_buffer2;
You may give that a try.你可以试试看。 It uses dns_buffer and dns_buffer2 to create a dynamically allocated string.
它使用 dns_buffer 和 dns_buffer2 创建动态分配的字符串。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char *dns_name = "hh";
char *dns_name2 = "hhha";
char *total_dns = malloc(strlen(dns_name) + strlen(dns_name2) + 1);
printf("HELLO\n");
strcpy(total_dns, dns_name);
strcat(total_dns,dns_name2);
printf("result: %s", total_dns);
free(total_dns);
return 0;
}
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