strcmp 的段错误

发布于 2024-11-14 22:48:54 字数 930 浏览 5 评论 0原文

我按以下方式使用 strcmp

传递 char[] 数组名称

传递指向字符串文字的指针但是，第二个结果导致段错误。尽管我已经确认指针指向正确的字符串文字，但我很困惑为什么会出现段错误。这是代码：-

#include ;
#include ;
#include ;

int main(int argc, char const *args[])
{
  char 第一个名称[strlen(*++args)];
  strcpy(名字, *args);
  char 姓氏[strlen(*++args)];
  strcpy(姓氏, *args);
  printf("%s\t%s\n", 名字, 姓氏);

  printf("%d\n", strcmp(firstName, lastName));// 这有效

  printf("%d\n", strcmp(*(--args),*(++args)));//这给了我一个段错误

  返回退出_成功；
}

我将其保存为 str.c ，当我编译它时，首先我收到以下警告：

[Neutron@Discovery examples]$ gcc -Wall str.c -o str

str.c: In function ‘main’:
str.c:15: warning: operation on ‘args’ may be undefined

最后运行它，给出一个 seg 错误，如下所示

[Neutron@Discovery examples]$ ./str Jimmy Neutron


Jimmy   Neutron

-4

Segmentation fault (core dumped)

原文

I am using strcmp in following ways

Passing char[] array names

Passing pointers to string literals
but, the second result in seg fault. even though i have confirmed that pointers point to correct string literals, i am confused as to why i am getting seg fault..
Here is the code:-

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

int main(int argc, char const *args[])
{
  char firstName[strlen(*++args)];
  strcpy(firstName, *args);
  char lastName[strlen(*++args)];
  strcpy(lastName, *args);
  printf("%s\t%s\n", firstName, lastName);

  printf("%d\n", strcmp(firstName, lastName));// this works

  printf("%d\n", strcmp(*(--args),*(++args)));//this gives me a seg fault

  return EXIT_SUCCESS;
}

I am saving it as str.c and when i compile it, first i get following warning:

[Neutron@Discovery examples]$ gcc -Wall str.c -o str

str.c: In function ‘main’:
str.c:15: warning: operation on ‘args’ may be undefined

finally running it, gives a seg fault as shown below

[Neutron@Discovery examples]$ ./str Jimmy Neutron


Jimmy   Neutron

-4

Segmentation fault (core dumped)

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云淡月浅 2024-11-21 22:48:54

当您将同一个变量作为两个不同的参数两次传递给同一个函数时，请勿使用 -- 和 ++。

而不是 printf("%d\n", strcmp(*(--args),*(++args)));

仍然

char *first = *(--args);
char *second = *(++args);
printf("%d\n", strcmp(first,second));

不真正可读（最好使用索引并检查 argc 的有效性），但至少您不会更改该值并在同一序列点对其进行多次评估。

Don't use -- and ++ when you pass the same variable to the same function twice as two different parameters.

Instead of printf("%d\n", strcmp(*(--args),*(++args)));

char *first = *(--args);
char *second = *(++args);
printf("%d\n", strcmp(first,second));

Still not really readable (better use indexes and check against argc for validity), but at least you don't change the value and evaluate multiple times it at the same sequence point.

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