Question

我的整个程序根据用户输入的文件名和模式创建一个新文件，然后检查该文件是否存在。然后输出文件创建是否成功。它应该很简单，但是当我使用Geany编译和构建（成功）并运行时，我在终端窗口中收到以下错误（但只有在进入模式＆＃34; r +＆＃34;后）：

./geany_run_script.sh: line 5:  7395 Segmentation fault      (core dumped) "./test" c


------------------
(program exited with code: 139)
Press return to continue

然后我在阅读了这个

之后用gdb运行它

segmentation fault (core dump)

并收到此错误：

Program received signal SIGSEGV, Segmentation fault.
_IO_new_fclose (fp=0x0) at iofclose.c:54
54  iofclose.c: No such file or directory.

这是我的代码：

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

char filename[100];
char mode[2];

int main(int argc, char **argv)
{
    printf("Enter filename:\n>");
    scanf("%s", &*filename);
    printf("Select a mode from the list:\nr reading\nw writing\na append\nr+ reading &   writing (at beginning, overwriting)\nw+ reading & writing (overwrite on existing)\na+ reading & appending (new data appended at end of file)\n>");
    scanf("%s", &*mode);

    FILE * fp;
    fp = fopen(filename, mode);

    if (fp == NULL)
    {
        printf("Failed to open\n");
    }
    else
    {
        printf("Succesfully opened\n");
    }
    fclose(fp);

    return 0;
}

输入文件名后出现gdb错误，与Geany不同，我输入模式后出现错误＆＃34; r +＆＃34;。

请提供帮助，只需询问您是否需要其他数据。提前谢谢。

编辑：我更新了代码，以及有关何时收到错误的信息。出于某种原因，它现在在程序中的不同点取决于我是使用gdb还是使用Geany运行它。

Answer 1

文件模式需要超过2个字符：＆＃34; r +＆＃34;等（NUL终结者）。小心避免缓冲区溢出。

   char mode[3];
   fgets(mode, sizeof(mode), stdin);

fclose在非打开文件上的行为未定义。

if (fp == NULL) {
    printf("Failed to open\n");
} else {
    printf("Succesfully opened\n");
    fclose(fp); /* only close if fp != NULL, and only close once */
}

所有在一起：

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


int main(int argc, char **argv) {
    char filename[100];
    char mode[3];
    char *p;

    printf("Enter filename:\n>");
    fgets(filename, sizeof(filename), stdin);
    if ((p = strchr(filename, '\n')) != NULL) {
      *p = '\0'; /* remove any newline */
    }

    printf("Select a mode from the list:\n"
        "r reading\n"
        "w writing\n"
        "a append\n"
        "r+ reading & writing (at beginning, overwriting)\n"
        "w+ reading & writing (overwrite on existing)\n"
        "a+ reading & appending (new data appended at end of file)\n>");

    fgets(mode, sizeof(mode), stdin);
    if ((p = strchr(mode, '\n')) != NULL) {
      *p = '\0';
    }

    printf("opening %s with mode %s.\n", filename, mode);
    FILE *fp = fopen(filename, mode);

    if (fp == NULL) {
        printf("Failed to open\n");
    } else {
        printf("Succesfully opened\n");
        fclose(fp);
    }
    return 0;
}

Geany错误代码139：使用C进行分段错误（核心转储）

1 个答案: