Question

嗨，我非常喜欢编码，我最近打了一个砖墙

这个程序有一个分段错误调试，我认为它与为缓冲区数组或输入文件分配空间有关，因为那些在搜索答案时一直作为解决方案弹出。如果你知道我做错了什么，如果你告诉我而不是给我解决方案，我将不胜感激。我完全失去了如何为任何东西分配内存，所以如果有人解释如何在代码的上下文中分配内存，那将会很棒。

应该读取这样结构的文件

2
3 4
3 4

其中2 =正在下载的文件数量，3 =文件的Kb / s（每行代表一个文件），4 =完成前剩余的时间。该程序应该输出一个文件，该文件具有下载所有内容所需的时间（当文件完成速度升级到其他人时请注意）

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

int main(void) {
  FILE *in = fopen("download.in", "r");
  FILE *out = fopen("download.out", "w");
  int i, n, j, a, k, o;
  char buffer[100];

  fgets(buffer, 10, in);
  sscanf(buffer, "%d", &n);
  int tn[n];
  int xn[n];

  i = 0;
  while (i < n) {
    fgets(buffer, 100, in);
    sscanf(buffer, "%d %d", &tn[i], &xn[i]);
    ++i;
  }
  for (i = 0; i < n; ++i){
    for (j = i + 1; j < n; ++j){
      if (tn[i] > tn[j]){
        a =  tn[i];
        tn[i] = tn[j];
        tn[j] = a;

        a =  xn[i];
        xn[i] = xn[j];
        xn[j] = a;
      }
    }

  }
  i = 1;
  float b ;
  k = 0;
  o = 1;
  while(o < n){
    if(xn[o] == xn[o - 1]){
      k = tn[o] + tn[o - 1]
      ;
    }
    else{
      b = (tn[o] * xn[o]) / (tn[o] + tn[o - 1] + k);
      k = 0;
    }
    ++o;
  }


  fprintf( out, "%f", b  );

  fclose(in); fclose(out);


  return 0;
}

我知道它给出的答案并不准确但我想先解决分段错误然后处理

gdb r然后gdb bt返回此

(gdb) r 
Program received signal SIGSEGV, Segmentation fault.                                                                   
_IO_fgets (buf=0x7fffffffeb30 "", n=10, fp=0x7fffffffeac0) at iofgets.c:50                                             
50      iofgets.c: No such file or directory.                                                                          
(gdb) bt                                                                                                               
#0  _IO_fgets (buf=0x7fffffffeb30 "", n=10, fp=0x7fffffffeac0) at iofgets.c:50                                         
#1  0x0000000000400766 in main () at main.c:11

codeblocks说代码没问题，而我试图给出的网站也说有分段错误。

Answer 1

以下是修复了segfault的代码。我必须（1）指定绝对路径和（2）将循环更改为for循环。

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

int main(void) {
    FILE *in = fopen("/home/developer/CLionProjects/untitled4/download.in", "r");
    FILE *out = fopen("/home/developer/CLionProjects/untitled4/download.out", "w");
    int i, n, j, a, k, o;
    char buffer[100];

    fgets(buffer, 10, in);
    sscanf(buffer, "%d", &n);
    int tn[n];
    int xn[n];

    for (i = 0; i < n; i++) {
        if (!fgets(buffer, 100, in)) break;
        if (sscanf(buffer, "%d %d", &tn[i], &xn[i]) < 2) break;
    }


    for (i = 0; i < n; ++i) {
        for (j = i + 1; j < n; ++j) {
            if (tn[i] > tn[j]) {
                a = tn[i];
                tn[i] = tn[j];
                tn[j] = a;

                a = xn[i];
                xn[i] = xn[j];
                xn[j] = a;
            }
        }

    }
    i = 1;
    float b;
    k = 0;
    o = 1;
    while (o < n) {
        if (xn[o] == xn[o - 1]) {
            k = tn[o] + tn[o - 1];
            fprintf(out, "Some number: %d\n", k);
        } else {
            b = (tn[o] * xn[o]) / (tn[o] + tn[o - 1] + k);
            k = 0;
            fprintf(out, "Some number: %d\n", k);
        }
        ++o;
    }

    fclose(in);

    const char *text = "Write this to the file";
    fprintf(out, "Some text: %s\n", text);

    fclose(out);

    int c;

    FILE *file;
    file = fopen("/home/developer/CLionProjects/untitled4/download.out", "r");
    if (file) {
        while ((c = getc(file)) != EOF)
            putchar(c);
        fclose(file);
    }

    return 0;
}

分配问题导致的细分错误？

1 个答案: