c - 内部循环执行一次段错误(核心转储)

Question

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct 
{
    int m_id;
    char m_name[20];
    char m_dept[20];
    int m_salary;
}Employee ;

int main()
{
    FILE *fptr;
    char ch;
    int flag=0;
    int j=0;
    int static i ;
    Employee *e=malloc(1 * sizeof(Employee));
    fptr=fopen("srs.txt","r");
    if(fptr==NULL)
    {
        printf("\nError in opening file 1!!!\n");
        return 0;
    }
    printf("\nFile opened successfully\n");
    printf("\n\n file content :\n\n");
    while((fscanf(fptr,"%c",&ch))!=EOF)
    {

        {
              while((fscanf(fptr,"%d%s%s%d",&e[i].m_id,&e[i].m_name,&e[i].m_dept,&e[i].m_salary)==4))
              {
                e=(Employee *)realloc(e,sizeof(Employee)+i+1);
                i++;
                flag=1;
              } 
        }

    }

    for(j=0;j<=i;j++)
    {
        printf("\nEMPLOYEE ID IS     : %d",e[j].m_id);
        printf("\nEMPLOYEE NAME IS   : %s",e[j].m_name);
        printf("\nEMPLOYEE DEPT IS   : %s",e[j].m_dept);
        printf("\nEMPLOYEE SALARY IS : %d",e[j].m_salary);
    }

    if(flag==0)
    printf("\nRec not found 2 \n");
    fclose(fptr);
    return 0;
}




/* file contain following data , number of employee not fixed 
ID      NAME        DEPT        SALARY

1       SAM         CAE         111
2       DHAN        CAE         222
3       PRINCE      DEVP        333
*/

Answer 1

我稍微重组了您的代码，但尝试尽可能接近您的版本。我用 valgrind 仔细检查了下面的解决方案，它没有泄漏。

假设测试文件中的文件内容(如源代码中所述)具有如下示例所示的结构:

1       SAM         CAE         111
2       DHAN        CAE         222
3       PRINCE      DEVP        333

意味着没有前导空行或描述。它可以添加，但我想重点关注如何动态增长数据结构。

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

typedef struct 
{
    int m_id;
    char* m_name;
    char* m_dept;
    int m_salary;
} Employee;

/*
 * Contract
 * --------
 * This program tries to open a file named 'srs.txt' and assumes the following
 * structure in each line:
 * <integer> <string> <string> <integer>
 */
int main()
{
    FILE *fptr;

    // Think of 'e' as a pointer to an array of pointers to 'Employee' structs that
    // will grow on demand
    Employee **e= (Employee**) malloc(1 * sizeof(Employee**));
    fptr=fopen("srs.txt","r");
    if(fptr==NULL)
    {
        printf("\nError in opening file 1!!!\n");
        return 0;
    }
    printf("\nFile opened successfully\n");
    printf("\n\n file content :\n\n");


      int tmp_id;
      char* tmp_name = (char*)malloc(sizeof(char)*20);
      char* tmp_dept = (char*)malloc(sizeof(char)*20);
      int tmp_salary;

      int i = 0;
      while( (fscanf(fptr,"%d%s%s%d",&tmp_id,tmp_name, tmp_dept, &tmp_salary)) == 4 )
      {

            // Create a new employee on the heap
            Employee* employee =  (Employee*) malloc (1 * sizeof(Employee));
            employee->m_id = tmp_id;
            employee->m_name = tmp_name;
            employee->m_dept = tmp_dept;
            employee->m_salary = tmp_salary;

            // Reserve memory for next iteration
            // the outer scope of this while loop needs to free the memory
            // pointed to by 'tmp_name' and 'dept_name'!!!
            tmp_name = (char*)malloc(sizeof(char)*20);
            tmp_dept = (char*)malloc(sizeof(char)*20);

            i = i + 1;
            e=(Employee **)realloc( e,(sizeof(Employee**)*i) );
            e[i-1] = employee;
      }
      free(tmp_name);
      free(tmp_dept);

    int j= 0;
    for(j=0;j<i;j++)
    {
        printf("\nEMPLOYEE ID IS     : %d",e[j]->m_id);
        printf("\nEMPLOYEE NAME IS   : %s",e[j]->m_name);
        printf("\nEMPLOYEE DEPT IS   : %s",e[j]->m_dept);
        printf("\nEMPLOYEE SALARY IS : %d\n",e[j]->m_salary);

    }

    fclose(fptr);

    // Clean up the heap memory
    for(j=(i-1);j>=0;j--){
        free(e[j]->m_name);
        free(e[j]->m_dept);
        free(e[j]);
    }

    free(e);

    return 0;
}