从文件

如何解决从文件

我从一个文件中读取数据，我想放入一个结构中。这个结构包含一个可变大小的数组。所以我使用 realloc 来动态填充它。不幸的是我的程序失败了。 Valgrind 报告了一个带有 realloc 的 pb：

==3170== Invalid write of size 8
==3170==    at 0x1093E6: charge_Un_BV (charge_un_bv.c:56)
==3170==    by 0x109193: main (charge_un_bv.c:87)
==3170==  Address 0x4e507a8 is 8 bytes before a block of size 8 alloc'd
==3170==    at 0x4A3F2CC: realloc (in /home/linuxbrew/.linuxbrew/Cellar/valgrind/3.17.0/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==3170==    by 0x1093CD: charge_Un_BV (charge_un_bv.c:53)
==3170==    by 0x109193: main (charge_un_bv.c:87)

这是我的程序：

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

typedef struct st_BV {
    char nom_BV[40];
    int  id_bv;
    long  tabIndicePointsLength;
    long*  tabIndicePoints;
} BV;

BV* charge_Un_BV(char*); 
 
BV* charge_Un_BV(char* nomFileBV)
{
    BV* oneBV;
    oneBV = (BV*)malloc(sizeof(BV));
    if (oneBV == NULL) { printf("Erreur allocation mémoire\n"); exit(-6); }

    FILE* pt_fichier_BV = fopen(nomFileBV,"r");
    char ligne[100];
    long indice;
    float lon,lat;
    long count_ligne = 0;

    printf("start\n");  

    if (pt_fichier_BV == NULL)
    {
        printf("unable to open %s\n",nomFileBV);
        exit(-1);
    }
    else
    {
        printf("File opened\n");
        char* resultat = fgets(ligne,100,pt_fichier_BV);
        if (resultat == NULL) {printf("Error reading file\n"); exit(-2);}
        printf("First ligne skip: %s",ligne);
        
        
        oneBV->tabIndicePoints = (long*)malloc(sizeof(long));
        if (oneBV->tabIndicePoints == NULL) { printf("Error with alloc\n"); exit(-3); }

        int cr;
        
        do{
            cr = fscanf (pt_fichier_BV,"%ld %f %f",&indice,&lon,&lat);

            // reallocation according to the number of points read in the file
// BELOW LINE 53 :
            oneBV->tabIndicePoints = (long*)realloc(oneBV->tabIndicePoints,(count_ligne+1) * sizeof(long));
            if (oneBV->tabIndicePoints == NULL) { printf("Error realloc\n"); exit(-4); }
            
// BELOW LINE 56 :
            oneBV->tabIndicePoints[count_ligne-1] = indice;
            count_ligne++;
        }while(cr!=EOF);
        //total number of points
         oneBV->tabIndicePointsLength = count_ligne-1;
  //TEST
        printf("First indice (index): %ld\n",oneBV->tabIndicePoints[0]);
        printf("Fourth  indice (index): %ld\n",oneBV->tabIndicePoints[3]);
        printf("Total points: %ld\n",oneBV->tabIndicePointsLength);

    }
    //close file
    int cr = fclose(pt_fichier_BV);
    if (cr != 0)
    {
        printf("Erro closing file\n");
        exit(-5);
    }   
    return oneBV;
}


// Programme TEST
int main()
{
    BV* lebv;
// BELOW LINE 87 :
    lebv = charge_Un_BV("../data/data.txt");
    
    free (lebv);

    return 0;
}

所以我想知道用结构填充动态数组的正确方法是什么。 问候

在第一个解决方案后编辑

我将此问题添加到我的第一篇文章中。 valgrind 报告仍然给我关于内存泄漏的错误。我想，这来自于 realloc 之前的第一个 alloc 或来自最后一个 realloc。所以我有一块内存没有被释放。这不会阻止程序运行，但我们可以改进它吗？我添加了“免费（lebv）；”

==2858== 
début
Fichier ouvert
Première ligne: ind0 lon lat
Premier indice: 584119
Quatrième  indice: 584120
Nombre de points: 871
Quatrième  indice (2): 584120
==2858== 
==2858== HEAP SUMMARY:
==2858==     in use at exit: 6,976 bytes in 1 blocks
==2858==   total heap usage: 877 allocs,876 frees,3,050,688 bytes allocated
==2858== 
==2858== 6,976 bytes in 1 blocks are definitely lost in loss record 1 of 1
==2858==    at 0x4A3F2CC: realloc (in /home/linuxbrew/.linuxbrew/Cellar/valgrind/3.17.0/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==2858==    by 0x1093ED: charge_Un_BV (charge_un_bv.c:53)
==2858==    by 0x1091B0: main (charge_un_bv.c:87)
==2858== 
==2858== LEAK SUMMARY:
==2858==    definitely lost: 6,976 bytes in 1 blocks
==2858==    indirectly lost: 0 bytes in 0 blocks
==2858==      possibly lost: 0 bytes in 0 blocks
==2858==    still reachable: 0 bytes in 0 blocks
==2858==         suppressed: 0 bytes in 0 blocks
==2858== 
==2858== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

解决方法

您将 count_ligne 初始化为 0

    long count_ligne = 0;

然后从它之前减去1并将其用作索引（访问索引-1）

            oneBV->tabIndicePoints[count_ligne-1] = indice;
            count_ligne++;

您可能想要：

• 不减1，或
• 使用前递增