realloc 错误读取文件

Question

我对这段代码有疑问。有时它运行完美，但有时它在最后一次打印之前停止并显示错误消息："Error in './ga': realloc(): invalid pointer: 0x00007f97d1304ac6".

我疯了，因为我没有使用 realloc()！

我怀疑文件reding部分有问题，因为我把这部分添加到代码中时出现了这个问题（之前我用其他两个数组设置数据）

#include <limits> // std::numeric_limits<double>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>
#include <utility>
//#include <math.h>
#include <algorithm>    // std::lower_bound, std::find
#include <random>
#include <cmath> 
#include <cstring>
#include <iomanip>      // std::setprecision
#include <vector>       // std::vector

#define NUM_CITIES 14 

long size_pop;
long tot_elem;


int main(int argc, char *argv[]) {

    size_pop = atol(argv[1]);

    std::cout << size_pop << "\n";

    std::cout << "double: " << sizeof(double) << "\n";
    std::cout << "float: " << sizeof(float) << "\n";
    std::cout << "int: " << sizeof(int) << "\n";
    std::cout << "long: " << sizeof(long) << "\n";

    tot_elem = NUM_CITIES * size_pop;
    std::cout << "tot_elem: " << tot_elem << "\n";

    // std::cin.get() != '\n';

    struct timeval start, end, setup_start, setup_end, fitness_start, fitness_end, next_gen_start, next_gen_end, sort_start, sort_end;
    struct timeval fitness_total_start, fitness_total_end, probability_start, probability_end, selection_start, selection_end;
    struct timeval crossover_start, crossover_end, mutation_start, mutation_end;
    gettimeofday(&start, NULL);

    std::vector<double> v_set;
    std::vector<double> v_fit;
    std::vector<double> v_sor;
    std::vector<double> v_sel;
    std::vector<double> v_cros;
    std::vector<double> v_mut;

    // coordinate delle città
    // int x[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    // int y[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // città
    //city city_set[NUM_CITIES];
    int city_set_x[NUM_CITIES];
    int city_set_y[NUM_CITIES];
    int city_set_id[NUM_CITIES];

    // popolazione composta da path (possibii soluzioni al problema)
    int *city_x = (int *)malloc(tot_elem * sizeof(int));
    // memset(city_x, -1, tot_elem * sizeof(int));
    int *city_y = (int *)malloc(tot_elem * sizeof(int));
    // memset(city_y, -1, tot_elem * sizeof(int));
    int *city_id = (int *)malloc(tot_elem * sizeof(int));
    // memset(city_id, -1, tot_elem * sizeof(int));
    fit *fitness_element = (fit *)malloc(size_pop * sizeof(fit));

    // mating_pool, i migliori elementi della popolazione
    int *mating_x = (int *)malloc(NUM_CITIES * SIZE_MATING * sizeof(int));
    int *mating_y = (int *)malloc(NUM_CITIES * SIZE_MATING * sizeof(int));
    int *mating_id = (int *)malloc(NUM_CITIES * SIZE_MATING * sizeof(int));

    srand(time(NULL));

    // std::cin.get() != '\n';
    std::cout << "read from file\n";

    // leggo le coordinate delle città
    const char *filename = "/home/davide/Documenti/GA/BURMA14.txt";

    char *line;
    size_t n = 5;

    FILE *coordFile = fopen(filename, "r");
    //FILE *f = fopen("/home/davide/Documenti/GA/result.txt", "w");

    int i; // indice dell'array
    int x, y; // coordinate delle città

    while(getline(&line, &n, coordFile) != -1 && i <= NUM_CITIES)
    {
        int items = sscanf(line, "%d %d %d", &i, &x, &y);
        if(items != 3)
            exit(EXIT_FAILURE);
        --i;
        //std::cout << x << "\n";
        //std::cout << y << "\n";
        //std::cout << i << "\n";

        city_set_x[i] = x;
        city_set_y[i] = y;
        city_set_id[i] = i;
    }
    fclose(coordFile);

    // std::cin.get() != '\n';


    // stampa
    std::cout << "[CITTA.X]\n";
    for(int i = 0; i < NUM_CITIES; ++i) {

        // city_set_x[i] = x[i];
        // city_set[i].x = i + 1;
        std::cout << city_set_x[i] << " ";
    }
    std::cout << "\n";

    std::cout << "[CITTA.Y]\n";
    for(int i = 0; i < NUM_CITIES; ++i) {

        // city_set_y[i] = y[i];
        // city_set[i].y = i + 1;
        std::cout << city_set_y[i] << " ";
    }
    std::cout << "\n";

    std::cout << "[CITTA.ID]\n";
    for(int i = 0; i < NUM_CITIES; ++i) {

        // city_set_id[i] = i;
        std::cout << city_set_id[i] << " ";
    }
    std::cout << "\n";
}

我看的文件是这个

Answer 1

此代码错误：

char *line;
size_t n = 5;
...
int i; // indice dell'array
...
while(getline(&line, &n, coordFile) != -1 && i <= NUM_CITIES)
{
    int items = sscanf(line, "%d %d %d", &i, &x, &y);
...

line 未初始化，这几乎肯定会导致报告的 realloc() 错误。

根据 the getline() standard:

The application shall ensure that *lineptr is a valid argument that could be passed to the free() function. If *n is non-zero, the application shall ensure that *lineptr either points to an object of size at least *n bytes, or is a null pointer.

注意 i 也没有被初始化，它的值直到 while() 循环开始后立即调用 sscanf() 才被设置。但是 i 用于 while-loop 的条件子句，可能会导致循环控制出现问题。

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