“test.exe遇到了断点”

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

#define INITALLOC   16
#define STEP         8

int main(int argc,char *argv[])
{
    if (horzmerge(argc - 1,argv + 1) == 0) {
        perror("horzmerge");
        return EXIT_FAILURE;
    }
    getchar();
    return EXIT_SUCCESS;
}
int horzmerge(int nfiles,const char **filenames)
{
    FILE **files;
    char *line;
    int i;

    if ((files = malloc(nfiles * sizeof (FILE *))) == NULL)
        return 0;

    for (i = 0; i < nfiles; ++i)
        if ((files[i] = fopen(filenames[i],"r")) == NULL)
            return 0;

    do {
        for (i = 0; i < nfiles; ++i) {
            if (getline(files[i],&line) == 0)
                return 0;
            fprintf(stdout,"%s",line);
            free(line);
        }
        putchar('n');
    } while (!feof(files[0]));  /* we can still get another line */

    for (i = 0; i < nfiles; ++i)
        fclose(files[i]);
    free(files);
    return 1;
}
int getline(FILE *fp,char **dynline)
{
    size_t nalloced = INITALLOC;
    int c,i;

    if ((*dynline = calloc(INITALLOC,sizeof(char))) == NULL)
        return 0;

    for (i = 0; (c = getc(fp)) != EOF && c != 'n'; ++i) {
        if (i == nalloced)
            if ((*dynline = realloc(*dynline,nalloced += STEP)) == NULL)
                return 0;
        (*dynline)[i] = c;
    }
    (*dynline)[i] = '';
    if (c == EOF)
        return EOF;
    return i;
}

我放置了断点,并看到它是horzmerge中的自由(行)语句.但有时程序运行正常.有时却没有.有时我会在getline中收到“堆损坏”.我已经在这个代码上工作了一个星期,仍然找不到bug.