pthread_join导致分段错误。为什么？

Question

该代码接收一个包含10个文件名的输入文件，将它们存储到一个2d数组中，并创建10 + 1个线程：一个请求者和10个转换器。这只是一个框架，所以我的线程只打印他们的ID，我没有访问任何全局变量或共享变量或需要互斥锁的东西。那么，我应该怎么做才能避免出现分段错误？

#include <stdio.h> 
#include <stdlib.h> 
#include <pthread.h> 
#include <semaphore.h> 
#include <string.h> 
#include <time.h> 
#include <sys/wait.h> 
#include <sys/types.h> 
#include <sys/time.h> 
#include <math.h> 
#include <unistd.h> 
#include <errno.h> 

#define READ_BUFFER_LEN 16 
//#define MAX_LENGTH 128 

enum { 
    MAX_LENGTH = 512 
}; 

typedef struct FileNameArray { 
    size_t nfiles; /* Number of file names allocated and in use */ 
    size_t maxfiles; /* Number of entries allocated in array */ 
    char **files; /* Array of file names */ 
} FileNameArray; 


//GLOBAL vars 
int num_images, *threads_ids /*threads ids*/; 
pthread_t *threads; 

void deallocate2D(FileNameArray *names) { 
    size_t i; 
    for (i = 0; i < names->nfiles; i++) 
     free(names->files[i]); 
    free(names->files); 
    names->nfiles = 0; 
    names->files = 0; 
    names->maxfiles = 0; 
} 

int readInputFile(FILE *fp, FileNameArray *names) { 
    num_images = names->nfiles; 
    int max_lines = names->maxfiles; 
    char **file_names = names->files; 
    char line[MAX_LENGTH]; 
    char **final_filenames, **array; 

    while (fgets(line, sizeof line, fp) != NULL) { 
     if (line[0] != '\n') { 
      /* Remove newline from end of file name */ 
      char *nl = strchr(line, '\n'); 
      if (nl != 0) 
       *nl = '\0'; 
      if (num_images >= max_lines) { 
       max_lines += 100; 
       array = realloc(file_names, max_lines * sizeof (char*)); 
       if (array == NULL) { 
        fprintf(stderr, "Error reallocating space for 2d array: %s\n", 
          strerror(errno)); 
        return -1; 
       } 
       names->maxfiles = max_lines; 
       names->files = array; 
       file_names = array; 
      } 
      if ((file_names[num_images] = malloc(strlen(line) + 1)) == NULL) { 
       fprintf(stderr, "Error allocating space for 2d array: %s\n", 
         strerror(errno)); 
       return -1; 
      } 
      names->nfiles++; 
      strcpy(file_names[num_images], line); 
      printf("name of file %d is: %s \n", num_images, file_names[num_images]); 
      num_images++; 
     } 
    } 

    printf("Num_lines: %d\n", num_images); 
    //realloc to number of lines in the file, to avoid wasting memory 
    if ((final_filenames = realloc(file_names, num_images * sizeof (char*))) == NULL) { 
     fprintf(stderr, "Error reallocating space for 2d array: %s\n", 
       strerror(errno)); 
     return -1; 
    } 
    names->maxfiles = num_images; 
    names->files = final_filenames; 
    return 0; 
} 

void* requester(void* arg) { 

    printf("This is the requester thread\n"); 
    //sleep(1); 
    pthread_exit(NULL); 
    return NULL; 
} 

void* converter(void *id) { 
    int my_id = *((int*) id); 

    printf("Thread's id is: %d\n", my_id); 
    pthread_exit(NULL); 
    return NULL; 
} 

int main(int argc, char *argv[]) { 
    FileNameArray names = {0, 0, 0}; 
    int i, rc; 
    pthread_attr_t attr; 


    //check parameters 
    if (argc < 4) { 
     fprintf(stderr, "Usage: %s input_filename.ppm charWidth charHeight\n", 
       argv[0]); 
     return -1; 
    } 

    printf("Opening input file [%s]\n", argv[1]); 
    FILE *fpin = fopen(argv[1], "r"); 
    if (fpin == NULL) { 
     fprintf(stderr, "Could not open input file %s (%s)\n", 
       argv[1], strerror(errno)); 
     return -1; 
    } 

    if ((names.files = malloc(10 * sizeof (char*))) == NULL) { 
     fprintf(stderr, "Error allocating initial space for 2d array: %s\n", 
       strerror(errno)); 
     return -1; 
    } 
    names.maxfiles = 10; 

    if (readInputFile(fpin, &names) == -1) { 
     fprintf(stderr, "Error reading image filenames from input\n"); 
     return -1; 
    } 

    threads = (pthread_t*) malloc(num_images + 1 * sizeof (pthread_t)); 
    threads_ids = (int*) malloc(num_images + 1 * sizeof (int)); 

    /* Initialize and set thread detached attribute */ 
    pthread_attr_init(&attr); 
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); 
    //creates requester thread, the 1st one on the list 
    pthread_create(&threads[0], &attr, requester, &threads_ids[0]); 
    threads_ids[0] = 0; 

    //creates so many converter threads as the number of images to convert 
    for (i = 1; i < num_images + 1; i++) { 
     threads_ids[i] = i; 
     rc = pthread_create(&threads[i], &attr, converter, &threads_ids[i]); 
     if (rc) { 
      printf("ERROR; return code from pthread_create() is %d\n", rc); 
      exit(-1); 
     } 
    } 


    /* Free attribute and wait for the other threads */ 
    pthread_attr_destroy(&attr); 

    for (i = 0; i < num_images + 1; i++) { 
     printf("Waiting for thread nr %d\n", i); 
     rc = pthread_join(threads[i], NULL); 
     if (rc) { 
      printf("ERROR; return code from pthread_join() is %d\n", rc); 
      exit(-1); 
     } 
    } 

    fclose(fpin); 
    free(threads); 
    free(threads_ids); 
    printf("###########\n"); 

    deallocate2D(&names); 

    printf("Done!\n"); 
    return 0; 
} 

这是可能的。OUPUTS之一：

Num_lines: 10 
This is the requester thread 
Thread's id is: 1 
Thread's id is: 2 
Thread's id is: 3 
Thread's id is: 5 
Thread's id is: 4 
Thread's id is: 6 
Thread's id is: 7 
Thread's id is: 8 
Thread's id is: 9 
Waiting for thread nr 0 
Thread's id is: 10 
Segmentation fault 

，这是广发行的结果：

Program received signal SIGSEGV, Segmentation fault. 
0x001bfea9 in *__GI___libc_free (mem=0x804c278) at malloc.c:3724 
3724 malloc.c: No such file or directory. 
    in malloc.c 
(gdb) where 
#0 0x001bfea9 in *__GI___libc_free (mem=0x804c278) at malloc.c:3724 
#1 0x00120802 in *__GI__dl_deallocate_tls (tcb=<value optimized out>, 
    dealloc_tcb=112) at dl-tls.c:487 
#2 0x00133748 in __free_stacks (limit=41943040) at allocatestack.c:274 
#3 0x00133849 in queue_stack (pd=0xb5fd9b70) at allocatestack.c:302 
#4 __deallocate_stack (pd=0xb5fd9b70) at allocatestack.c:740 
#5 0x00134b37 in pthread_join (threadid=3053296496, thread_return=0x0) 
    at pthread_join.c:110 
#6 0x0804955c in main (argc=4, argv=0xbffff4a4) at main.c:261 

Answer 1

threads = (pthread_t*) malloc(num_images + 1 * sizeof (pthread_t)); 
threads_ids = (int*) malloc(num_images + 1 * sizeof (int)); 

当然，你必须有打算写

threads = malloc((num_images + 1) * sizeof (pthread_t)); 
threads_ids = malloc((num_images + 1) * sizeof (int)); 

或

threads = calloc(num_images + 1, sizeof (pthread_t)); 
threads_ids = calloc(num_images + 1, sizeof (int)); 

呢？