C 错误 - free() : invalid next size (fast)

Question

我不确定为什么会收到以下错误。奇怪的是，当我使用 Mac OS X 时不会出现此错误，但当我使用 Linux (Debian) 分区时会出现此错误。

-----------
Empty Queue: 0 0 0 0 0 0 0 0 0 0 

---------------
Populated Queue: 5 3 1 7 6 3 2 1 4 4 

-------------
After Dequeue: 3 1 7 6 3 2 1 4 4 0 
    Datum: 5

*** glibc detected *** ./queue_demo: free(): invalid next size (fast): 0x0000000000c73010 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x75b76)[0x7fde5c98db76]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x6c)[0x7fde5c9928ac]
./queue_demo[0x40098d]
./queue_demo[0x4008d8]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xfd)[0x7fde5c936ead]
./queue_demo[0x4006d9]
======= Memory map: ========
00400000-00401000 r-xp 00000000 08:01 940937                             /home/dylan/Desktop/CST352_Gleason_Lab2/solution_1/queue_demo
00601000-00602000 rw-p 00001000 08:01 940937                             /home/dylan/Desktop/CST352_Gleason_Lab2/solution_1/queue_demo
00c73000-00c94000 rw-p 00000000 00:00 0                                  [heap]
7fde58000000-7fde58021000 rw-p 00000000 00:00 0 
7fde58021000-7fde5c000000 ---p 00000000 00:00 0 
7fde5c702000-7fde5c717000 r-xp 00000000 08:01 1079347                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fde5c717000-7fde5c917000 ---p 00015000 08:01 1079347                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fde5c917000-7fde5c918000 rw-p 00015000 08:01 1079347                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fde5c918000-7fde5ca95000 r-xp 00000000 08:01 1079316                    /lib/x86_64-linux-gnu/libc-2.13.so
7fde5ca95000-7fde5cc95000 ---p 0017d000 08:01 1079316                    /lib/x86_64-linux-gnu/libc-2.13.so
7fde5cc95000-7fde5cc99000 r--p 0017d000 08:01 1079316                    /lib/x86_64-linux-gnu/libc-2.13.so
7fde5cc99000-7fde5cc9a000 rw-p 00181000 08:01 1079316                    /lib/x86_64-linux-gnu/libc-2.13.so
7fde5cc9a000-7fde5cc9f000 rw-p 00000000 00:00 0 
7fde5cc9f000-7fde5ccbf000 r-xp 00000000 08:01 1079447                    /lib/x86_64-linux-gnu/ld-2.13.so
7fde5cea3000-7fde5cea6000 rw-p 00000000 00:00 0 
7fde5cebb000-7fde5cebe000 rw-p 00000000 00:00 0 
7fde5cebe000-7fde5cebf000 r--p 0001f000 08:01 1079447                    /lib/x86_64-linux-gnu/ld-2.13.so
7fde5cebf000-7fde5cec0000 rw-p 00020000 08:01 1079447                    /lib/x86_64-linux-gnu/ld-2.13.so
7fde5cec0000-7fde5cec1000 rw-p 00000000 00:00 0 
7fff13797000-7fff137b8000 rw-p 00000000 00:00 0                          [stack]
7fff137ff000-7fff13800000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted

当我在下面编写的测试程序中调用队列结构中的 destruct 函数时，会发生此错误。

#include <time.h>
#include <stdio.h>
#include "Queue.h"

int main(int argc, char* argv[])
{
   // create a "queue" data structure
   Queue_t* my_queue = construct(10);

   // generate a random seed
   srand( (unsigned)time(NULL) );

   // display the empty queue
   printf("-----------\n");
   printf("Empty Queue: ");
   display(my_queue);
   printf("\n");

   // populate the queue with random numbers
   int i = 0;

   for(; i < my_queue->maximum_count; ++i)
      enqueue(my_queue, rand() % 10);

   printf("---------------\n");
   printf("Populated Queue: ");
   display(my_queue);
   printf("\n");

   // dequeue, print the current queue and the datum
   int datum = dequeue(my_queue);

   printf("-------------\n");
   printf("After Dequeue: ");
   display(my_queue);
   printf("\tDatum: %d\n\n", datum);

   // clean up memory
   destruct(my_queue);

   return 0;
}

这是我的数据结构:

#ifndef QUEUE_H
#define QUEUE_H

typedef struct Queue
{
   int  current_count;
   int  maximum_count;
   int  buffer[];       // queue uses an array
} Queue_t;


// routines to implement Queue-like functionality (FIFO)
// TODO: somehow encapsulate all these features in the struct itself.
//
Queue_t* construct(int buff_size);
void     destruct (Queue_t* queue);
void     display  (Queue_t* queue);
int      dequeue  (Queue_t* queue);
void     enqueue  (Queue_t* queue, const int datum);

#endif

实现:

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "Queue.h"

Queue_t* construct(int buff_size)
{
   Queue_t* queue = malloc(
      sizeof(Queue_t) + sizeof(int) * sizeof(Queue_t));

   assert(queue != NULL);
   queue->maximum_count = buff_size;
   queue->current_count = 0;
   memset(queue->buffer, 0, sizeof(int)*buff_size);

   return queue;
}

void destruct(Queue_t* queue)
{
   assert(queue != NULL);
   free(queue);  // error at this statement
   printf("Queue destroyed!\n");
}

void display(Queue_t* queue)
{
   int i = 0;

   for(; i < queue->maximum_count; ++i)
      printf("%d ", queue->buffer[i]);
   printf("\n");
}

void enqueue(Queue_t* queue, const int datum)
{
   assert(queue->current_count < queue->maximum_count);
   queue->buffer[queue->current_count] = datum;
   ++queue->current_count;
}


int dequeue(Queue_t* queue)
{
   int i = 1;
   int datum = queue->buffer[0];

   assert(queue->current_count > 0);

   for(; i < queue->maximum_count; ++i)
   {
      queue->buffer[i-1] = queue->buffer[i];
      queue->buffer[i] = 0;
   }

   --queue->current_count;

   return datum;
}

Answer 1

这看起来您损坏了 libc 内存分配函数使用的一些数据。在你的 construct 函数中，我们不应该改变

Queue_t* queue = malloc(
      sizeof(Queue_t) + sizeof(int) * sizeof(Queue_t));

到

Queue_t* queue = malloc(
          sizeof(Queue_t) + sizeof(int) * buff_size);

由于为队列分配的内存量不正确，construct 中的以下行现在似乎会导致损坏。

 memset(queue->buffer, 0, sizeof(int)*buff_size);

当您将 sizeof 运算符应用于具有灵活数组成员的结构时，只有灵活数组以外的字段构成总结构大小，即它的大小为 0。当您为此类分配内存时结构，您需要明确指定在结构末尾需要多少个额外字节。