这个错误说明了什么

Question

当我试图执行我的程序时，它得到这样的错误-

sendip: malloc.c:4631: _int_malloc: Assertion `(unsigned long)(size)
 >= (unsigned long)(nb)' failed

尝试通过valgrind捕获错误，得到这个-

   HEAP SUMMARY:
   ==3335==     in use at exit: 24 bytes in 2 blocks 
   ==3335==   total heap usage: 111 allocs, 109 frees, 7,929 bytes allocated
   ==3335== 
   ==3335== 4 bytes in 1 blocks are definitely lost in loss record 1 of 2
   ==3335==    at 0x40268A4: malloc (vg_replace_malloc.c:236)
   ==3335==    by 0x8049EEF: main (sendip.c:435)
   ==3335== 
   ==3335== 20 bytes in 1 blocks are definitely lost in loss record 2 of 2
   ==3335==    at 0x40268A4: malloc (vg_replace_malloc.c:236)
   ==3335==    by 0x4031F57: ???
   ==3335==    by 0x804A338: main (sendip.c:521)
   ==3335== 

行不。435

              datalen = stringargument(gnuoptarg, &datarg);
      /*This is the line*/ data=(char *)malloc(datalen);
                            memcpy(data, datarg, datalen);

如果需要，我可以添加其他代码块…但帮我摆脱这个??

Answer 1

您一定是覆盖了"data"而忘记释放旧内容…你检查过这个了吗?

Answer 2

glibc的malloc()将元数据(例如块的长度，指向前一个块的指针，…)添加到返回给调用者的块中，因此在覆盖"数据"时，很容易损坏元数据。