what does this error suggest?

Question

When I am trying to execute my program Its getting error like this -

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

Tried capturing error through valgrind,got this one -

   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== 

Line no. 435

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

If needed I could add other pieces of code ... but help me getting out of this ??? What is this I am getting no clue ..

Solution

You must be overwriting "data" and forgetting to free the old content... have you checked this?