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From: Ian Collins <ian-news@hotmail.com>
Newsgroups: comp.lang.c
Subject: Re: Open letter to Ian Collins
Date: Sun, 27 May 2012 15:16:15 +1200
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On 05/27/12 10:22 AM, jacob navia wrote:
> Hi Ian
>
> In the c++ newsgroup you asked me for an example of the ccl performance
> It was something with building a huge list, then sorting it, if I
> remember correctly...
>
> I have built this example code:
>
<snip>

I get a segv when I run the example.  Running in dbx with access 
checking enabled shows:

Write to unallocated (wua):
Attempting to write 1 byte at address 0x8091d88
     which is just past heap block of size 800 bytes at 0x8091a68
This block was allocated from:
         newHeapObject<-NewLink<-Add_nd<-Add<-main
Location of error: heap.c, line 75, newHeapObject()

The offending code appears to be here in heap.c:

      /* The array of block pointers is full. Allocate CHUNK_SIZE blocks 
more */
       siz = (l->BlockCount+CHUNK_SIZE)*sizeof(ListElement *);
       result = l->Allocator->realloc(l->Heap,siz);
       if (result == NULL) {
         return NULL;
       }
       l->MemoryUsed+= siz;
       l->Heap = (char **)result;
       /* Position pointer at the start of the new area */
       result += l->BlockCount*sizeof(ListElement *);
       /* Zero the new pointers */
       memset(result,0,siz);

It looks like you are allocating siz byes, incrementing part (half) way 
through the bock then zeroing the next siz bytes.

-- 
Ian Collins