Dynamic memory allocation issue

[Joel Sherrill]

Robert S. Grimes wrote:
> I've run across this before, and I've used workarounds, later to find 
> the problem went away.  I thought it was something I was doing wrong 
> that I somehow stopped doing, as it didn't happen again for some 
> weeks/months - until this morning.  I added code like this:
>
>   uint8_t* faultTable_;
>
>   printk("Getting new fault table of size %d\n", sizeInBytes_);
>   faultTable_ = new uint8_t(sizeInBytes_);
>   printk("Got new fault table (%p)\n", faultTable_);
>   if (faultTable_) {
>     printk("Initializing new fault table (%p), size %u\n",
>            faultTable_, sizeInBytes_);
>     memset(faultTable_, 0, sizeInBytes_);   // <<== This is the problem?
>     printk("New fault table (%p) ready for use\n", faultTable_);
>   } else {
>     numFaults_ = sizeInBytes_ = 0;
>   }
>
> Here is what I get:
>
>   Getting new fault table of size 36
>   Got new fault table (6C2D90)
>   Initializing new fault table (6C2D90), size 36
>   New fault table (6C2D90) ready for use
>   PASS: 0 !front and back sizes don't match
>
> The last line of the output is from the heap walker.
>
>   
Can you break after the print of the address and see what
what is in memory from say address-16 to (address+size+16).
That should let us figure out if the block is underallocated
for some reason. 

Is there any sign of a failure other than heap walk?  It is
always positive it is a false positive but I wouldn't want to
let it go at that.
> If I delete the call to memset(), the problem goes away.  This is (more 
> surprisingly) even true if I defer the exact same call to memset() (i.e. 
> with the same pointer and size arguments) until (much) later!
>
> Oh, and it's not memset() per se, as a loop to clear the buffer at the 
> same location fails the same way.
>
> Any ideas?
>
> Thanks in advance!
> -Bob
>
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>   


-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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