Daniel Ellard wrote:

And let there be light...  DANG..  well it almost blinded me.  I was
confusing with char[16], which has the +1 byte for the null
terminating, but the malloc(16) hasn't...


No, that's still not quite it...

char[16] allocates exactly 16 characters.  Period.  There's no extra
space on the end for the terminating nul.  If you try to put a sixteen
character string into this array, the terminating nul will slop over
onto whatever follows this array in memory.

malloc(16) is essentially the same.  The difference is that there
might not be something right there to be clobbered.  malloc tends to
round up the number of bytes to something convenient.  It's easier to
manage a pool of things that are all the same size than a zillion
different sizes.  16 is pretty small -- the linux malloc might round
everything smaller than 20 bytes or 24 bytes (why 20 or 24?  That's
another story...) to 20 or 24 bytes bytes just to make its life
easier.  Therefore it's giving you four "extra" bytes and the nul can
clobber them without causing you to notice the bug.

-Dan


Yes. Thanks ;).



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