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Re: why there is no memlen();
- From: John Love-Jensen <eljay at adobe dot com>
- To: Arunachalam G <arunachalam at deeproot dot co dot in>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Thu, 31 Oct 2002 06:58:39 -0600
- Subject: Re: why there is no memlen();
Hi Arun,
> What is that? going 4 bytes back & reading it give the amount of memory
> allocated.
It's how the heap manager keeps track of the lengths of the allocated
blocks. Note: not ALL heap managers use this particular bookkeeping trick.
> does it contains the attributes of the data type.
Hmmm, I suspect the answer is "no".
> and why it is compiler specific?
There are other ways to manage heaps. If you were writing your own heap
manager, you could (for instance) put the bookkeeping information in an
entirely separate block of memory.
Or perhaps you have a debugging heap manager that NEVER returns memory to
the pool, so it doesn't need to keep track of lengths. [Not recommended for
production code!]
> I use gcc 2.95.4 on linux in IA32. The above code gave some more addtional
> length than the actually allocated. (for 100 bytes it gave 105 & for 1000
> it gave 1009). Is it due to alignment?
Uncertain, but that sounds plausible.
--Eljay
GCC 3.2 on Cygwin
GCC 3.1 on OS X
GCC 2.95.2 on Solaris