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Re: Where is free() implemented?
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Preston Moore <prestonkmoore at gmail dot com>, libc-help at sourceware dot org
- Date: Tue, 24 May 2016 15:09:37 -0400
- Subject: Re: Where is free() implemented?
- Authentication-results: sourceware.org; auth=none
- References: <80965656-C371-4702-A98E-2AFBAF318832 at gmail dot com>
On 05/24/2016 02:47 PM, Preston Moore wrote:
> Hey everyone,
>
> Hopefully this is a quick question with a quick answer. Where is
> free() implemented? Iâve just found a bunch of extern references in
> the glibc source I have. This is Ubuntu 14.04 LTS 32 bit.
In most GNU/Linux applications the function free() is implemented in
the shared library libc.so.6 (part of glibc) and is part of the memory
allocation API provided by the core runtime. The functionality of free
is defined in the ISO C standard.
However, the memory allocation API is designed to be "replaceable"
via what is called "ELF symbol interposition" which means you can load
another shared library via LD_PRELOAD and have that shared library
provide a replacement implementation of the API. This is the case when
you're using other memory allocation libraries like jemalloc, tcmalloc,
or hoard.
--
Cheers,
Carlos.