Linking un-referenced function

[Meissner, Michael]

The linker option --gc-sections (ie, from the GCC command line:
	-ffunction-sections -fdata-sections -Wl,--gc-sections

Will do the collection.  You need the two -f options so that the
compiler puts each function/data item into a separate section, and then
the --gc-sections option will enable the linker to remove any section
that is not referenced.

--
Michael Meissner
AMD, MS 83-29
90 Central Street
Boxborough, MA 01719

-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
Behalf Of Jason Lam
Sent: Tuesday, May 23, 2006 3:35 PM
To: John Carter
Cc: gcc-help@gcc.gnu.org
Subject: Re: Linking un-referenced function

Thanks for the quick response, John.

It looks like these options will arrange the functions
to different sections in the final image but it still
doesn't exclude them.  Am I missing something?

Thanks,

Jason

--- John Carter <john.carter@tait.co.nz> wrote:

> On Mon, 22 May 2006, Jason Lam wrote:
> 
> > I looked through the documents and couldn't find
> an
> > option to not link an un-referenced function into
> the
> > final image.  Does GCC support it?  Could someone
> > please help?
> 
> Sorry, I got confuddled...
> 
> Use
>    `--gc-sections'
> option on linker and...
> 
> 
> `-ffunction-sections'
> `-fdata-sections'
>       Place each function or data item into its own
> section in the output
>       file if the target supports arbitrary
> sections.  The name of the
>       function or the name of the data item
> determines the section's name
>       in the output file.
> 
>       Use these options on systems where the linker
> can perform
>       optimizations to improve locality of reference
> in the instruction
>       space.  Most systems using the ELF object
> format and SPARC
>       processors running Solaris 2 have linkers with
> such optimizations.
>       AIX may have these optimizations in the
> future.
> 
>       Only use these options when there are
> significant benefits from
>       doing so.  When you specify these options, the
> assembler and
>       linker will create larger object and
> executable files and will
>       also be slower.  You will not be able to use
> `gprof' on all
>       systems if you specify this option and you may
> have problems with
>       debugging if you specify both this option and
> `-g'.
> 
> 
> John Carter                             Phone :
> (64)(3) 358 6639
> Tait Electronics                        Fax   :
> (64)(3) 359 4632
> PO Box 1645 Christchurch                Email :
> john.carter@tait.co.nz
> New Zealand
> 
> Carter's Clarification of Murphy's Law.
> 
> "Things only ever go right so that they may go more
> spectacularly wrong later."
> 
> From this principle, all of life and physics may be
> deduced.
> 


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