idea for ld feature: eliding unreferenced input sections

idea for ld feature: eliding unreferenced input sections

[Roland McGrath]

How hard do people think it would be to add an ld feature as follows?

I have in mind a new option, perhaps `--remove-unneeded-sections', that
would tell ld to discard from the output any input sections to which no
relocs in other sections refer.  It could be positional and apply to some
input files and not others, or it could just take the input section
containing the entry point as the root of the section dependency graph. 

I am thinking of using this in combination with something like gcc's
`-ffunction-sections' to achieve the effect of splitting up object files
and omitting the unreferenced ones from the link.

You can think of it as a moral equivalent to `--no-whole-archive' (the
default state of the switch being inverted, of course), considering each
object file to be an "archive of sections".  (The important difference is
that you still have a local symbol scope in each "archive" object file.)


Comments?


Thanks,
Roland

Re: idea for ld feature: eliding unreferenced input sections

[Ian Lance Taylor]

   Date: Wed, 7 Jul 1999 18:52:40 -0400
   From: Roland McGrath <roland@frob.com>

   How hard do people think it would be to add an ld feature as follows?

   I have in mind a new option, perhaps `--remove-unneeded-sections', that
   would tell ld to discard from the output any input sections to which no
   relocs in other sections refer.  It could be positional and apply to some
   input files and not others, or it could just take the input section
   containing the entry point as the root of the section dependency graph. 

It's a great idea, and Richard Henderson has already implemented it
for most ELF targets.  It's called --gc-sections.

Ian

Re: idea for ld feature: eliding unreferenced input sections

[Roland McGrath]

> It's a great idea, and Richard Henderson has already implemented it
> for most ELF targets.  It's called --gc-sections.

Well, there you go.  That'll show me to read the documentation in a
released version instead of the current development sources!

Thanks,
Roland

Re: idea for ld feature: eliding unreferenced input sections

[Mark E.]

> It's a great idea, and Richard Henderson has already implemented it
> for most ELF targets.  It's called --gc-sections.

Just out of curiousity, how hard would it be to implement for COFF 
targets?

Mark

--- 
Mark Elbrecht, snowball3@bigfoot.com
http://snowball.frogspace.net/

Re: idea for ld feature: eliding unreferenced input sections

[Richard Henderson]

On Wed, Jul 07, 1999 at 11:35:29PM -0400, Mark E. wrote:
> Just out of curiousity, how hard would it be to implement for COFF 
> targets?

Not too bad.


r~