Re: Comments requested for proposed for ld scripting language extension

[Tristan Gingold <gingold at adacore dot com>]

On Apr 28, 2011, at 6:47 PM, Catherine Moore wrote:

[...]

> What I would like to do is add an extension to the scripting language. Something like this:
> 
> MEMORY
> {
>  ram (rwx) : ORIGIN = 0x100000, LENGTH = 144M
> }
> 
> SECTIONS
> {
>  .text : WITHOUT_FLAGS (SHF_PPC_VLE)
>  {
>    *(.text .text.* .gnu.linkonce.t.*)
>  } >ram
>  .text_vle : WITH_FLAGS (SHF_PPC_VLE)
>  {
>    *(.text .text.* .gnu.linkonce.t.*)
>  } >ram
> }
> 
> map_input_to_output_sections would then walk the input sections for those sections with an optional "FLAG" marker.  A callback would be introduced that would examine the ELF header flags for the input sections and gather only those that met the criteria.
> 
> I realize that this is an ELF-centric proposal.  Although it could be extended to include other object formats, I haven't given that aspect alot of thought.
> 
> Before I spend time on development, I'd like to solicit comments ahead of time.  How do the maintainers and others feel about this plan?

I had similar thoughts but for the VMS format, where the section names are less important than their flags.

I think your proposal isn't that ELF-centric: the flags could be a mix of bfd ones (either from section or from file) and target
specific ones.

I also think that you could make the design a little bit generic and allow boolean negation.  What about something like:

 .text : FLAGS (-SHF_PPC_VLE)
 {
   *(.text .text.* .gnu.linkonce.t.*)
 } >ram
 .text_vle : FLAGS (+SHF_PPC_VLE)
 {
   *(.text .text.* .gnu.linkonce.t.*)
 } >ram

That would make the life easier if we later want to add boolean operators (and, or).


Finally I wonder if the flags shouldn't be in the input section part, in order to make this feature even more generic:

.text : 
 {
   *(.text .text.* .gnu.linkonce.t.*) FLAGS (-SHF_PPC_VLE)
 } >ram
 
Tristan.