Re: Specifying LMA's after unallocated sections?

[Jonathan Larmour <jlarmour at redhat dot co dot uk>]

Ian Lance Taylor wrote:
>    .foo 0x1000 : AT 0xf000 { *(.foo) }
>    .bar 0x2000 : AT (LOADADDR(.foo) + SIZEOF(.foo)) { *(.bar) }
> 
>    So .bar follows .foo in e.g. a ROM image, but they get relocated to
>    different places.
> 
>    But what happens if there are no .foo input sections? Then the section
>    doesn't get defined and both LOADADDR(.foo) and SIZEOF(.foo) are
>    invalid.
> 
> The right way to do it is to patch the linker so that if an output
> section is mentioned in a LOADADDR or SIZEOF construct, it gets
> created even if it has no input sections.  This basically means
> calling init_os for the right sorts of constructs.
> 
> It could be as simple as putting
>   if (s->load_base != NULL)
>     exp_init_os (s->addr_tree);
> at the end of init_os().

I was thinking of some way to avoid outputting the section regardless.
Suppose for example you want to put .bar after .rel.* relocation
information. I know (because I accidentally stumbled across it) that
outputting an empty .rel section makes BFD very unhappy. And to be honest,
I think BFD is right: you shouldn't be emitting "unused" empty output
sections in general.

Jifl
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