Re: Linker Bug or Design Intent (Absolute symbols in zero sized sections)

["H. J. Lu" <hjl@lucon.org>]

On Tue, Sep 26, 2006 at 11:06:19AM -0400, Vivek Goyal wrote:
> Daniel Jacobowitz wrote:
> >On Tue, Sep 26, 2006 at 07:51:59AM -0700, H. J. Lu wrote:
> >
> >>I think for --emit-relocs, we can keep an empty output section if its
> >>address is taken.
> >>
> >>Of course, we need to update linker doc.
> >
> >
> >I think we're being too specific to this case.
> >
> >Why are we changing what the linker script clearly defines as section
> >relative symbols to absolute symbols?  This isn't the only use case
> >I've encountered where that will break.  We should either discard the
> >symbols, or leave the empty section.
> >
> 
> I think retaining the zero sized section might be more logical otherwise 
> a user who has specifically defined a section relative symbol in linker 
> script file will be surprised to know that in some cases symbol is not 
> present at all.


I think removing empty output sections isn't a bad idea. Otherwise,
a normal executable/DSO may have many empty output sections since
the default linker scripts may have many unused output sections.

However, I agree that removing empty output sections shouldn't lead
to many surprises for user. I think linker

1. Should remove an empty output section if it isn't used to define
section relative symbol which may be changed at run time.
2. Shouldn't convert a section relative symbol to absolute symbol
if it may be changed at run time.
3. Should preserve the pre-set constant VMA of an empty output section.

Is there anything I missed?


H.J.