[PATCH] ELF: Properly handle section symbols

[H.J. Lu]

On Tue, Jun 9, 2020 at 9:42 PM Alan Modra <amodra@gmail.com> wrote:
>
> On Tue, Jun 09, 2020 at 11:50:23AM -0700, H.J. Lu wrote:
> > When defining the section symbol, __start_FOO, for the section FOO:
> >
> > 1. Treat the common symbol, __start_FOO, in input object file as
> > definition.
> > 2. Clear verinfo.verdef.
>
> The above looks good.
>
> > 3. Make the section symbol PROTECTED only in shared library.
>
> I would be inclined to not make this change.  While it is true that
> protected visibility only makes sense in a shared library, I can't see
> a compelling reason to prohibit such a symbol in an executable.  I

This is a quality of implementation issue.  I will create a separate patch
for it.

> made the comment in the bugzilla
> "But that leaves you with a really odd
>      5: 0000000000004010     8 OBJECT  GLOBAL PROTECTED   24 __start_FOO@@SOME_VERSION_NAME
> in main."
> because it seemed to me that this symbol being dynamic in the
> executable serves no purpose.  The dynamic symbol of the same name in

It is to support dlopen (section_symbol).

> libfoo.so, being protected visibility, can't be overridden by a symbol
> in the executable.
>
> Trimming off unnecessary dynamic symbols like this one is probably
> best not done just before a binutils release.

That will break some applications.

This is the patch I am checking in.

-- 
H.J.
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