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Re: [PATCH] Implement a command line switch to prevent section GC from removing exported symbols

On Wed, Dec 14, 2016 at 05:25:38PM +0100, fincs fincs wrote:
> On Wed, Dec 14, 2016 at 4:45 AM, Alan Modra <> wrote:
> >
> > Why doesn't --export-dynamic work for you?
> >
> Thank you for your suggestion. But first, let me better explain my
> current situation. I am building a program for an embedded device that
> runs directly on bare metal and I am not targeting an OS (my toolchain
> is aarch64-none-elf). However I'd like to process the ELF executable
> before being converted to raw binary format with a custom tool to save
> the values of all default-visibility (i.e. exported) symbols for use
> by several other additional components that will also run on bare
> metal (but they aren't immediately loaded in). Using --export-dynamic
> indeed makes sure that all default-visibility symbols stay in the
> executable even if they are not referenced, however it also outputs a
> full ELF .dynamic section with many other ancillary sections. Since
> there is no dynamic linker under the hood nor anything else that may
> need to use those sections, I'd prefer not to include them in the
> final binary since they take up unnecessary space (also part of the
> reason why I'm using --gc-sections). The alternatives that currently
> exist involve explicitly listing all symbols to keep, which seems
> inelegant and unmaintainable to me, especially in the cases where
> there may be hundreds of symbols to export.

Thanks for the explanation.  That all makes sense, and the patch looks
reasonable.  It just lacks a ChangeLog and ld.texinfo documentation.
The documentaion should mention that the option is for executables and
that it keeps default and protected visibility defined global symbols
and their sections.

Alan Modra
Australia Development Lab, IBM

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