bug#45676: Store references inside compressed data

[Leo Famulari]

On Tue, Jan 05, 2021 at 03:36:07PM +0100, Miguel Ángel Arruga Vivas wrote:
> There are several binary formats that allow compression of the
> executable image, or some of its data, which is decompress at runtime:
> 
>   - Kernel images.
>   - Compressed libraries: e.g. Smalltalk modules.
>   - Compressed executable or data files: e.g. library.el.gz.
> 
> These aren't taken into account by the grafting process, which may lead
> to issues when store paths are located inside that kind of files.

It's a serious problem, and not just because of grafting. These obscured
references can cause things to be garbage collected inappropriately.

Here is an older case of the same problem:

https://bugs.gnu.org/24703

It was resolved by patching GCC.