[Bug build/29456] missing DT_HASH section in shared objects

["arek at hiler dot eu" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29456

--- Comment #5 from Arkadiusz Hiler <arek at hiler dot eu> ---
(In reply to Florian Weimer from comment #3)
> Distributions configure or patch GCC to pass --hash-style=gnu to the linker
> by default. The linker default does not matter.

Thanks, that explains a few things. My gcc -v indeed claims that:

    Configured with: /build/gcc/src/gcc/configure ...
--with-linker-hash-style=gnu ...

According to gcc/docs/install.texi the default is sysv but after browsing
the code for a bit it looks like if `--with-linker-hash-style` is not
specified no `--hash-style` is passed to the linker so it would depend on
linker's defaults.

Do you know why distros do this? Looking at package history it seems like an
artifact from the times where both was a bit problematic. There used to be
some custom patches for that years ago.


(In reply to Adhemerval Zanella from comment #4)
> > This breaks all the games running via Proton that are using EAC.
> 
> What EAC is doing exactly that requires a DT_HASH on glibc? What happens if
> you mix DT_HASH and DT_GNU_HASH shared objects (for instance shared
> libraries with only one option)? It does seem a shortcoming from EAC,
> although I am not sure what exactly it is trying to enforce here.

I can only guess but probably to look up some symbols in multiple ways to
assure no hooking has occurred.

It seems to require it only for the glibc DSOs as they were shipping with
DT_HASH for years, even on distros that default to gnu, and this is an
unexpected change.

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