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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug build/29456] missing DT_HASH section in shared objects
Date: Mon, 08 Aug 2022 14:45:39 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29456

--- Comment #6 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Arkadiusz Hiler from comment #5)
> (In reply to Florian Weimer from comment #3)
> > Distributions configure or patch GCC to pass --hash-style=3Dgnu to the =
linker
> > by default. The linker default does not matter.
>=20
> Thanks, that explains a few things. My gcc -v indeed claims that:
>=20
>     Configured with: /build/gcc/src/gcc/configure ...
> --with-linker-hash-style=3Dgnu ...
>=20
> 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.
>=20
> Do you know why distros do this?

sysv hashing is much slower for symbol binding because we have to do a strc=
mp
even on lookup failure. The Bloom filter is missing, too. Once the glibc
dynamic linker supported it, I think distributions really wanted to use it,
even if binutils and GCC defaults had not caught up at that point yet. It f=
ixes
real issues around startup performance.

--=20
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