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From: "amonakov at gmail dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug dynamic-link/28248] is there a way to LD_PRELOAD library before
 other dynamic libraries?
Date: Tue, 31 Aug 2021 17:41:23 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28248

Alexander Monakov <amonakov at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amonakov at gmail dot com

--- Comment #1 from Alexander Monakov <amonakov at gmail dot com> ---
You're mixing up two separate library orderings: the symbol lookup order (w=
hich
is what the man page implicitly refers to, it's breadth-first order over
DT_NEEDED links, with LD_PRELOAD modules appearing just after the main
executable and before its first DT_NEEDED library), and initialization order
(which is reverse topological order over DT_NEEDED links, assuming lack of
cycles).

To interpose malloc and the like, your library needs to appear prior to lib=
c.so
in the former; also, your library in all likelihood depends on libc.so, so =
it
will appear after libc.so in the latter.

The log you've shown confirms this: preload_dump.so is loaded prior to
libtinfo.so.5, but its constructors are invoked last.

ELF gABI document explains this, please have a look:
http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#init_fini

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