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Date: Mon, 05 Sep 2011 07:50:00 -0000
Message-ID: <CAF+LTeddhPLYLvYaLM=X3N4F_0UMrk_nTGP=zdZimY_aVUUK7g@mail.gmail.com>
Subject: [PLUGIN] dlopen and RTLD_NOW
From: Romain Geissler <romain.geissler@gmail.com>
To: gcc@gcc.gnu.org
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Hi

Is there any particular reason to load plugin with the RTLD_NOW option?
This option force .so symbol resolution to be completely made at load time,
but this could be done only when a symbol is needed (RTLD_NOW).

Here is the dlopen line in plugin.c:
dl_handle = dlopen (plugin->full_name, RTLD_NOW | RTLD_GLOBAL);

My issue is, I want to load the same plugin.so in both cc1 and cc1plus, but
in the C++ case, I may need to reference some cc1plus specific symbols. I can
check whether cc1 or cc1plus loaded the plugin and thus use custom C++
symbols only when present. With RTLD_NOW, the plugin fails to load in cc1 as
symbol resolution is forced at load time.

If RTLD_NOW is removed, dlopen falls back to the RTLD_LAZY mode which fits
my need. Moreover, if one can force the complete symbol resolution at load time
by defining the environment LD_BIND_NOW variable.

So, is RTLD_NOW use justified ?

Romain Geissler