On Dienstag, 13. August 2013 08:26:51 CEST, Pali Rohár wrote:
On Monday 12 August 2013 22:36:26 Jan Kundrát wrote:
They way I understand it, Pali wants to support a
configuration where there are no shared libraries, just the
/usr/bin/trojita with some plugins statically linked in.
Yes, I want to support also this configuration. But not only this.
No. Runtime loading should work too (at least with GCC). For GNU
compiler/linker is needed special flag, but this is added by cmake
when using GNU. Also if some password and some addressbook
plugins will be statically linked into trojita executable, it
will not be needed anymore.
Runtime symbol resolution is performed by RTDL_* - it should not be affected
here.
The reason why Pali (likely) needs -whole-archive is because otherwise the
unreferenced objects in the plugins will not be resolved / included.
I doubt that it's implicit impact on symbol resolution (precendence of static
linked libs) is any important here. (Please fix me, if i missed sth. obvious,
but sane symbol resolution is done differently anyway)
---
Pretending this is a reasonable target:
============================
a) -whole-archive is not specific to GCC, but GNU ld - no matter which compiler
invokes it, so that should be tested instead.
b) the equivalent on CLANG is -force_load <library>, MSVC has /INCLUDE [1] and
/OPT:NOREF [2] - no guarantee that it works at all (One could look up the dsp's for
Qt)
c) simply DO NOT DO THAT.
---------------------
If you want to compile in plugins, just instantiate the objects based on the
plugin name, like
if (pluginName == "ClearTextPassword")
plugin = new ClearTextPassword;
else if (pluginName == "AkonadiAddressbook")
plugin = new AkonadiAddressbook;
else if () ...
else {
// attempt to dlopen plugin library here
}
This will get you the relevant objects referenced and added to the binary by
all compilers that are the least ISO compliant.
And it requires one preprocessor block and CFLAG only.
It will also prevent unneeded bloat (in case there's irrelevant stuff in the
lib you link in this way) and not be acidentally broken by downstream, tweaking
compiler options for optimization.
Cheers,
Thomas
[1] http://msdn.microsoft.com/en-us/library/2s3hwbhs(v=VS.100).aspx
[2] http://msdn.microsoft.com/en-US/library/bxwfs976(v=VS.80).aspx
