Date: Sat, 03 Feb 1996 10:17:53 -0800 From: John Polstra <jdp@polstra.com> To: Peter Wemm <peter@jhome.DIALix.COM> Cc: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>, bde@zeta.org.au (Bruce Evans), CVS-committers@freebsd.org, cvs-lib@freebsd.org, nate@sri.MT.net Subject: Re: cvs commit: src/lib/csu/i386 crt0.c Message-ID: <199602031817.KAA00907@austin.polstra.com> In-Reply-To: Your message of "Sun, 04 Feb 1996 00:48:29 %2B0800." <199602031648.AAA25239@jhome.DIALix.COM>
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Peter wrote:
> It seems that linker_sets are not constructed at run-time by the
> dynamic linker.. (although I could be wrong)
It's not the dynamic linker's responsibility to do anything with the
linker sets. The dynamic linker's only responsibilities in that
regard are:
1. Upon loading a shared library, call its function named (in C)
"_init", if one exists. (For backward compatibility, the
assembly-language name ".init" is also OK.)
2. Upon unloading a shared library, call its function named "_fini",
if one exists. (For backward compatibility, the
assembly-language name ".fini" is also OK.)
If anything needs to be done with linker sets, then the "_init"
and "_fini" functions have to take care of it. The functions
provided by /usr/lib/c++rt0.o do exactly that.
> Why can't we use a c++ style constructor?
Yes, that's the right way to do it. See Christopher Provenzano's Feb 1
(in the US) posting to cvs-committers, cvs-lib, and cvs-all, and my reply
to it.
> all gcc supplied "main()" code contains calls to __main() in
> libgcc.a.
Be careful here, it's tricky. The __main() cruft is used only for
invoking the static constructors in the main program itself -- *not* for
those in any shared library. In other words, constructors in the main
executable are invoked by __main(), but those in shared libraries are
invoked by _init(), which is called automatically by the dynamic linker.
They're two separate mechanisms.
Since the initialization that needs to be done is an integral part of
the shared libc library, __main() should not get involved at all.
Instead, /usr/lib/c++rt0.o should be linked into the shared version of
libc, by defining CPLUSPLUSLIB (sigh) in its Makefile. Don't do that
until you've really got at least one constructor in there to call,
though. Otherwise, you'll run into the recent bug that caused
mysterious failures in awk and other programs. (I know how to fix it,
but I haven't figured out how to bootstrap it into a make world.)
For the case of the static libc.a, anything used from the library *is*
part of the main executable. So in that case, __main() will invoke the
static constructors and destructors.
> This is, of course, assuming that c++ constructors in dynamic loaded
> shared libs is "working"....
They work perfectly fine, since well before the 2.1 release.
-- John
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