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From: gjb@cs.brown.edu (Gregory Brail)
Newsgroups: comp.lang.c++
Subject: SunOS shared libraries and virtual tables
Message-ID: <68989@brunix.UUCP>
Date: 18 Mar 91 21:48:42 GMT
Sender: news@brunix.UUCP
Reply-To: gjb@cs.brown.edu (Gregory Brail)
Organization: Brown University Department of Computer Science
Lines: 33

In SunOS, one can make libraries "shared," which means their code in
memory is shared between all processes that use them, and all those
executables use the same file to get at the code. However, external
initialized data (like global constants, for instance) cannot be
shared. One can, however, manually put all external initialized data
in a separate part of the library so it won't be shared and the rest
of the library will be.

With C, this is easy. With C++, however, all virtual tables and
pointers to virtual tables fall under the "external initialized data"
category, or at least that's how I understand it.

Has anyone come up with a good way to solve this problem? One can just
ignore the problem with virtual tables -- the shared libraries still
work (although less efficiently). One could also use the +e0 and +e1
arguments to cfront by creating one (or a few) files that contain just
class definitions and putting those definitions in the non-shared part
of the library. This, however, is a pain, and getting a few hundred
class definitions into one file isn't easy, to say the least.

The shared version of libC that comes with Sun C++ appears to have the
virtual tables in the sharable portion of the library. Is this the
correct solution, or should one put the virtual tables in the
non-shared portion? And if that's the case, what's the easiest way to
do that?

Thanks in advance for the help.

				-greg
+----------------------------------------------------+
Greg Brail
Internet: gjb@cs.brown.edu  BITNET: gjb@browncs.bitnet
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