[patch] ld: PE: comprehensive auto-filtering for DLL-exportable symbols

[Paul Sokolovsky <paul-ml at is dot lg dot ua>]

Hello binutils,

  This is a followup to recent thread concerning how "auto-export"
works for PE DLLs. To remind, ld has "auto-export" feature which
allows DLLs built from a set of object files automagically export all
symbols - just the same as standard *nix shared libraries work -
instead of using win32 idiosyncrasy of listing each symbols in .def
file or marking it with __declspec(dllexport) in the source code.

   Unfortunately, auto-export used to work not very well due to
different shortcoming, one of which was recently raised on this list:
it is too much being exported with it. This is not aesthetical, waste
space in export section, and sometimes even impedes linking against
such library due to duplicate symbols. I addressed this problem
several months ago, and since that binutils with changes proposed
were available for testing at http://sourceforge.net/projects/mingw/ .

   Attached patch got its shape in several iterations, as I was
understanding that adequate filtering was not possible with just
pattern filtering of symbol names. So, it uses several heuristics to
achieve adequate effect:

1. Pattern filtering of symbol names (leave out bunch of startup
   symbols, import thunks, C++ internal stuff like __rtti_*, etc.)
2. Pattern filtering plus querying symbol table (do not re-export
   symbols which were imported from other DLL, i.e. exist only as
   the thunks in the object being produced)
3. Contextual filtering by containing library name (no need to export
   anything coming from predefined libraries like libgcc or
   libstdc++).

   For more discussion and effects of this patch, see
http://cygwin.com/ml/cygwin/2000-11/msg00242.html . Hope this
description was comprehensive enough to support the patch.


2001-04-29  Paul Sokolovsky  <Paul.Sokolovsky@technologist.com>

        * pe-dll.c (auto_export): Pass the bfd containing symbol
        being checked to the function; perform careful filtering
        of exportable symbols, do not export: more auxilary symbols
        (including startup, C++-internal, DLL-layout symbols, etc.),
        symbols imported from DLLs, symbols from several predefined
        libraries (like libgcc/libstdc++).



--
Paul Sokolovsky, IT Specialist
http://www.brainbench.com/transcript.jsp?pid=11135

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