[PATCH] PE-COFF: Fix false positives in auto-export per-library filtering

["Dave Korn" <dave dot korn dot cygwin at googlemail dot com>]

    Afternoon all,

  The attached patch fixes a little hiccup in the auto-export feature of
PE-COFF ld when building DLLs.  If you build a DLL without supplying an
explicit list of exports (in a .DEF file), ld will automatically export all
the public symbols pulled into the final link.

  However, if you're linking the DLL statically against system DLLs or
runtime crtbegin/end objects, re-exporting those symbols would not be what
you want.  To that end, ld filters out symbols belonging to known system
libraries when it's generating the list of auto-exports.

  That's all well and good, but the code that matches against the list of
libraries to filter only uses a leading substring match.  That's ok too,
because we could be linking against a *.a static archive or a *.dll.a import
library, and either way we don't want to re-export the symbols from it.

  But the leading substring match doesn't check that there's any kind of
extension at all immediately after the matching leading part, so it can be
fooled by names that begin the same as a system library.  This happens, for
example, during a build of GCC, when you're compiling libstdc++ as a DLL:
the symbols pulled in from the libtool-generated libsupc++convenience.a
trigger a false match against a filter looking for one of
libsupc++{.a,.dll.a} and the result is that none of the symbols from
libsupc++ gets exported from the final DLL, meaning applications can't link
against them.

  Seems to me the simplest fix is just to extend the leading parts in the
list of filtered libraries so they check there's a period, implying that
there's probably a file extension following.  (Yes, this could still be
fooled by a name like 'libsupc++.convenience.a').  While I was at it, I also
added a new entry for the shared version of libgcc that we're shipping with
Cygwin these days.


2009-12-29  Dave Korn  <dave.korn.cygwin@gmail.com>

	* pe-dll.c (autofilter_liblist):  Add periods to avoid false-positive
	matches on leading substring of library name, and add shared libgcc.


  Ok?

    cheers,
      DaveK

[PS see also outstanding patch
http://sourceware.org/ml/binutils/2008-12/msg00269.html]

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