Darwin fix libstdc++ build warnings.

GCC does not export construction vtable symbols from shared libraries.

The symbols are marked hidden in the objects; for Darwin that makes
them also external (“private_extern” is Darwin’s hidden) which means
that they show up in the list of possible symbols for export from
libstdc++, and there are sufficiently relaxed match conditions that
they reach the exports list.   When Darwin’s static linker encounters
them it generates a warning that they cannot be exported.  This patch
prunes them from the list of symbols to be considered, thus
eliminating the warnings. No functional Change inended to the library
exports.

2018-12-06  Iain Sandoe  <iain@sandoe.co.uk>

	* scripts/make_exports.pl (check names): Don’t try to export
	construction vtable symbols.

From-SVN: r266864

libstdc++-v3/ChangeLog

+2018-12-06  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* scripts/make_exports.pl (check names): Don’t try to export
+	construction vtable symbols.
+
 2018-12-06  Jonathan Wakely  <jwakely@redhat.com>
 	    Iain Sandoe  <iain@sandoe.co.uk>
 

libstdc++-v3/scripts/make_exports.pl

@@ -103,6 +103,14 @@ NAME: while (<NM>) {
     # Ignore undefined and local symbols.
     next if (/^([^ ]+) [Ua-z] /);
 
+    # GCC does not export construction vtables from shared libraries.
+    # However the symbols are marked hidden, for Darwin that makes them
+    # also external "private_extern", which means that they show up in
+    # this list.  When ld64 encounters them it generates a warning that
+    # they cannot be exported, so trim them from the set now.
+    next if (/^construction vtable.*$/);
+    next if (/^__ZTC.*$/);
+
     # $sym is the name of the symbol, $noeh_sym is the same thing with
     # any '.eh' suffix removed.
     die "unknown nm output $_" if (! /^([^ ]+) [A-Z] /);