libnotmuch: export Xapian typeinfo symbols

The lack of such exporting seems to cause problems catching
exceptions, as suggested by

    http://gcc.gnu.org/wiki/Visibility

This manifested in the symbol-hiding test failing when notmuch was
compile with gcc 4.4.5. On i386, this further manifested as notmuch
new failing to run (crashing with an uncaught exception on first run).

lib/Makefile.local

@@ -76,9 +76,7 @@ $(dir)/$(LIBNAME): $(libnotmuch_modules) notmuch.sym
 	$(call quiet,CXX $(CXXFLAGS)) $(libnotmuch_modules) $(FINAL_LIBNOTMUCH_LDFLAGS) $(LIBRARY_LINK_FLAG) -o $@
 
 notmuch.sym: lib/notmuch.h
-	printf "{\nglobal:\n" > notmuch.sym
+	sh lib/gen-version-script.sh $< $(libnotmuch_modules) > $@
-	sed  -n 's/^\s*\(notmuch_[a-z_]*\)\s*(.*/\t\1;/p' $< >> notmuch.sym
-	printf "local: *;\n};\n" >> notmuch.sym
 
 $(dir)/$(SONAME): $(dir)/$(LIBNAME)
 	ln -sf $(LIBNAME) $@

lib/gen-version-script.sh

@@ -0,0 +1,27 @@
+
+# we go through a bit of work to get the unmangled names of the
+# typeinfo symbols because of
+# http://sourceware.org/bugzilla/show_bug.cgi?id=10326
+
+if [ $# -lt 2 ]; then
+    echo Usage: $0 header obj1 obj2 obj3
+    exit 1;
+fi
+
+HEADER=$1
+shift
+
+printf '{\nglobal:\n'
+nm --defined $* | awk '$3 ~ "Xapian.*Error" {print $3}' | sort | uniq | \
+while read sym; do
+    demangled=$(c++filt $sym)
+    case $demangled in
+	typeinfo*) 
+	    printf "\t$sym;\n"
+	    ;;
+	*)
+	    ;;
+    esac
+done
+sed  -n 's/^\s*\(notmuch_[a-z_]*\)\s*(.*/\t\1;/p' $HEADER
+printf "local: *;\n};\n"