openbscdefines.h: Add header file to control visibility of symbols

Add the hooks/configure detection to compile everything with
-fvisibility=hidden and then make certain symbols visible. This
will be used to make parts of the API public.
There are no users yet but we should have some soon.

configure.in

@@ -18,6 +18,21 @@ AC_HEADER_STDC
 
 dnl Checks for typedefs, structures and compiler characteristics
 
+# The following test is taken from WebKit's webkit.m4
+saved_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -fvisibility=hidden "
+AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
+AC_COMPILE_IFELSE([char foo;],
+      [ AC_MSG_RESULT([yes])
+        SYMBOL_VISIBILITY="-fvisibility=hidden"],
+        AC_MSG_RESULT([no]))
+CFLAGS="$saved_CFLAGS"
+AC_SUBST(SYMBOL_VISIBILITY)
+
+
+dnl Generate the output
+AM_CONFIG_HEADER(bscconfig.h)
+
 AC_OUTPUT(
     openbsc.pc
     include/openbsc/Makefile

include/openbsc/Makefile.am

@@ -2,4 +2,4 @@ noinst_HEADERS = abis_nm.h abis_rsl.h debug.h db.h gsm_04_08.h gsm_data.h \
 		 gsm_subscriber.h linuxlist.h msgb.h select.h tlv.h gsm_04_11.h \
 		 timer.h misdn.h chan_alloc.h telnet_interface.h paging.h \
 		 subchan_demux.h trau_frame.h e1_input.h trau_mux.h signal.h \
-		 gsm_utils.h ipaccess.h rs232.h
+		 gsm_utils.h ipaccess.h rs232.h openbscdefines.h

include/openbsc/openbscdefines.h

@@ -0,0 +1,35 @@
+/* 
+ * (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef OPENBSCDEFINES_H
+#define OPENBSCDEFINES_H
+
+#ifdef BUILDING_ON_WINDOWS
+    #ifdef BUILDING_OPENBSC
+        #define BSC_API __declspec(dllexport)
+    #else
+        #define BSC_API __declspec(dllimport)
+    #endif
+#else
+    #define BSC_API __attribute__((visibility("default")))
+#endif
+
+#endif