From 10cb6155670a2a7b51356ada16206564cff748e2 Mon Sep 17 00:00:00 2001
From: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Date: Mon, 6 Aug 2012 18:16:58 +0200
Subject: [PATCH] configure: check for visibility attribute.

Add a check for GCC "visibility" attribute. Also define DLL_HIDDEN helper
so that to declare functions as internal to a particular shared library.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
---
 configure.ac | 22 ++++++++++++++++++++++
 va/sysdeps.h |  8 ++++++++
 2 files changed, 30 insertions(+)

diff --git a/configure.ac b/configure.ac
index 7f7f9af..72eac8e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -171,6 +171,28 @@ if test "$enable_docs" = "yes"; then
 fi
 AM_CONDITIONAL(ENABLE_DOCS, test "$enable_docs" = "yes")
 
+# Check for __attribute__((visibility()))
+AC_CACHE_CHECK([whether __attribute__((visibility())) is supported],
+    ac_cv_have_gnuc_visibility_attribute,
+    [cat > conftest.c <<EOF
+int foo __attribute__ ((visibility ("hidden"))) = 1;
+int bar __attribute__ ((visibility ("protected"))) = 1;
+EOF
+    ac_cv_have_gnuc_visibility_attribute="no"
+    if ${CC-cc} -Werror -S conftest.c -o conftest.s >/dev/null 2>&1; then
+        if grep '\.hidden.*foo' conftest.s >/dev/null; then
+            if grep '\.protected.*bar' conftest.s >/dev/null; then
+                ac_cv_have_gnuc_visibility_attribute="yes"
+            fi
+        fi
+    fi
+    rm -f conftest.[cs]
+])
+if test "$ac_cv_have_gnuc_visibility_attribute" = "yes"; then
+    AC_DEFINE([HAVE_GNUC_VISIBILITY_ATTRIBUTE], [1],
+              [Defined to 1 if GCC visibility attribute is supported])
+fi
+
 # Check for X11
 USE_X11="no"
 if test "$enable_x11" = "yes"; then
diff --git a/va/sysdeps.h b/va/sysdeps.h
index 2ab37e9..77db28a 100644
--- a/va/sysdeps.h
+++ b/va/sysdeps.h
@@ -42,4 +42,12 @@
 # define False 0
 #endif
 
+#if defined __GNUC__ && defined HAVE_GNUC_VISIBILITY_ATTRIBUTE
+# define DLL_HIDDEN __attribute__((visibility("hidden")))
+# define DLL_EXPORT __attribute__((visibility("default")))
+#else
+# define DLL_HIDDEN
+# define DLL_EXPORT
+#endif
+
 #endif /* SYSDEPS_H */
-- 
2.7.4