[PATCH libdrm] configure: Support symbol visibility when available

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

Checks whether or not the compiler supports the -fvisibility option. If
so it sets the VISIBILITY_CFLAGS variable which can be added to the per
directory AM_CFLAGS where appropriate.

By default all symbols will be hidden via the VISIBILITY_CFLAGS. The
drm_public macro can be used to mark symbols that should be exported.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
Changes in v3:
- distribute libdrm.h

 Makefile.am  |  1 +
 configure.ac | 20 ++++++++++++++++++++
 libdrm.h     | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 libdrm.h

diff --git a/Makefile.am b/Makefile.am
index 826c30d0c0d9..65680da963eb 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -69,6 +69,7 @@ libdrm_la_SOURCES =				\
 	xf86drmSL.c				\
 	xf86drmMode.c				\
 	xf86atomic.h				\
+	libdrm.h				\
 	libdrm_lists.h
 
 libdrmincludedir = ${includedir}
diff --git a/configure.ac b/configure.ac
index 1c78c4520c49..f7c7177bfb2a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -366,6 +366,26 @@ AC_ARG_WITH([kernel-source],
 	    [kernel_source="$with_kernel_source"])
 AC_SUBST(kernel_source)
 
+dnl Add flags for gcc and g++
+if test "x$GCC" = xyes; then
+    # Enable -fvisibility=hidden if using a gcc that supports it
+    save_CFLAGS="$CFLAGS"
+    AC_MSG_CHECKING([whether $CC supports -fvisibility=hidden])
+    VISIBILITY_CFLAGS="-fvisibility=hidden"
+    CFLAGS="$CFLAGS $VISIBILITY_CFLAGS"
+    AC_LINK_IFELSE([AC_LANG_PROGRAM()], AC_MSG_RESULT([yes]),
+                   [VISIBILITY_CFLAGS=""; AC_MSG_RESULT([no])]);
+
+    # Restore CFLAGS; VISIBILITY_CFLAGS are added to it where needed.
+    CFLAGS=$save_CFLAGS
+
+    if test "x$VISIBILITY_CFLAGS" != x; then
+        AC_DEFINE(HAVE_VISIBILITY, 1, [Compiler has -fvisibility support])
+    fi
+
+    AC_SUBST([VISIBILITY_CFLAGS])
+fi
+
 AC_SUBST(WARN_CFLAGS)
 AC_CONFIG_FILES([
 	Makefile
diff --git a/libdrm.h b/libdrm.h
new file mode 100644
index 000000000000..23926e6f6741
--- /dev/null
+++ b/libdrm.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright © 2014 NVIDIA Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef LIBDRM_LIBDRM_H
+#define LIBDRM_LIBDRM_H
+
+#if defined(HAVE_VISIBILITY)
+#  define drm_private __attribute__((visibility("hidden")))
+#  define drm_public __attribute__((visibility("default")))
+#else
+#  define drm_private
+#  define drm_public
+#endif
+
+#endif
-- 
2.0.3