From f46cbf6b0865d1df7676e114f94a09a4be7c1b58 Mon Sep 17 00:00:00 2001
From: Philip Withnall <withnall@endlessm.com>
Date: Mon, 13 Feb 2017 11:46:59 +0000
Subject: [PATCH] gmodule: Add the visibility attribute to G_MODULE_EXPORT on
 gcc
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For versions of GCC which support it (≥ 4), define G_MODULE_EXPORT as
__attribute__((visibility("default"))). This is normally a no-op, unless
compiling with -fvisibility=hidden, in which case it marks a symbol to
be publicly exported from the library, which is what G_MODULE_EXPORT is
for. Previously G_MODULE_EXPORT has only worked on Windows.

The compatibility check for whether the compiler supports
__attribute__((visibility)) is based on the __GNUC__ define, and is
similar to the check done in configure.ac for defining G_GNUC_INTERNAL.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=778287
---
 gmodule/gmodule.c | 12 +++++++++---
 gmodule/gmodule.h |  4 +++-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/gmodule/gmodule.c b/gmodule/gmodule.c
index f02dbbca5..a5da99179 100644
--- a/gmodule/gmodule.c
+++ b/gmodule/gmodule.c
@@ -167,9 +167,15 @@
 /**
  * G_MODULE_EXPORT:
  *
- * Used to declare functions exported by modules. This is a no-op on Linux
- * and Unices, but when compiling for Windows, it marks a symbol to be
- * exported from the library or executable being built.
+ * Used to declare functions exported by libraries or modules.
+ *
+ * When compiling for Windows, it marks the symbol as `dllexport`.
+ *
+ * When compiling for Linux and Unices, it marks the symbol as having `default`
+ * visibility. This is no-op unless the code is being compiled with a
+ * non-default
+ * [visibility flag](https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#index-fvisibility-1260)
+ * such as `hidden`.
  */
 
 /**
diff --git a/gmodule/gmodule.h b/gmodule/gmodule.h
index 194fa6e69..aa98f00d2 100644
--- a/gmodule/gmodule.h
+++ b/gmodule/gmodule.h
@@ -35,7 +35,9 @@ G_BEGIN_DECLS
 #define	G_MODULE_IMPORT		extern
 #ifdef G_PLATFORM_WIN32
 #  define	G_MODULE_EXPORT		__declspec(dllexport)
-#else /* !G_PLATFORM_WIN32 */
+#elif __GNUC__ >= 4
+#  define	G_MODULE_EXPORT		__attribute__((visibility("default")))
+#else /* !G_PLATFORM_WIN32 && __GNUC__ < 4 */
 #  define	G_MODULE_EXPORT
 #endif /* !G_PLATFORM_WIN32 */