gobject: try to link with -Wl,-z,nodelete

Since the type system does not support reloading its data and assumes
that libgobject remains loaded for the lifetime of the process, we
should link libgobject with a flag indicating that it can't be unloaded.

https://bugzilla.gnome.org/show_bug.cgi?id=707298

configure.ac

@@ -3468,6 +3468,40 @@ fi
 
 AC_SUBST(GLIB_LINK_FLAGS)
 
+dnl
+dnl Check for -z,nodelete linker flag: the type system assumes that
+dnl libgobject stays loaded for the lifetime of the process.
+dnl Since ld.bfd does not treat wrong -z options as fatal by default,
+dnl we also try to check for the --fatal-warnings linker flag if
+dnl auto-detecting.
+dnl
+
+AC_ARG_ENABLE([znodelete],
+              [AS_HELP_STRING([--disable-znodelete],
+                              [avoid linking with -z,nodelete])],,
+              [SAVED_LDFLAGS="${LDFLAGS}"
+               AC_MSG_CHECKING([for --fatal-warnings linker flag])
+               LDFLAGS=-Wl,--fatal-warnings
+               AC_TRY_LINK([], [int main (void) { return 0; }],
+                           AC_MSG_RESULT(yes)
+                           [ldflags_fatal=-Wl,--fatal-warnings],
+                           AC_MSG_RESULT(no)
+                           ldflags_fatal=)
+               AC_MSG_CHECKING([for -z,nodelete linker flag])
+               LDFLAGS="$ldflags_fatal -Wl,-z,nodelete"
+               AC_TRY_LINK([], [int main (void) { return 0; }],
+                           AC_MSG_RESULT(yes)
+                           enable_znodelete=yes,
+                           AC_MSG_RESULT(no)
+                           enable_znodelete=no)
+               LDFLAGS="${SAVED_LDFLAGS}"])
+
+if test "x${enable_znodelete}" = "xyes"; then
+  GOBJECT_LINK_FLAGS=-Wl,-z,nodelete
+fi
+
+AC_SUBST(GOBJECT_LINK_FLAGS)
+
 dnl
 dnl Check for -fvisibility=hidden to determine if we can do GNU-style
 dnl visibility attributes for symbol export control

gobject/Makefile.am

@@ -45,6 +45,7 @@ endif
 
 libgobjectincludedir = $(includedir)/glib-2.0/gobject
 libgobject_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
+  $(GOBJECT_LINK_FLAGS) \
   $(gobject_win32_res_ldflag) \
   -version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
   -export-dynamic $(no_undefined)