Use -fvisibility=hidden by default on Unix

Now that we have all symbols annotated as GLIB_PUBLIC, we can switch
the build to default to hiding symbols.  The major advantage of this
is that it's much harder to accidentally leak symbols.

This patch only adds it to CFLAGS for the sublibraries; we don't want
to affect things like gio/fam, nor the executables.

However, this patch only changes Unix - on Windows, we keep the
.symbols file because we still ultimately need a .def file in order to
generate a .dll.

To unify both Unix and Windows again, we need to do what cairo does
and parse the headers at build time.

https://bugzilla.gnome.org/show_bug.cgi?id=688681

configure.ac

@@ -858,6 +858,12 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#if defined(__SUNPRO_C) || (__SUNPRO_C >= 0
 AC_MSG_RESULT($g_have_sunstudio_visibility)
 AM_CONDITIONAL(HAVE_SUNSTUDIO_VISIBILITY, [test x$g_have_sunstudio_visibility = xyes])
 
+dnl See https://bugzilla.gnome.org/show_bug.cgi?id=688681
+dnl First half of symbol visibility; search for "Second half of symbol
+dnl visibility" below to find the second part.
+AS_IF([test x$g_have_gnuc_visibility = x && test x$g_have_sunstudio_visibility = x], [
+  AC_MSG_ERROR([GLib does not know how to control symbol visibility on this platform])])
+
 # check for bytesex stuff
 AC_C_BIGENDIAN
 if test x$ac_cv_c_bigendian = xuniversal ; then
@@ -3532,6 +3538,17 @@ fi
 
 AC_SUBST(GLIB_LINK_FLAGS)
 
+dnl See https://bugzilla.gnome.org/show_bug.cgi?id=688681
+dnl Second half of symbol visibility; search for "First half of symbol
+dnl visibility" above to find the first part.  They are separated for
+dnl the same reason the -Werror bits below are last - so we don't affect
+dnl any autoconf tests.
+GLIB_HIDDEN_VISIBILITY_CFLAGS=""
+AS_IF([test x$GCC = xyes], [GLIB_HIDDEN_VISIBILITY_CFLAGS="-fvisibility=hidden"],
+      [test x$g_have_sunstudio_visibility != x], [GLIB_HIDDEN_VISIBILITY_CFLAGS="-xldscope=hidden"],
+      [AC_MSG_ERROR([GLib does not know how to make symbols hidden by default with this compiler])])
+AC_SUBST(GLIB_HIDDEN_VISIBILITY_CFLAGS)
+
 dnl Compiler flags; macro originates from systemd
 dnl See https://bugzilla.gnome.org/show_bug.cgi?id=608953
 CC_CHECK_FLAGS_APPEND([with_cflags], [CFLAGS], [\

gio/Makefile.am

@@ -10,6 +10,8 @@ SUBDIRS += xdgmime
 endif
 
 if OS_WIN32_AND_DLL_COMPILATION
+gio_def = gio.def
+export_symbols = -export-symbols $(gio_def)
 if MS_LIB_AVAILABLE
 noinst_DATA = gio-2.0.lib
 
@@ -507,18 +509,19 @@ install-data-local: install-ms-lib install-def-file
 
 uninstall-local: uninstall-ms-lib uninstall-def-file
 
+libgio_2_0_la_CFLAGS = $(AM_CFLAGS) $(GLIB_HIDDEN_VISIBILITY_CFLAGS)
 libgio_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
 	$(gio_win32_res_ldflag) \
 	-version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
-	-export-dynamic $(no_undefined) -export-symbols gio.def
+	-export-dynamic $(no_undefined) $(export_symbols)
 
 if OS_COCOA
 # This is dumb.  The ObjC source file should be properly named .m
-libgio_2_0_la_CFLAGS = -xobjective-c
+libgio_2_0_la_CFLAGS += -xobjective-c
 libgio_2_0_la_LDFLAGS += -Wl,-framework,Foundation
 endif
 
-libgio_2_0_la_DEPENDENCIES = $(gio_win32_res) gio.def $(platform_deps)
+libgio_2_0_la_DEPENDENCIES = $(gio_win32_res) $(gio_def) $(platform_deps)
 
 gio-win32-res.o: gio.rc
 	$(WINDRES) gio.rc $@

glib/Makefile.am

@@ -90,6 +90,8 @@ BUILT_EXTRA_DIST = 		\
 lib_LTLIBRARIES = libglib-2.0.la
 
 if OS_WIN32_AND_DLL_COMPILATION
+glib_def = glib.def
+export_symbols = -export-symbols $(glib_def)
 if MS_LIB_AVAILABLE
 noinst_DATA = glib-2.0.lib
 
@@ -365,13 +367,14 @@ pcre_lib = pcre/libpcre.la
 pcre_inc =
 endif
 
+libglib_2_0_la_CFLAGS = $(AM_CFLAGS) $(GLIB_HIDDEN_VISIBILITY_CFLAGS)
 libglib_2_0_la_LIBADD = libcharset/libcharset.la $(printf_la) @GIO@ @GSPAWN@ @PLATFORMDEP@ @ICONV_LIBS@ @G_LIBS_EXTRA@ $(pcre_lib) $(G_THREAD_LIBS_EXTRA) $(G_THREAD_LIBS_FOR_GTHREAD)
-libglib_2_0_la_DEPENDENCIES = libcharset/libcharset.la $(printf_la) @GIO@ @GSPAWN@ @PLATFORMDEP@ $(glib_win32_res) glib.def
+libglib_2_0_la_DEPENDENCIES = libcharset/libcharset.la $(printf_la) @GIO@ @GSPAWN@ @PLATFORMDEP@ $(glib_win32_res) $(glib_def)
 
 libglib_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
 	 $(glib_win32_res_ldflag) \
 	-version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
-	-export-dynamic $(no_undefined) -export-symbols glib.def
+	-export-dynamic $(no_undefined) $(export_symbols)
 
 INSTALL_PROGS=
 

gmodule/Makefile.am

@@ -65,6 +65,8 @@ no_undefined = -no-undefined
 endif
 
 if OS_WIN32_AND_DLL_COMPILATION
+gmodule_def = gmodule.def
+export_symbols = -export-symbols $(gmodule_def)
 gmodule_win32_res = gmodule-win32-res.o
 gmodule_win32_res_ldflag = -Wl,$(gmodule_win32_res)
 
@@ -78,12 +80,13 @@ install-def-file:
 uninstall-def-file:
 endif
 
+libgmodule_2_0_la_CFLAGS = $(AM_CFLAGS) $(GLIB_HIDDEN_VISIBILITY_CFLAGS)
 libgmodule_2_0_la_SOURCES = gmodule.c
 libgmodule_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
 	$(gmodule_win32_res_ldflag) \
 	$(G_MODULE_LDFLAGS) \
 	-version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
-	-export-dynamic $(no_undefined) -export-symbols gmodule.def
+	-export-dynamic $(no_undefined) $(export_symbols)
 
 libgmodule_2_0_la_LIBADD = $(G_MODULE_LIBS_EXTRA) $(G_MODULE_LIBS) $(libglib)
 

gobject/Makefile.am

@@ -30,6 +30,8 @@ libglib = $(top_builddir)/glib/libglib-2.0.la
 lib_LTLIBRARIES = libgobject-2.0.la
 
 if OS_WIN32_AND_DLL_COMPILATION
+gobject_def = gobject.def
+export_symbols = -export-symbols $(gobject_def)
 if MS_LIB_AVAILABLE
 noinst_DATA = gobject-2.0.lib
 
@@ -67,13 +69,13 @@ libgobjectincludedir = $(includedir)/glib-2.0/gobject
 libgobject_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
   $(gobject_win32_res_ldflag) \
   -version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
-  -export-dynamic $(no_undefined) -export-symbols gobject.def
+  -export-dynamic $(no_undefined) $(export_symbols)
 
-libgobject_2_0_la_CFLAGS = $(LIBFFI_CFLAGS)
+libgobject_2_0_la_CFLAGS = $(AM_CFLAGS) $(LIBFFI_CFLAGS) $(GLIB_HIDDEN_VISIBILITY_CFLAGS)
 
 libgobject_2_0_la_LIBADD = $(libglib) $(LIBFFI_LIBS)
 
-libgobject_2_0_la_DEPENDENCIES = $(gobject_win32_res) gobject.def
+libgobject_2_0_la_DEPENDENCIES = $(gobject_win32_res) $(gobject_def)
 
 #
 # setup source file variables

gthread/Makefile.am

@@ -28,6 +28,8 @@ top_builddir_full=`cd \$(top_builddir); pwd`
 lib_LTLIBRARIES = libgthread-2.0.la
 
 if OS_WIN32_AND_DLL_COMPILATION
+gthread_def = gthread.def
+export_symbols = -export-symbols $(gthread_def)
 if MS_LIB_AVAILABLE
 noinst_DATA = gthread-2.0.lib
 
@@ -62,15 +64,16 @@ gthread_win32_res = gthread-win32-res.o
 gthread_win32_res_ldflag = -Wl,$(gthread_win32_res)
 endif
 
+libgthread_2_0_la_CFLAGS = $(AM_CFLAGS) $(GLIB_HIDDEN_VISIBILITY_CFLAGS)
 libgthread_2_0_la_SOURCES = gthread-impl.c
 libgthread_2_0_la_LDFLAGS = $(GLIB_LINK_FLAGS) \
 	$(gthread_win32_res_ldflag) \
 	-version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE) \
-	-export-dynamic $(no_undefined) -export-symbols gthread.def
+	-export-dynamic $(no_undefined) $(export_symbols)
 
 libgthread_2_0_la_LIBADD = $(G_THREAD_LIBS_EXTRA) $(G_THREAD_LIBS_FOR_GTHREAD) $(libglib)
 
-libgthread_2_0_la_DEPENDENCIES = $(gthread_win32_res) gthread.def
+libgthread_2_0_la_DEPENDENCIES = $(gthread_win32_res) $(gthread_def)
 
 gthread-win32-res.o: gthread.rc
 	$(AM_V_GEN) $(WINDRES) gthread.rc $@