build-sys: hide magic section variables from exported symbols

https://github.com/systemd/systemd/issues/234

Makefile.am

@@ -3460,10 +3460,6 @@ libudev_la_SOURCES =\
 	src/libudev/libudev-queue.c \
 	src/libudev/libudev-hwdb.c
 
-libudev_la_CFLAGS = \
-	$(AM_CFLAGS) \
-	-fvisibility=hidden
-
 libudev_la_LDFLAGS = \
 	$(AM_LDFLAGS) \
 	-version-info $(LIBUDEV_CURRENT):$(LIBUDEV_REVISION):$(LIBUDEV_AGE) \
@@ -3495,10 +3491,6 @@ noinst_LTLIBRARIES += \
 libudev_internal_la_SOURCES =\
 	$(libudev_la_SOURCES)
 
-libudev_internal_la_CFLAGS = \
-	$(AM_CFLAGS) \
-	-fvisibility=default
-
 # ------------------------------------------------------------------------------
 INSTALL_DIRS += \
 	$(sysconfdir)/udev/rules.d
@@ -5539,8 +5531,7 @@ pam_systemd_la_SOURCES = \
 
 pam_systemd_la_CFLAGS = \
 	$(AM_CFLAGS) \
-	$(PAM_CFLAGS) \
-	-fvisibility=hidden
+	$(PAM_CFLAGS)
 
 pam_systemd_la_LDFLAGS = \
 	$(AM_LDFLAGS) \

src/libsystemd/sd-bus/bus-error.c

@@ -70,9 +70,11 @@ BUS_ERROR_MAP_ELF_REGISTER const sd_bus_error_map bus_standard_errors[] = {
         SD_BUS_ERROR_MAP_END
 };
 
-/* GCC maps this magically to the beginning and end of the BUS_ERROR_MAP section */
-extern const sd_bus_error_map __start_BUS_ERROR_MAP[];
-extern const sd_bus_error_map __stop_BUS_ERROR_MAP[];
+/* GCC maps this magically to the beginning and end of the BUS_ERROR_MAP section.
+ * Hide them; for currently unknown reasons they get exported to the shared libries
+ * even without being listed in the sym file. */
+extern const sd_bus_error_map __start_BUS_ERROR_MAP[] _hidden_;
+extern const sd_bus_error_map __stop_BUS_ERROR_MAP[] _hidden_;
 
 /* Additional maps registered with sd_bus_error_add_map() are in this
  * NULL terminated array */