sd-bus: rework ELF error mapping table magic

The ELF magic cannot work for consumers of our shard library, since they
are in a different module. Hence make all the ELF magic private, and
instead introduce a public function to register additional static
mapping table.

1 files changed, 31 insertions, 6 deletions

diff --git a/src/libsystemd/sd-bus/bus-error.h b/src/libsystemd/sd-bus/bus-error.h
index 1469486187..56297156a9 100644
--- a/src/libsystemd/sd-bus/bus-error.h
+++ b/src/libsystemd/sd-bus/bus-error.h
@@ -26,15 +26,40 @@
 #include "sd-bus.h"
 #include "macro.h"
 
-struct name_error_mapping {
-        const char* name;
-        int code;
-};
-typedef struct name_error_mapping name_error_mapping;
-
 bool bus_error_is_dirty(sd_bus_error *e);
 
 const char *bus_error_message(const sd_bus_error *e, int error);
 
 int bus_error_setfv(sd_bus_error *e, const char *name, const char *format, va_list ap) _printf_(3,0);
 int bus_error_set_errnofv(sd_bus_error *e, int error, const char *format, va_list ap) _printf_(3,0);
+
+#define BUS_ERROR_OOM SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_NO_MEMORY, "Out of memory")
+#define BUS_ERROR_FAILED SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_FAILED, "Operation failed")
+
+/*
+ * There are two ways to register error maps with the error translation
+ * logic: by using BUS_ERROR_MAP_ELF_REGISTER, which however only
+ * works when linked into the same ELF module, or via
+ * sd_bus_error_add_map() which is the official, external API, that
+ * works from any module.
+ *
+ * Note that BUS_ERROR_MAP_ELF_REGISTER has to be used as decorator in
+ * the bus error table, and BUS_ERROR_MAP_ELF_USE has to be used at
+ * least once per compilation unit (i.e. per library), to ensure that
+ * the error map is really added to the final binary.
+ */
+
+#define BUS_ERROR_MAP_ELF_REGISTER                                      \
+        __attribute__ ((__section__("BUS_ERROR_MAP")))                  \
+        __attribute__ ((__used__))                                      \
+        __attribute__ ((aligned(8)))
+
+#define BUS_ERROR_MAP_ELF_USE(errors)                                   \
+        extern const sd_bus_error_map errors[];                         \
+        __attribute__ ((used)) static const sd_bus_error_map * CONCATENATE(errors ## _copy_, __COUNTER__) = errors;
+
+/* We use something exotic as end marker, to ensure people build the
+ * maps using the macsd-ros. */
+#define BUS_ERROR_MAP_END_MARKER -'x'
+
+BUS_ERROR_MAP_ELF_USE(standard_errors);