From: Fangrui Song Date: Mon, 29 Mar 2021 06:35:06 +0000 (-0700) Subject: sd-bus: set retain attribute on BUS_ERROR_MAP_ELF_REGISTER X-Git-Tag: v248-2~9 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=945317a4b69d33752c9513bb8994fe8d5a786ea6;p=thirdparty%2Fsystemd.git sd-bus: set retain attribute on BUS_ERROR_MAP_ELF_REGISTER LLD 13 and GNU ld 2.37 support -z start-stop-gc which allows garbage collection of C identifier name sections despite the __start_/__stop_ references. Simply set the retain attribute so that GCC 11 (if configure-time binutils is 2.36 or newer)/Clang 13 will set the SHF_GNU_RETAIN section attribute to prevent garbage collection. Without the patch, there are linker errors like the following with -z start-stop-gc. ``` ld: error: undefined symbol: __start_SYSTEMD_BUS_ERROR_MAP >>> referenced by bus-error.c:93 (../src/libsystemd/sd-bus/bus-error.c:93) >>> sd-bus_bus-error.c.o:(bus_error_name_to_errno) in archive src/libsystemd/libsystemd_static.a ``` --- diff --git a/src/libsystemd/sd-bus/bus-error.h b/src/libsystemd/sd-bus/bus-error.h index 557284faf82..d981f72449e 100644 --- a/src/libsystemd/sd-bus/bus-error.h +++ b/src/libsystemd/sd-bus/bus-error.h @@ -28,11 +28,17 @@ int bus_error_set_errnofv(sd_bus_error *e, int error, const char *format, va_lis * 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. + * + * In addition, set the retain attribute so that the section cannot be + * discarded by ld --gc-sections -z start-stop-gc. Older compilers would + * warn for the unknown attribute, so just disable -Wattributes. */ #define BUS_ERROR_MAP_ELF_REGISTER \ + _Pragma("GCC diagnostic ignored \"-Wattributes\"") \ _section_("SYSTEMD_BUS_ERROR_MAP") \ _used_ \ + __attribute__((retain)) \ _alignptr_ \ _variable_no_sanitize_address_