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. GNU ld before 2015-10 had the behavior as well. 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 with -z start-stop-gc (LLD default): ``` ld.lld: error: undefined symbol: __start___ell_debug ``` --- ell/log.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/ell/log.h b/ell/log.h index 924523b..32d6b8a 100644 --- a/ell/log.h +++ b/ell/log.h @@ -61,12 +61,18 @@ struct l_debug_desc { unsigned int flags; } __attribute__((aligned(8))); +// 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 L_DEBUG_SYMBOL(symbol, format, ...) do { \ +_Pragma("GCC diagnostic push") \ +_Pragma("GCC diagnostic ignored \"-Wattributes\"") \ static struct l_debug_desc symbol \ - __attribute__((used, section("__ell_debug"), aligned(8))) = { \ + __attribute__((used, retain, section("__ell_debug"), aligned(8))) = { \ .file = __FILE__, .func = __func__, \ .flags = L_DEBUG_FLAG_DEFAULT, \ }; \ +_Pragma("GCC diagnostic pop") \ if (symbol.flags & L_DEBUG_FLAG_PRINT) \ l_log(L_LOG_DEBUG, "%s:%s() " format, __FILE__, \ __func__ , ##__VA_ARGS__); \ -- 2.34