diff mbox series

[RFC,2/2] batctl: Fix build with lld-13 or ld 2.37 start-stop-gc

Message ID 20210605124549.94021-1-sven@narfation.org
State New
Delegated to: Simon Wunderlich
Headers show
Series [RFC,1/2] batctl: Combine command section attributes | expand

Commit Message

Sven Eckelmann June 5, 2021, 12:45 p.m. UTC 
If ld 2.37 with -Wl,-z,start-stop-gc -Wl,--gc-sections or lld-13 with
-Wl,--gc-sections, the build with either fail with

  ld.lld: error: undefined symbol: __start___command
  >>> referenced by main.c
  >>>               main.o:(main)
  >>> referenced by main.c
  >>>               main.o:(main)
  >>> referenced by main.c
  >>>               main.o:(print_usage)
  >>> referenced 1 more time

Or in case of ld 2.37 just show a single command (aggregation). A new
attribute retain was introduced which is then emitting the ELF flag
SHF_GNU_RETAIN. This will cause the garbage collector to retain this
section.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 main.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
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Patch

diff --git a/main.h b/main.h
index 00b2ab3..6b11acc 100644
--- a/main.h
+++ b/main.h
@@ -101,6 +101,12 @@  struct command {
 	const char *usage;
 };
 
+#if defined(__has_attribute) && __has_attribute(retain)
+#define start_stop_retain __attribute__((retain))
+#else
+#define start_stop_retain
+#endif
+
 #define COMMAND_NAMED(_type, _name, _abbr, _handler, _flags, _arg, _usage) \
 	static const struct command command_ ## _name ## _ ## _type = { \
 		.type = (_type), \
@@ -112,7 +118,7 @@  struct command {
 		.usage = (_usage), \
 	}; \
 	static const struct command *__command_ ## _name ## _ ## _type \
-	__attribute__((__used__,__section__ ("__command"))) = &command_ ## _name ## _ ## _type
+	__attribute__((__used__,__section__ ("__command"))) start_stop_retain = &command_ ## _name ## _ ## _type
 
 #define COMMAND(_type, _handler, _abbr, _flags, _arg, _usage) \
 	COMMAND_NAMED(_type, _handler, _abbr, _handler, _flags, _arg, _usage)