[PATCH] socket: Use offsetof in SUN_LEN (bug 29578)

[Andreas Schwab]

Use offsetof instead of its traditional expansion in the definition of the
SUN_LEN macro, to avoid a warning from the undefined behaviour sanitizer.
---
 socket/sys/un.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/socket/sys/un.h b/socket/sys/un.h
index 454eafebc9..2b11300e28 100644
--- a/socket/sys/un.h
+++ b/socket/sys/un.h
@@ -34,10 +34,11 @@ struct sockaddr_un
 
 
 #ifdef __USE_MISC
+# include <stddef.h>
 # include <string.h>		/* For prototype of `strlen'.  */
 
 /* Evaluate to actual length of the `sockaddr_un' structure.  */
-# define SUN_LEN(ptr) ((size_t) (((struct sockaddr_un *) 0)->sun_path)	      \
+# define SUN_LEN(ptr) (offsetof (struct sockaddr_un, sun_path)		      \
 		      + strlen ((ptr)->sun_path))
 #endif
 
-- 
2.37.3


-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
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