From: Alejandro Colomar <alx@kernel.org>
Date: Sun, 18 Feb 2024 17:32:31 +0000 (+0100)
Subject: lib/sizeof.h: memberof(): Add macro
X-Git-Tag: 4.15.0-rc3~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=544709fad3b2dd05f22414c1b70be53e6a3504f1;p=thirdparty%2Fshadow.git

lib/sizeof.h: memberof(): Add macro

This macro is useful to get the size of a member of a structure
without having a variable of that type.

Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/lib/sizeof.h b/lib/sizeof.h
index f16e1a7bf..6847068ea 100644
--- a/lib/sizeof.h
+++ b/lib/sizeof.h
@@ -15,10 +15,11 @@
 #include "must_be.h"
 
 
-#define WIDTHOF(x)       (sizeof(x) * CHAR_BIT)
-#define SIZEOF_ARRAY(a)  (sizeof(a) + must_be_array(a))
-#define NITEMS(a)        (SIZEOF_ARRAY((a)) / sizeof((a)[0]))
-#define STRLEN(s)        (NITEMS(s) - 1)
+#define memberof(T, member)  ((T){}.member)
+#define WIDTHOF(x)           (sizeof(x) * CHAR_BIT)
+#define SIZEOF_ARRAY(a)      (sizeof(a) + must_be_array(a))
+#define NITEMS(a)            (SIZEOF_ARRAY((a)) / sizeof((a)[0]))
+#define STRLEN(s)            (NITEMS(s) - 1)
 
 
 #endif  // include guard