[prev in list] [next in list] [prev in thread] [next in thread] 

List:       busybox
Subject:    re: [PATCH] Fix const pointer assignment trick on clang 9+
From:       David Laight <David.Laight () ACULAB ! COM>
Date:       2021-11-15 11:05:22
Message-ID: 409fc7ad81934748a790cb28755cb24a () AcuMS ! aculab ! com
[Download RAW message or body]

If you are trying to tell the compiler that a pointer
(or other value) might change and it mustn't reload it (etc)
then this might work:

#define LAUNDER(val_in, val_out) \
	asm volatile ( "" : "&r" (val_out) : "0" (val_in))

That is (more or less) equivalent to:
	val_out = (typeof(val_out))val_in;
except that the compiler can't track the value.
(assuming it doesn't 'peek inside' the asm.)

	David
 

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

_______________________________________________
busybox mailing list
busybox@busybox.net
http://lists.busybox.net/mailman/listinfo/busybox
[prev in list] [next in list] [prev in thread] [next in thread]