container_of: work with -Wcast-qual

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/ccan/container_of/container_of.h b/ccan/container_of/container_of.h
index 2943b8f098d5e3eba3d7f71a439712dde01df04d..0449935056f51a84af2a84f5b2dd7fcbf48c7678 100644 (file)
--- a/ccan/container_of/container_of.h
+++ b/ccan/container_of/container_of.h
@@ -103,7 +103,7 @@
        container_off(typeof(*var), member)
 #else
 #define container_off_var(var, member)                 \
-       ((char *)&(var)->member - (char *)(var))
+       ((const char *)&(var)->member - (const char *)(var))
 #endif
 
 #endif /* CCAN_CONTAINER_OF_H */