I intend to make further use of this in upcoming commits. Signed-off-by: Ben Pfaff <b...@ovn.org> --- lib/util.h | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/lib/util.h b/lib/util.h index 0ad75f2..afd8e37 100644 --- a/lib/util.h +++ b/lib/util.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc. + * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 Nicira, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -79,6 +79,22 @@ #endif OVS_NO_RETURN void ovs_assert_failure(const char *, const char *, const char *); +/* This is a void expression that issues a compiler error if POINTER cannot be + * compared for equality with the given pointer TYPE. This generally means + * that POINTER is a qualified or unqualified TYPE. However, + * BUILD_ASSERT_TYPE(POINTER, void *) will accept any pointer to object type, + * because any pointer to object can be compared for equality with "void *". + * + * POINTER can be any expression. The use of "sizeof" ensures that the + * expression is not actually evaluated, so that any side effects of the + * expression do not occur. + * + * The cast to int is present only to suppress an "expression using sizeof + * bool" warning from "sparse" (see + * http://permalink.gmane.org/gmane.comp.parsers.sparse/2967). */ +#define BUILD_ASSERT_TYPE(POINTER, TYPE) \ + ((void) sizeof ((int) ((POINTER) == (TYPE) (POINTER)))) + /* Casts 'pointer' to 'type' and issues a compiler warning if the cast changes * anything other than an outermost "const" or "volatile" qualifier. * @@ -86,7 +102,7 @@ OVS_NO_RETURN void ovs_assert_failure(const char *, const char *, const char *); * bool" warning from "sparse" (see * http://permalink.gmane.org/gmane.comp.parsers.sparse/2967). */ #define CONST_CAST(TYPE, POINTER) \ - ((void) sizeof ((int) ((POINTER) == (TYPE) (POINTER))), \ + (BUILD_ASSERT_TYPE(POINTER, TYPE), \ (TYPE) (POINTER)) extern char *program_name; -- 2.1.3 _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
