On 07/23/2015 06:50 AM, Jeffrey Walton wrote:
Our project has a static assert. Its creating a noisy output at -Wall
and above. We attempted to manage it with a GCC diagnostic block, but
its not quite meeting expectations. The static assert creates a bunch
of unused variable warnings.
We have a UNUSED macro that casts to a void (its the only portable way
I know to clear an unused warning), but we don't have a variable name
to use with it.
How can we clear a warning like `unused variable 'assert_26'
[-Wunused-variable]|`?
One common way is by defining a type. In your case, it can be done
by changing CompileAssert to define a typedef like so:
template <bool b>
struct CompileAssert
{
typedef char dummy[2*b-1];
};
and COMPILE_ASSERT_INSTANCE to use the type:
#define COMPILE_ASSERT_INSTANCE(assertion, instance) \
typedef CompileAssert<(assertion)>::dummy \
ASSERT_JOIN(assert_, instance)
This will, however, emit a -Wunused-local-typedefs warning when
used in a local scope.
Using an enum instead can get around that:
template <bool> struct CompileAssert;
template <> struct CompileAssert<true> { };
#define COMPILE_ASSERT_INSTANCE(assertion, instance) \
enum { ASSERT_JOIN(assert_, instance) = \
sizeof (CompileAssert<(assertion)>) }
But perhaps the simplest and least intrusive approach, if you
can't use static_assert, is to annotate the unused variable with
attribute unused:
#define COMPILE_ASSERT_INSTANCE(assertion, instance) \
static CompileAssert<(assertion)> \
ASSERT_JOIN(assert_, instance) __attribute__ ((unused))
Martin
