objective c - How can I get rid of an "unused variable" warning in Xcode?

Question

I understand exactly why unused variable warnings occur. I don't want to suppress them in general, because they are incredibly useful in most cases. However, consider the following (contrived) code.

NSError *error = nil;
BOOL saved = [moc save:&error];
NSAssert1(saved, @"Dude!!1! %@!!!", error);

Xcode reports that saved is an unused variable, when of course it isn't. I suspect this is because NSAssert1 is a macro. The NS_BLOCK_ASSERTIONS macro is not defined, so Objective C assertions are definitely enabled.

While it doesn't hurt anything, I find it untidy and annoying, and I want to suppress it, but I'm not sure how to do so. Assigning the variable to itself gets rid of the compiler warning, but I'd rather do it the "right" way if such a thing exists.

Answer 1

I'm unsure if it's still supported in the new LLVM compiler, but GCC has an "unused" attribute you can use to suppress that warning:

BOOL saved __attribute__((unused)) = [moc save:&error];

Alternatively (in case LLVM doesn't support the above), you could split the variable declaration into a separate line, guaranteeing that the variable would be "used" whether the macro expands or not:

BOOL saved = NO;
saved = [moc save:&error];