Warning “Use of GNU statement expression extension”

Question

I have this Objective-C istruction:

NSRange range = NSMakeRange(i, MIN(a, b));

where a and bare NSUInteger<

Answer 1

It’s a late answer, I know, but you can avoid this message by adding -Wno-gnu to your compiler flags.

(In Xcode 5 I believe you can change this by going to your project’s Build Settings and adding -Wno-gnu to the “Other C Flags”, which are in the “Apple LLVM 5.0 – Custom Compiler Flags” section.)

Answer 2

"Statement expressions" is an extension of the GNU C compiler and allows you to execute a group of statements, returning the value of the last statement:

x = ({
    statement1;
    statement2;
    statement3;
});

In the above example, x will have the value returned by statement3.

It is a convenient feature that enables you to have multi-statement macros that can be nested easily into other expressions. It is not, however, defined by any C standard.

Answer 3

Don't use -Wno-gnu, that shuts down too many warnings. Instead, use:

-Wno-gnu-statement-expression

Answer 4

Statement expressions have been declared.

You can selectively ignore the warning by using pragma codes without changing project settings.

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wgnu"

NSRange range = NSMakeRange(i, MIN(a, b));

#pragma GCC diagnostic pop