objective-ccocoa-touchllvmllvm-4.0

Warning "Use of GNU statement expression extension"

I have this Objective-C istruction:

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

where a and bare NSUIntegers.

MIN() is the macro defined in the standard NSObjCRuntime.hheader file as:

#if !defined(MIN)
   #define MIN(A,B) ({ __typeof__(A) __a = (A); __typeof__(B) __b = (B); __a < __b ? __a : __b; })
#endif

During the compilation, the LLVM Compiler 4.1 highlights my instruction showing the warning: "Use of GNU statement expression extension".

What does this mean? Is it my fault? If yes, how can I fix it? If not, how can I remove the compiler warning?

Solution

  • 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.)