I've been refactoring my horrible mess of C++ type-safe psuedo-enums to the new C++0x type-safe enums because they're way more readable. Anyway, I use them in exported classes, so I explicitly mark them to be exported:
enum class  __attribute__((visibility("default"))) MyEnum : unsigned int
{
    One = 1,
    Two = 2
};
Compiling this with g++ yields the following warning:
type attributes ignored after type is already defined
This seems very strange, since, as far as I know, that warning is meant to prevent actual mistakes like:
class __attribute__((visibility("default"))) MyClass { };
class __attribute__((visib开发者_如何学JAVAility("hidden")))  MyClass;
Of course, I'm clearly not doing that, since I have only marked the visibility attributes at the definition of the enum class and I'm not re-defining or declaring it anywhere else (I can duplicate this error with a single file).
Ultimately, I can't make this bit of code actually cause a problem, save for the fact that, if I change a value and re-compile the consumer without re-compiling the shared library, the consumer passes the new values and the shared library has no idea what to do with them (although I wouldn't expect that to work in the first place).
Am I being way too pedantic?  Can this be safely ignored?  I suspect so, but at the same time, having this error prevents me from compiling with Werror, which makes me uncomfortable.  I would really like to see this problem go away.
You can pass the -Wno-attributes flag to turn the warning off.
(It's probably a bug in gcc?)
It works for me with g++ 4.8.2 the following way:
enum class MyEnum : unsigned int
__attribute__((visibility("default")))
{
    One = 1,
    Two = 2
};
(change the position of the attribute declaration)
 
         
                                         
                                         
                                         
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