Define JNIEXPORT as visibility default with GCC?

[David Holmes]

On 15/02/2013 5:26 PM, Jeremy Manson wrote:
> a) I don't know what's going on behind the scenes, but if this sounds
> like a good idea to folks, can we open a bug and get the process
> otherwise rolling?
>
> b) Martin, where did the 4.2 restriction come from?  Both Apple's site
> and the gcc wiki say that visibility support arrived in 4.0:

 From the original push for 6588413 in linux gcc.make:

+# version 4 and above support fvisibility=hidden (matches jni_x86.h file)
+# except 4.1.2 gives pointless warnings that can't be disabled (afaik)

So it was limited on x86 to >2 (which I think was a typo: intended to be 
 >=2 or >1 ?)

Of course the bsd port copied the linux file.

David

> http://gcc.gnu.org/wiki/Visibility
> https://developer.apple.com/library/mac/#documentation/DeveloperTools/Conceptual/CppRuntimeEnv/Articles/SymbolVisibility.html
>
>
> On Thu, Feb 14, 2013 at 3:01 PM, David DeHaven <david.dehaven at oracle.com
> <mailto:david.dehaven at oracle.com>> wrote:
>
>
>      >>>> +#if defined(__GNUC__) && (__GNUC__ > 4) || (__GNUC__ == 4) &&
>      >>>> (__GNUC_MINOR__ > 2)
>      >>>> +  #define JNIEXPORT     __attribute__((visibility("default")))
>      >>>> +  #define JNIIMPORT     __attribute__((visibility("default")))
>      >>>
>      >>> The default compiler in Xcode 4.1 is llvm-gcc 4.2, it seems.
>       The conditional above excludes that.  Is this intentional?
>      >>
>      >> It's *is* gcc, with a LLVM backend.
>      >
>      > Yes, but it identifies itself as GCC 4.2, so the conditional
>     doesn't fire.
>
>     I assume this was not the intent and the version check is just wrong.
>
>
> It may be that they deliberately stayed with gcc 4.2 to keep parity with
> clang, which only supports 4.2 (or it may not, because clang supports
> lots of 4.3+ features).
>
>
>
>      > If Xcode is fine with the #define, I suggest to drop the version
>     check completely.  We already do not support compiling with GCC
>     versions which are so old that they lack visibility support.
>
>
>     If it were Mac only, I'd agree.
>
>     The same header is currently used for all "unix-like" OS's (which
>     may change, if I have my way), so Solaris and Linux would also be
>     affected. Most Linux distros have used gcc 4 for quite a while now,
>     I've no idea what Solaris uses and embedded targets are a wild
>     mishmash of whatever someone manages to cobble together, so the
>     simpler __GNUC__ check may still be appropriate.
>
>     -DrD-
>
>