RFR: 8086027: Multiple STATIC_ASSERTs at class scope doesn't work (original) (raw)

Kim Barrett kim.barrett at oracle.com
Tue Jun 9 18:39:21 UTC 2015

On Jun 9, 2015, at 2:17 AM, David Holmes <david.holmes at oracle.com> wrote:

Hi Kim, On 9/06/2015 3:51 PM, Kim Barrett wrote: Third time's the charm?

Please review this change to the STATICASSERT macro, to allow multiple assertions in the same class scope. It seems we do need to make the typedef names used in the expansion unique per scope; see CR for details. We accomplish this with preprocessor token pasting with LINE (done correctly, unlike in the change for JDK-8067306). Seems okay to me (but then so did previous version ).

Thanks for reviewing. And yeah, sorry about that.

As part of this, I'm also adding PASTETOKENS(x, y) utility macro. I'm willing to entertain alternative naming suggestions, though hoping to avoid a bikeshed discussion. As we already have XSTR for the single token case, what about XSTRCAT ?

As there aren’t any strings involved, only pp tokens, I don’t care for a name related to strings.

Bengt’s suggestion of XCAT is a better match for the existing XSTR, but I dislike short global macro names as being too easy for collisions to occur. For an example of the problem, see the little dance around STR in os/solaris/vm/attachListener_solaris.cpp.

And I’m not sure what the X prefix is supposed to indicate. Maybe XCAT is supposed to be eXtended conCATenation? I prefer words.

I chose the current name based on a common name for ## being the “token pasting operator”. It’s also sometimes referred to as joining rather than pasting, though that seems less frequent. C++ standards just call it the “## operator”, though there’s an example in C++11 that defines a macro called “join” that uses it. And some commonly used libraries do use “cat”. (Boost has both BOOST_PP_CAT and BOOST_JOIN, which have different implementations because they use different approaches to detecting and working around preprocessor deficiencies.) But I wouldn’t want to use “JOIN” because that already has other meanings, such as with thread joining.

I guess that’s a long-winded way of saying I’m planning to stick with PASTE_TOKENS.

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