Re: Refactor compile-time assertion checks for C/C++

Michael Paquier <michael(at)paquier(dot)xyz> writes:
> Indeed the bot is happy now. By looking at the patch, one would note
> that what it just does is unifying the fallback "hack-ish"
> implementations so as C and C++ use the same thing, which is the
> fallback implementation for C of HEAD. I would prefer hear first from
> more people to see if they like this change. Or not.

I looked at this and tried it on an old (non HAVE__STATIC_ASSERT)
gcc version. Seems to work, but I have a couple cosmetic suggestions:

1. The comment block above this was never updated to mention that
we're now catering for C++ too. Maybe something like

* gcc 4.6 and up supports _Static_assert(), but there are bizarre syntactic
* placement restrictions. Macros StaticAssertStmt() and StaticAssertExpr()
* make it safe to use as a statement or in an expression, respectively.
* The macro StaticAssertDecl() is suitable for use at file scope (outside of
* any function).
*
+ * On recent C++ compilers, we can use standard static_assert().
+ *
* Otherwise we fall back on a kluge that assumes the compiler will complain
* about a negative width for a struct bit-field. This will not include a
* helpful error message, but it beats not getting an error at all.

2. I think you could simplify the #elif to just

#elif defined(__cplusplus) && __cpp_static_assert >= 200410

Per the C standard, an unrecognized identifier in an #if condition
is replaced by zero. So the condition will come out false as desired
if __cpp_static_assert isn't defined; you don't need to test that
separately.

regards, tom lane