Date: Thu, 27 Feb 2020 16:37:49 -0800 From: John Baldwin <jhb@FreeBSD.org> To: Mark Millard <marklmi@yahoo.com>, svn-src-head@freebsd.org Cc: Warner Losh <imp@bsdimp.com> Subject: Re: svn commit: r358392 - head/share/man/man9 Message-ID: <59374055-922a-81f1-1b05-a572e1cb6b1a@FreeBSD.org> In-Reply-To: <217D39BA-4FDC-490C-8490-533D244E79CE@yahoo.com> References: <217D39BA-4FDC-490C-8490-533D244E79CE.ref@yahoo.com> <217D39BA-4FDC-490C-8490-533D244E79CE@yahoo.com>
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On 2/27/20 2:45 PM, Mark Millard wrote: > John Baldwin jhb at FreeBSD.org wrote on > Thu Feb 27 16:55:01 UTC 2020: > >> On 2/27/20 7:30 AM, Warner Losh wrote: >>> Author: imp >>> Date: Thu Feb 27 15:30:13 2020 >>> New Revision: 358392 >>> URL: https://svnweb.freebsd.org/changeset/base/358392 >>> >>> Log: >>> _Static_assert is to be preferred to CTASSERT. >>> >>> Document the existing prefernce that _Static_assert be used in preference to the >>> old CTASSERT we used to use for compile time assertions. >> >> Actually, I think what we want to use is static_assert(). The intention in >> userland C is that _Static_assert() is an internal keyword and <assert.h> >> adds static_assert() as an alias, similar to <stdalign.h> defining alignas, >> etc. I think what we should do for the kernel is have <sys/systm.h> define >> map static_assert to _Static_assert and replace existing _Static_assert >> usage with the proper spelling. >> > > Be warned static_assert is a C++ keyword as of C++11. > > c++11 added: static_assert(bool_constexpr,message) > c++17 added: static_assert(bool_constexpr) > > C11 added _Static_assert(expression,message) > C2x gets _Static_assert(expression) > > C11 added "#define static_assert _Static_assert" to <assert.h> > > It makes for a bit of a mess in code to be allowed > to be processed by both C and C++. > > The wording may need to specify enough to tell what to > do for such code and the headers may need logic to > cause that context to exist across both languages > when the header is allowed for both. The intent of the C11 changes is to permit equivalent use of static_assert() in both languages. The #define in <assert.h> is guarded to not kick in for C++. -- John Baldwin
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