Date: Sat, 26 Jun 2021 15:36:54 +0200 From: Dimitry Andric <dim@FreeBSD.org> To: Mark Millard <marklmi@yahoo.com> Cc: dev-commits-src-branches@freebsd.org Subject: Re: git: 450f3e55bdad - stable/13 - Work around bogus old gcc "initializer element is not constant" error Message-ID: <62DD1D7C-68FA-4931-A219-2C90A97A56A7@FreeBSD.org> In-Reply-To: <87104032-C5B9-447D-9545-B30AF983ACB7@yahoo.com> References: <87104032-C5B9-447D-9545-B30AF983ACB7.ref@yahoo.com> <87104032-C5B9-447D-9545-B30AF983ACB7@yahoo.com>
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[-- Attachment #1 --] On 26 Jun 2021, at 06:11, Mark Millard <marklmi@yahoo.com> wrote: > > Dimitry Andric dim at FreeBSD.org wrote on > Fri Jun 25 18:46:00 UTC 2021 : > > . . . >> In file included from /workspace/src/lib/msun/src/s_llround.c:11:0: >> /workspace/src/lib/msun/src/s_lround.c:54:31: error: initializer element is not constant >> static const type dtype_min = type_min - 0.5; >> ^~~~~~~~ >> /workspace/src/lib/msun/src/s_lround.c:55:31: error: initializer element is not constant >> static const type dtype_max = type_max + 0.5; >> ^~~~~~~~ >> >> Since 'type_min' and 'type_max' are constants declared just above these >> lines this error is nonsensical, but older gcc's are not smart enough. > . . . > > Well, in C "const" historically means closer to "read-only" than > to is-a-constant-expression in the language, unfortunately. Part > of this is the conversion away from being an lvalue (so: where > an lvalue is not required) loses the const qualification as part > of the conversion. FWIW, this changed in gcc 8.1+, here: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=f9c59f7e9511856bd6dc13d2d4904ebd9249c095 referencing these bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66618 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69960 In one of the comments, joseph@codesourcery.com mentions: > Although diagnosing this probably makes sense, it's not required by the > standard ("An implementation may accept other forms of constant > expressions." - and this expression doesn't contain "assignment, > increment, decrement, function-call, or comma operators", so isn't > required by the Constraints for constant expressions not to be one). I guess the gcc people also decided that POLA applied here. :) -Dimitry [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.2 iF0EARECAB0WIQR6tGLSzjX8bUI5T82wXqMKLiCWowUCYNctdgAKCRCwXqMKLiCW oyaBAKCIxLTfSv2mK433xEngt8cL7h8RwACfXQSraD/vRSxylfCnPel9wcMtvPw= =7uA2 -----END PGP SIGNATURE-----help
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