Date: Mon, 5 Sep 2022 09:07:49 -0600 From: Alan Somers <asomers@freebsd.org> To: Mark Johnston <markj@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, FreeBSD CURRENT <freebsd-current@freebsd.org> Subject: Re: Header symbols that shouldn't be visible to ports? Message-ID: <CAOtMX2g4VTkDDo2brr_371NnwZ80AFGmOvJy8XekVJy514YhJw@mail.gmail.com> In-Reply-To: <YxYNbLFSS%2B6yofig@nuc> References: <CAOtMX2h_=6AXYDSZNF77qQH9fF1gsJKuDP%2BM3dD%2Bq6Xw97bHmg@mail.gmail.com> <YxQzIf/xmwqz1Sn1@kib.kiev.ua> <CAOtMX2g0TkQvM6N0yf_fr667XpAFupyY6auf8_8H6VJt7MqEkA@mail.gmail.com> <YxYNbLFSS%2B6yofig@nuc>
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On Mon, Sep 5, 2022 at 8:53 AM Mark Johnston <markj@freebsd.org> wrote: > > On Mon, Sep 05, 2022 at 08:41:58AM -0600, Alan Somers wrote: > > On Sat, Sep 3, 2022 at 11:10 PM Konstantin Belousov <kostikbel@gmail.com> wrote: > > > > > > On Sat, Sep 03, 2022 at 10:19:12AM -0600, Alan Somers wrote: > > > > Our /usr/include headers define a lot of symbols that are used by > > > > critical utilities in the base system like ps and ifconfig, but aren't > > > > stable across major releases. Since they aren't stable, utilities > > > > built for older releases won't run correctly on newer ones. Would it > > > > make sense to guard these symbols so they can't be used by programs in > > > > the ports tree? There is some precedent for that, for example > > > > _WANT_SOCKET and _WANT_MNTOPTNAMES. > > > _WANT_SOCKET is clearly about exposing parts of the kernel definitions > > > for userspace code that wants to dig into kernel structures. Similarly > > > for _WANT_MNTOPTNAMES, but in fact this thing is quite stable. The > > > definitions are guarded by additional defines not due to their instability, > > > but because using them in userspace requires (much) more preparation from > > > userspace environment, which is either not trivial (_WANT_SOCKET) or > > > contradicts to standartized use of the header (_WANT_MNTOPTNAMES + > > > sys/mount.h). > > > > > > > > > > > I'm particular, I'm thinking about symbols like the following: > > > > MINCORE_SUPER > > > Why this symbol should be hidden? It is implementation-defined and > > > intended to be exposed to userspace. All MINCORE_* not only MINCORE_SUPER > > > are under BSD_VISIBLE braces, because POSIX does not define the symbols. > > > > Because it isn't stable. It changed for example in rev 847ab36bf22 > > for 13.0. Programs using the older value (including virtually every > > Rust program) won't work on 13.0 and later. > > Why won't they work? Code that tests (vec[i] & MINCORE_SUPER) using the > old value will still give the same result when running on a newer > kernel, since MINCORE_PSIND(1) is 0x20, the old MINCORE_SUPER value. > This isn't to say that the change was perfectly backwards compatible, > but I haven't seen an example of code which was broken by the change. Well, from mincore(2): In particular, applications compiled using the old value of MINCORE_SUPER will not identify large pages with size index 2 as being large pages.
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