Date: Mon, 22 Jan 2018 20:05:23 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Kyle Evans <kevans@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r328240 - in head: etc/mtree lib lib/libc/regex lib/libc/tests/regex lib/libregex lib/libregex/tests share/mk Message-ID: <20180122180523.GH55707@kib.kiev.ua> In-Reply-To: <CACNAnaGwTkhKqCsb420VnOW7vRmbURWtoV7rPwmK88f2-AQGnA@mail.gmail.com> References: <201801220244.w0M2if3I083081@repo.freebsd.org> <20180122102639.GD55707@kib.kiev.ua> <CACNAnaEWrWxruMgVKUyoE-sUqHv29ONhitHO6y25QnT3XD9AUA@mail.gmail.com> <20180122155307.GG55707@kib.kiev.ua> <CACNAnaGwTkhKqCsb420VnOW7vRmbURWtoV7rPwmK88f2-AQGnA@mail.gmail.com>
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On Mon, Jan 22, 2018 at 11:43:34AM -0600, Kyle Evans wrote: > On Mon, Jan 22, 2018 at 9:53 AM, Konstantin Belousov > <kostikbel@gmail.com> wrote: > > On Mon, Jan 22, 2018 at 08:05:30AM -0600, Kyle Evans wrote: > >> On Mon, Jan 22, 2018 at 4:26 AM, Konstantin Belousov > >> <kostikbel@gmail.com> wrote: > >> > On Mon, Jan 22, 2018 at 02:44:41AM +0000, Kyle Evans wrote: > >> >> Author: kevans > >> >> Date: Mon Jan 22 02:44:41 2018 > >> >> New Revision: 328240 > >> >> URL: https://svnweb.freebsd.org/changeset/base/328240 > >> >> > >> >> Log: > >> >> Add libregex, connect it to the build > >> >> > >> >> libregex is a regex(3) implementation intended to feature GNU extensions and > >> >> any other non-POSIX compliant extensions that are deemed worthy. > >> >> > >> >> These extensions are separated out into a separate library for the sake of > >> >> not cluttering up libc further with them as well as not deteriorating the > >> >> speed (or lack thereof) of the libc implementation. > >> >> > >> >> libregex is implemented as a build of the libc implementation with LIBREGEX > >> >> defined to distinguish this from a libc build. The reasons for > >> >> implementation like this are two-fold: > >> >> > >> >> 1.) Maintenance- This reduces the overhead induced by adding yet another > >> >> regex implementation to base. > >> >> > >> >> 2.) Ease of use- Flipping on GNU extensions will be as simple as linking > >> >> against libregex, and POSIX-compliant compilations can be guaranteed with a > >> >> REG_POSIX cflag that should be ignored by libc/regex and disables extensions > >> >> in libregex. It is also easier to keep REG_POSIX sane and POSIX pure when > >> >> implemented in this fashion. > >> > You are doing very fragile and unmaintainable trick on all consumers > >> > there. Your libregex.so exports the same symbols under the same version > >> > as the libc does. In other words, we now provide two binary-incompatible > >> > callable symbols, and selection of the symbol by the consumer depends on > >> > the DT_NEEDED order and interposing. For instance, if some program loads > >> > a module linked to your libregex, the program behaviour suddenly changes. > >> > > >> > Since the library provides incompatible implementation, it must use > >> > different versions for the symbols, at least to save others time to > >> > debug the mess. > >> > >> What's the best way that you see, going forward? > >> > >> I'm inclined to throw a Symbol.map into libregex using FBSD_1.1... > >> these interfaces are otherwise stable stable within the two respective > >> libraries, so I don't see that causing too much pain in the future > >> because symbol version changes should be rare. > > I do not think this is wise to create contention on the standard FreeBSD' > > version namespace. > > > >> > >> On the other hand, I could see wanting to use something more like > >> FBSD_LIBREGEX_1.0 so that if the situation does come up one doesn't > >> need to double-check that they're not colliding with the other > >> implementation. > > I like this more. We still have to carry that symbols with the current > > behaviour forever, but at least they would no longer conflict with the > > libc' symbols for dynamic linking. > > Right- that makes sense. Would you object to the following patch? The > versioning was botched in the first place because of no VERSION_DEF. > I've also dropped the FBSD_ prefix from my previous mention of it > because there seems to be no good justification or precedent for it > elsewhere in the tree that I've found. This looks fine. I would suggest to add the explanation why a different version name was used there, in particular, to highlight that the symbols otherwise conflict with the symbols from libc. > > diff --git a/lib/libregex/Makefile b/lib/libregex/Makefile > index eb6b0b64650..8ac496dd9f7 100644 > --- a/lib/libregex/Makefile > +++ b/lib/libregex/Makefile > @@ -9,7 +9,8 @@ SHLIB_MINOR= 0 > > CFLAGS+= -DLIBREGEX > LIBC_SRCTOP= ${.CURDIR:H}/libc > -SYMBOL_MAPS= ${SYM_MAPS} > +VERSION_DEF= ${.CURDIR}/Versions.def > +SYMBOL_MAPS= ${.CURDIR}/Symbol.map > WARNS?= 2 > > #HAS_TESTS= > diff --git a/lib/libregex/Symbol.map b/lib/libregex/Symbol.map > new file mode 100644 > index 00000000000..1b77bd85aca > --- /dev/null > +++ b/lib/libregex/Symbol.map > @@ -0,0 +1,10 @@ > +/* > + * $FreeBSD$ > + */ > + > +LIBREGEX_1.0 { > + regcomp; > + regerror; > + regexec; > + regfree; > +}; > diff --git a/lib/libregex/Versions.def b/lib/libregex/Versions.def > new file mode 100644 > index 00000000000..b6c84200762 > --- /dev/null > +++ b/lib/libregex/Versions.def > @@ -0,0 +1,5 @@ > +# $FreeBSD$ > + > +LIBREGEX_1.0 { > +}; > +
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