svn commit: r328240 - in head: etc/mtree lib lib/libc/regex lib/libc/tests/regex lib/libregex lib/libregex/tests share/mk

[Kyle Evans]

On Mon, Jan 22, 2018 at 9:53 AM, Konstantin Belousov
<kostikbel at 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 at 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.

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 {
+};
+