Re: Serious side effect when building ncurses with pcre2

[Ken Gaillot]

On Thu, 2021-03-25 at 14:47 -0400, Thomas Dickey wrote:
> On Thu, Mar 25, 2021 at 02:44:13PM -0400, Thomas Dickey wrote:
> > On Thu, Mar 25, 2021 at 11:18:04AM -0500, Ken Gaillot wrote:
> > > Hi all,
> > > 
> > > I help maintain a project that uses both ncurses and the standard
> > > C
> > > regex API. We stumbled into an issue during CI testing.
> > > 
> > > A distribution (OpenSUSE tumbleweed) built ncurses using the --
> > > with-
> > > pcre2 option. Since we link against the ncurses library, this
> > > brought
> > 
> > You're describing a problem with OpenSUSE's package,
> > rather than a bug in ncurses -- the proper place to
> > discuss this is in OpenSUSE's bugzilla:
> > 
> > https://bugzilla.opensuse.org
> 
> https://bugzilla.opensuse.org/show_bug.cgi?id=1183960

Yes, I mentioned the OpenSUSE bug in my message.

But it is not solely an OpenSUSE issue.

If libncurses is configured using --with-pcre, that will break any
ncurses-using application's use of the standard C regex API, when
libpcre2-posix isn't installed as the system regex.h (which it usually
isn't).

Someone rebuilding their ncurses library would have no indication that
this will be the case. Some ncurses-using applications would simply
stop working in a way that is extremely difficult to troubleshoot.
There would be no indication that ncurses was related to the errors,
and any error messages would be misleading (since the regex error codes
would themselves be part of the problem).

Upgrade ncurses -> regular expressions stop working in one or more
applications. That's a tough connection to make.

Even in a distribution, which is where this is most important, how is
the ncurses packager to know that a configuration choice could break
completely unrelated functionality in packages they may not even know
exist? And how long will it take the packager of a broken application
to figure out what happened, when the error will have nothing to do
with ncurses functionality?
-- 
Ken Gaillot <kgaillot@redhat.com>