Re: HEADS-UP: Library version number bumps

On Wed, Sep 29, 2004 at 09:52:17AM -0400, Thomas Dickey wrote:
> On Wed, Sep 29, 2004 at 08:31:00AM -0400, Ken Smith wrote:
> > On Wed, Sep 29, 2004 at 07:27:10PM +1000, Tim Robbins wrote:
> > > On Tue, Sep 28, 2004 at 11:05:46PM -0400, Ken Smith wrote:
> > > > 
> > > > >From the "Better late than never" Department...
> > > > 
> > > > It looks like we should probably bump the version of a couple of
> > > > the system libraries.  With LOTS of help from Kris it looks like
> > > > this is the list we think needs a version bump, with the version
> > > > from 4.X being placed in compat4x:
> > > > 
> > > >        libgnuregex.so.2
> > > >        libhistory.so.4
> > > >        libm.so.2
> > > >        libncurses.so.5
> ....hmmm
> > > Why do they need to be bumped? Why use the version from 4.x? It sounds like
> > > this will break a lot of 5.x binaries.
> > > 
> > 
> > They need to be bumped because the internal workings of the libraries
> 
> that doesn't answer the question (libncurses hasn't changed its interface for
> some time - unless you're stating that the dynamic linker's changed
> incompatibly in some fashion).

libncurses.so.5 in 5.x does not export many of the global variables
exported by 4.x version of libncurses.so.5.  The missing symbols are:

    23: 0003e270     4 OBJECT  GLOBAL DEFAULT   12 SP
   166: 0000ee58    26 FUNC    GLOBAL DEFAULT    9 _nc_tracebits
   170: 00037c0e     2 OBJECT  GLOBAL DEFAULT   12 ospeed
   175: 00037c2c     4 OBJECT  GLOBAL DEFAULT   12 TABSIZE
   188: 00036870     4 OBJECT  GLOBAL DEFAULT   12 BC
   247: 00037744     4 OBJECT  GLOBAL DEFAULT   12 COLOR_PAIRS
   333: 00037c0c     1 OBJECT  GLOBAL DEFAULT   12 PC
   370: 00037c1c     4 OBJECT  GLOBAL DEFAULT   12 cur_term
   406: 00037540   512 OBJECT  GLOBAL DEFAULT   12 acs_map
   434: 00037748     4 OBJECT  GLOBAL DEFAULT   12 COLORS
   450: 0003e260     4 OBJECT  GLOBAL DEFAULT   12 stdscr
   495: 00037c28     4 OBJECT  GLOBAL DEFAULT   12 COLS
   498: 0003e268     4 OBJECT  GLOBAL DEFAULT   12 newscr
   515: 0003e264     4 OBJECT  GLOBAL DEFAULT   12 curscr
   528: 0003686c     4 OBJECT  GLOBAL DEFAULT   12 UP
   545: 00037c24     4 OBJECT  GLOBAL DEFAULT   12 LINES

A 4.x binary that calls _nc_tracebits() will fail outright when run on
5.x, but this is a debugging function and not likely to be widely used
in the real world, so that isn't a big deal.

However, if a 4.x binary sets one of the other variables in the above
list expecting it to have some effect on the library (or vice versa,
i.e. expects to read the state of the library by accessing the
globals), it will not behave the same way when run on 5.x.

If I'm mistaken about the implications (perhaps you can guarantee that
the above will not happen), please let us know.

Kris