From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bart Veer <bartv@redhat.com>
To: andrew.lunn@ascom.ch
Cc: jld@redhat.com, ecos-discuss@sourceware.cygnus.com
Subject: Re: [ECOS] serial_devio renamaed to cyg_serial_devio
Date: Wed, 14 Jun 2000 04:58:00 -0000
Message-id: <200006141158.MAA16390@sheesh.cygnus.co.uk>
References: <200006140925.LAA01558@biferten.ma.tech.ascom.ch>
X-SW-Source: 2000-06/msg00140.html

>>>>> "Andrew" == Andrew Lunn <andrew.lunn@ascom.ch> writes:

    Andrew> Unfortunally this only works for 1.3.x. 1.2.x does not have the
    Andrew> version info, just a #define if the package is included. 

    Andrew> My problem is 1.2.x defines

    Andrew> #define CYGPKG_IO_SERIAL

    Andrew> and 1.3.x defines

    Andrew> #define CYGPKG_IO_SERIAL v1_3_5
    Andrew> #define CYGPKG_IO_SERIAL_v1_3_5

    Andrew> and i want something which says

    Andrew> #if CYGPKG_IO_SERIAL > v1.2
    Andrew> new serial code fragment
    Andrew> #else
    Andrew> old serial code fragment
    Andrew> #endif

    Andrew> Any ideas anyone?

I do not think there is any easy way of achieving this at present. The
C preprocessor can only do numerical comparisons. Version numbers can
be much more complicated than just a simple number, so trying to use
the > or < operators is not going to work.

What might be possible is for the configuration tools to generate
additional #define's along the lines of:

#define CYGPKG_IO_SERIAL v1_3_5
#define CYGPKG_IO_SERIAL_VERSION_MAJOR 1
#define CYGPKG_IO_SERIAL_VERSION_MINOR 3
...

Some other systems like Tcl already do this, updating the exported
header file by hand for every release and every snapshot. In the CDL
world this could be automated.

I am not quite sure what to call the versioning levels after major or
minor, there could be any number of these. Also versions may include
letters or text, e.g. 1.3.5beta, and attempting to use C preprocessor
operators on 5beta will probably give a strange compiler error
message. There could also be problems if packages try to define
options with those names.

Arguably the correct solution is a more powerful C preprocessor, but
that is not likely to happen any time soon.

Bart