(wishlist) Automated lib-config script generation

[Roger Leigh]

Nowadays, many shared libraries include a -config script e.g. libgtk
has a gtk-config script, and a companion m4 macro AM_PATH_GTK.  The
header also has version information embedded in it, as does the
library itself:

#define <LIB>_MAJOR_VERSION       (@<LIB>_MAJOR_VERSION@)
#define <LIB>_MINOR_VERSION       (@<LIB>_MINOR_VERSION@)
#define <LIB>_MICRO_VERSION       (@<LIB>_MICRO_VERSION@)
#define <LIB>_CURRENT_INTERFACE   (@<LIB>_CURRENT_INTERFACE@)
#define <LIB>_BINARY_AGE          (@<LIB>_BINARY_AGE@)
#define <LIB>_INTERFACE_AGE       (@<LIB>_INTERFACE_AGE@)
#define <LIB>_CHECK_VERSION(major,minor,micro) \
  (<LIB>_MAJOR_VERSION >  (major) || \
  (<LIB>_MAJOR_VERSION == (major) && <LIB>_MINOR_VERSION >
#(minor)) || \
  (<LIB>_MAJOR_VERSION == (major) && <LIB>_MINOR_VERSION ==
#(minor) && \
   <LIB>_MICRO_VERSION >= (micro)))

There is much duplication of code here.  Anyone wishing to use this
scheme must duplicate the script and then amend it for their use, and
also convert the m4 macro as well, to AM_PATH_<LIB>.  libtool could be
used to automate this.  Currently I maintain the gimp-print build
scripts, and have AM_PATH_GIMPPRINT and gimpprint-config based on the
gtk equivalents.

To remove the need for m4 macro duplication, a single macro could be
used instead.  E.g.:

AC_PATH_LIB(libname, minimum_version, header, config-script)
where libname is the name of the library to check for e.g. gtk, gimp.
      minimum version is the lowest version to allow
      header is the header to include when compiling the test program
        (default libname/libname.h)
      script is the config script to run (default libname-config)

Duplication of the config scripts is unavoidable, as information such
as library location, libraries to link against, and header locations
are hard-coded into them.  However, an m4 macro could be used to
generate them.  E.g.:

AC_LIB_CONFIG(libname, location)
this would generate the script libname-config in the specified
location in the source tree.  The following variables would be used in
generating the file:

<LIB>_MAJOR_VERSION
<LIB>_MINOR_VERSION
<LIB>_MICRO_VERSION
<LIB>_CURRENT_INTERFACE
<LIB>_BINARY_AGE
<LIB>_INTERFACE_AGE

<LIB>_DEFAULT_VERSION  (default minimum_version)
<lib>_cflags           (clags with -I$(prefix)/include etc.
<lib>_libs             (libs with -L$(prefix/lib) and also -llibname
                        and other libraries the library depends upon)
Some of these could also be determined automatically if no variable is
defined, except for the library dependencies.  The macro could contain
a generic config script which it parses with sed (or generates a .in
version of the script, which is then processed by config.status).

The script could be installed with a bin_SCRIPTS directive to
automake.

I'm not sure if an m4 macro is the most appropriate way to do this.
Another way would be to have an LTSCRIPTS automake primary e.g.
bin_LTSCRIPTS=libname-config, although this is probably not as good.


These are just a few ideas I had to make this better.

Regards,
Roger


-- 
Roger Leigh ** Registration Number: 151826, http://counter.li.org **
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