[Distutils] Example of "config" command

[Greg Ward]

Oh, here's an example of how easy it is to autoconfigure Python
extensions now.  This is taken from examples/mxdatetime_setup.py;
here're the essentials 'run()' method of the "config_mxDateTime" command
class:

    def run (self):
        have = {}
        have['strftime'] = self.check_func('strftime', ['time.h'])
        have['strptime'] = self.check_func('strptime', ['time.h'])
        have['timegm'] = self.check_func('timegm', ['time.h'])

        define = []
        undef = []
        for name in have.keys(): # ('strftime', 'strptime', 'timegm'):
            macro_name = 'HAVE_' + string.upper(name)
            if have[name]:
                define.append((macro_name, None))
            else:
                undef.append(macro_name)

Note that the bulk of the code is the bureaucracy of figuring out which
macros to define, ie. generateing HAVE_STRFTIME and friends.  Obviously
this could (and should) be taken care of by the standard "config"
command; we'll get there!

Here's the output of "setup.py config" (very noisy because --noisy and
--dump-source are both enabled by default for now):

  running config
  compiling '_configtest.c':
  #include <time.h>

  int main () {
    strftime;
  }
  gcc -c -g -O2 -fPIC _configtest.c -o _configtest.o
  gcc _configtest.o -o _configtest
  success!
  removing: _configtest.c _configtest.o _configtest
  compiling '_configtest.c':
  #include <time.h>

  int main () {
    strptime;
  }
  gcc -c -g -O2 -fPIC _configtest.c -o _configtest.o
  _configtest.c: In function `main':
  _configtest.c:4: `strptime' undeclared (first use in this function)
  _configtest.c:4: (Each undeclared identifier is reported only once
  _configtest.c:4: for each function it appears in.)
  failure.
  removing: _configtest.c _configtest.o
  compiling '_configtest.c':
  #include <time.h>

  int main () {
    timegm;
  }
  gcc -c -g -O2 -fPIC _configtest.c -o _configtest.o
  gcc _configtest.o -o _configtest
  success!
  removing: _configtest.c _configtest.o _configtest
  macros to define: [('HAVE_STRFTIME', None), ('HAVE_TIMEGM', None)]
  macros to undefine: ['HAVE_STRPTIME']

Note that ('HAVE_STRFTIME', None) means "-DHAVE_STRFTIME" -- i.e. define
the macro without any particular value.  No, I don't know why
'strptime()' isn't showing up, but at least it demonstrates a failure
case.

        Greg
-- 
Greg Ward - geek-on-the-loose                           gward@python.net
http://starship.python.net/~gward/
Save energy: be apathetic.