[Scons-users] Question about scons

[Guillaume Anciaux]

Dear all,

This is a follow-up on my progression.

Before even working on the repo to place the tools (and other stuff) I
needed to do a few tests for my knowledge and be sure I go in the right
direction.

What I did is I made a tool in a site_scons/site_init.py as a start.
It aims at 'detecting' FFTW with a few options like the required version
for instance. This is what I wrote:

*******************************************************
def fftw(env):
   """A Tool to search for fftw headers and libraries"""

   if env.GetOption('clean'): return
   if 'FFTW_VERSION' not in env: env['FFTW_VERSION'] = "3"
   env['FFTW_VERSION'] = str(env['FFTW_VERSION'])

   if 'FFTW_INCLUDE_DIR' in env:
      env['CXXFLAGS'].append('-I{0}'.format(env['FFTW_INCLUDE_DIR']))
      env['CFLAGS'].append('-I{0}'.format(env['FFTW_INCLUDE_DIR']))

   if 'FFTW_LIBRARY_WISH' not in env:
      env['FFTW_LIBRARY_WISH'] = ['main']
     
   if 'FFTW_LIBRARY_DIR' in env:
      if 'LIBPATH' not in env: env['LIBPATH'] = []
      env['LIBPATH'] += [env['FFTW_LIBRARY_DIR']]
  
   version = env['FFTW_VERSION']
   if version == "2":
      lib_names = {'main':'fftw'}
      inc_names = ['fftw.h']
   else:
      lib_names =
{'main':'fftw3','thread':'fftw3_threads','omp':'fftw3_omp'}
      inc_names = ['fftw3.h']

   conf = Configure(env)

   try:
      lib_names = [lib_names[i] for i in env['FFTW_LIBRARY_WISH']+['main']]
   except:
      print 'Incompatible wishlist {0} from version
{1}'.format(env['FFTW_WISH_LIST'],
                                                               
env['FFTW_VERSION'])
      Exit(1)

   for l in lib_names:
      if not conf.CheckLibWithHeader(l, inc_names, 'c'):
         print 'Did not find FFTW, exiting!'
         Exit(1)
      print env['LIBS']
  
        
   env['FFTW_LIBRARIES'] = lib_names
   env = conf.Finish()
*******************************************************

Thus I have some questions:

- What I wrote also has a configure sequence. But I think this is not
what a tool should do. Correct ?

From what I read you can also make your own configure checks.

- I think the environment extension, which defines a few variables based
on some others, and the 'configure' stage which actually verify that
everything can be accessed are close related pieces of code: can we make
a tool that registers specific configure checks ?

- The configure stage is adding directly what he found to the $LIBS
option. However if I just want to know that everything is here and
manually add to LIBS: can I do that ?


I guess that in the end I would like to be able to write a sequence of
code like:
*********************************
env = Environment(
    tools=['defatult','fftw'],
    FFTW_LIBRARY_WISH = ['thread','omp']
    FFTW_VERSION = ['thread','omp']
)

conf = Configure(env)
conf.CheckFFTW()
conf.Finish()
**********************************


- how to make it explicit that the FFTW tool depends on the 'default'
(since it needs a C/C++ compiler to be used) ?

Thanks for your help.

Best

Guillaume



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