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SCons / FlexibleLinkCom

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Goal: to have a more flexible LINKCOM, so that we can put options in any order. Right now, we are force to have LINKFLAGS LIBPATH LIBS. In particular, if we want to put linkflags between libs, this is not possible right now wo rewrwiting link actions.

None of below is meant as a prototype: this is just to show the basic concept.

import SCons                                                                              
from SCons.Defaults import _stripixes, _concat                                            

# This dict of func is just a (really) poor-man replacement for  scons                    
# interpolation. In real life, of course, the scons scheme should be used.                
def interpolate_lib(libs, env):                                                           
    return _stripixes(env['LIBLINKPREFIX'], libs,                                         
                      env['LIBLINKSUFFIX'], env['LIBPREFIXES'],                           
                      env['LIBSUFFIXES'], env)                                            

def interpolate_libpath(libpaths, env):                                                   
    return _concat(env['LIBDIRPREFIX'], libpaths, env['LIBDIRSUFFIX'], env,               
                      env['RDirs'], None, None)                                           

_INTERPOLATE = {'LIBS' : interpolate_lib,                                                 
        'LIBPATH': interpolate_libpath,                                                   
        'LINKFLAGS': lambda x, y: x}                                                      

class Framework:                                                                          
    _keys = {'LIBPATH': None, 'LIBS': None, 'LINKFLAGS': None}                            
    def __init__(self):                                                                   
        self._data = []                                                                   

    def append(self, key, value):                                                         
        # XXX: handling non valid construction variables ?                                
        assert key in self._keys                                                          

        # XXX: of course, this should be handled correctly too                            
        assert SCons.Util.is_List(value)                                                  

        self._data.append((key, value))                                                   

    def subst(self, env):                                                                 
        intp = []                                                                         
        # XXX: I should see how scons interpolation works                                 
        for item in self._data:                                                           
            key = item[0]                                                                 
            val = item[1]                                                                 
            intp.extend(_INTERPOLATE[key](val, env))                                      

        return ' '.join(intp)                                                             

class Bstatic:                                                                            
    def __init__(self, lib):                                                              
        f = Framework()                                                                   

        # XXX: This is tool specific (e.g. gnu ld here)                                   
        # Maybe this could be handled at the tool level, be defining pre/post             
        # flag ? But does this catpure all way of doing it (MS platforms ?) ?             
        f.append('LINKFLAGS', ['-Wl,-Bstatic'])                                           
        f.append('LIBS', lib)                                                             
        f.append('LINKFLAGS', ['-Wl,-Bshared'])                                           

        self._f = f                                                                       

    def subst(self, env):                                                                 
        return self._f.subst(env)                                                         

Which would be used in :

from framework import interpolate_lib, interpolate_libpath, Framework, Bstatic

env = Environment()

# Simple example with libpath + lib (not useful here, but anyway)
f1 = Framework()

f1.append('LIBPATH', ['/opt/bar'])
f1.append('LIBS', ['bar'])

print f1.subst(env)

# Simple example to wrap a lib to link statically
f2 = Bstatic(["foo"])

print f2.subst(env)

# Simple example to add two libraries: this way, of foo in present in /opt/bar
# and /opt/foo, foo in /opt/foo will be picked up first
f3 = Framework()
f3.append('LIBPATH', ['/opt/foo'])
f3.append('LIBS', ['foo'])
f3.append('LIBPATH', ['/opt/bar'])
f3.append('LIBS', ['bar'])

print f3.subst(env)

# More complicated example
f4 = Framework()
f4.append('LIBPATH', ['/opt/foo'])
f4.append('LINKFLAGS', ['-Wl,--rpath-link=/opt/foo'])
f4.append('LIBS', ['foo'])
f4.append('LIBPATH', ['/opt/bar'])
f4.append('LINKFLAGS', ['-Wl,--rpath-link=/opt/bar'])
f4.append('LIBS', ['bar'])
f4.append('LINKFLAGS', ['-xlic_lib=foobar'])

print f4.subst(env)

Which would print:

-L/opt/bar -lbar
-Wl,-Bstatic -lfoo -Wl,-Bshared
-L/opt/foo -lfoo -L/opt/bar -lbar
-L/opt/foo -Wl,--rpath-link=/opt/foo -lfoo -L/opt/bar -Wl,--rpath-link=/opt/bar -lbar -xlic_lib=foobar