add compatibility module and make use of CPPYY_BACKEND_LIBRARY if set

doc/source/installation.rst

@@ -22,18 +22,23 @@ To use them, tell ``pip``::
  $  pip install --extra-index https://cern.ch/wlav/wheels cppyy
 
 PyPy 5.7 and 5.8 have a built-in module ``cppyy``.
-You can still install the ``cppyy`` package (or, alternatively, just
-``cppyy-backend``), but the built-in takes precedence.
-To use ``cppyy`` without further setting environment variables, simply load
-the backend explicitly, before importing ``cppyy``::
+You can still install the ``cppyy`` package, but the built-in module takes
+precedence.
+To use ``cppyy``, first import a compatibility module::
 
  $ pypy
  [PyPy 5.8.0 with GCC 5.4.0] on linux2
- >>>> from cppyy_backend import loader
- >>>> c = loader.load_cpp_backend()
- >>>> import cppyy
+ >>>> import cppyy_compat, cppyy
  >>>>
 
+You will have to set ``LD_LIBRARY_PATH`` appropriately if you get an
+``EnvironmentError`` (it will indicate the needed directory).
+
+Note that your python interpreter (whether CPython or ``pypy-c``) may not have
+been linked by the C++ compiler.
+This can lead to problems during loading of C++ libraries and program shutdown.
+In that case, re-linking is highly recommended.
+
 Older versions of PyPy (5.6.0 and earlier) have a built-in ``cppyy`` based on
 `Reflex`_, which is less feature-rich and no longer supported.
 However, both the :doc:`distribution tools <distribution>` and user-facing

python/cppyy/_pypy_cppyy.py

@@ -1,6 +1,21 @@
 """ PyPy-specific touch-ups
 """
 
+import sys
+
+# pypy-c may not have been linked with C++; force its loading before
+# doing anything else (note that not linking with C++ spells trouble
+# anyway for any C++ libraries ...)
+if 'linux' in sys.platform and 'GCC' in sys.version:
+    # TODO: check executable to see whether linking indeed didn't happen
+    import ctypes
+    try:
+        stdcpp = ctypes.CDLL('libstdc++.so', ctypes.RTLD_GLOBAL)
+    except Exception:
+        pass
+# TODO: what if Linux/clang and what if Mac?
+
+import os
 from cppyy_backend import loader
 
 __all__ = [
@@ -12,6 +27,7 @@
 # first load the dependency libraries of the backend, then
 # pull in the built-in low-level cppyy
 c = loader.load_cpp_backend()
+os.environ['CPPYY_BACKEND_LIBRARY'] = c._name
 import _cppyy as _backend     # built-in module
 _backend._cpp_backend = c
 

python/cppyy_compat/__init__.py

@@ -0,0 +1,47 @@
+"""Compatibility layer for PyPy 5.8 and 5.7
+"""
+
+def pypy58_57_compat():
+    import imp, os
+
+  # first load and move the builtin cppyy module
+    if not 'cppyy' in sys.modules:
+        try:
+            olddir = os.getcwd()
+            from cppyy_backend import loader
+            c = loader.load_cpp_backend()
+          # move to the location of the backend, just in case '.' is
+          # in the dynloader's path
+            os.chdir(os.path.dirname(c._name))
+            imp.init_builtin('cppyy')
+        except ImportError:
+            raise EnvironmentError('"%s" missing in LD_LIBRARY_PATH' %\
+                                   os.path.dirname(c._name))
+        finally:
+            os.chdir(olddir)
+
+    sys.modules['_cppyy'] = sys.modules['cppyy']
+    del sys.modules['cppyy']
+
+  # now locate and load the pip cppyy module
+    decdir = os.path.join(os.path.dirname(__file__), os.path.pardir)
+    for path in sys.path:     # walk over sys.path skips builtins
+        try:
+            fp, pathname, description = imp.find_module('cppyy', [path])
+            sys.modules['cppyy'] = imp.load_module('cppyy_', fp, pathname, description)
+            break
+        except ImportError:
+            pass
+
+  # copy over the _cppyy functions into cppyy
+    old = sys.modules['_cppyy']
+    new = sys.modules['cppyy']
+    for name in dir(old):
+        if not hasattr(new, name):
+            setattr(new, name, getattr(old, name))
+
+import sys
+version = sys.pypy_version_info
+if version[0] == 5 and 6 < version[1] <= 8:
+    pypy58_57_compat()
+del version, sys

setup.py

@@ -14,8 +14,10 @@
     version = sys.pypy_version_info
     if version[0] == 5 and version[1] <= 8:
         requirements = ['cppyy-backend<0.3']
+        add_pkg = ['cppyy', 'cppyy_compat']
     else:
         requirements = ['cppyy-backend']
+        add_pkg = ['cppyy']
 except ImportError:
     requirements = ['CPyCppyy']
 
@@ -60,5 +62,5 @@
     keywords='C++ bindings',
 
     package_dir={'': 'python'},
-    packages=find_packages('python'),
+    packages=find_packages('python', include=add_pkg),
 )