Changed how compiler.preprocess() is compared to the default impl

Author: OCopping

src/setuptools_dso/compiler.py

@@ -90,8 +90,9 @@ def new_compiler(**kws):
         if not compiler.initialized: # extra super lazy initialization...
             compiler.initialize()    # populates self.cc among others
 
-        if compiler.__class__.preprocess is CCompiler.preprocess:
-            # default impl. is a no-op...
+        # Checks if the compiler's preprocess is a the same as CCompiler's as...
+        if compiler.__class__.preprocess.__code__ == CCompiler.preprocess.__code__:
+            # ... the default impl. in CCompiler is a no-op...
             compiler.preprocess = partial(_msvc_preprocess, compiler)
 
         if getattr(compiler, 'preprocessor', None) is None: