"main" function in GNU make internals

[Ewan Delanoy]

   I am a little curious about GNU-make internals, so what I would
   like to do is the following : invoke make not the usual way, but by
   viewing the source as a project in my favorite C debugger, and
   (presumably) call a certain "main" function (or whatever it is called)
   taking as parameter a makefile name and a target name.
   I browsed a few files in the source distribution at random without
   finding
   what I was looking for. Where is this "main" function ?