Heap file content

Dear SML/NJ developers and compiler hackers,

I'm trying to get a grasp of SML/NJ's internal workings, especially
with an eye on generating, loading, linking, and executing code.

An answer to the following question would be a first step towards
unraveling the mysteries of the infrastructures of the compiler and
runtime system.

What does a heap file contain?  What is considered 'live' before an
export?

It puzzles me that the heap file generated by ml-build from the
(rather trivial) function

    structure Foo = struct
      fun main(_, _) = 0
    end

and the .cm file

    Library
      structure Foo
    is
      foo.sml

contains several hundred thousand bytes (379840 bytes on my x86-linux
machine).

The ml-build script automatically adds the basis library before
exporting the function.  Does this library become part of the heap?
Does the compiler (which is typically available before a export, at
least if issued from the interactive prompt) become part of the heap?

Is it possible to control what does and what does not go into a heap
file?

-- Morten
________________________________
Morten Rhiger
Computer Science
Roskilde University, Denmark
Homepage: http://www.ruc.dk/~mir


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