Re: Guile API for foreign languages: proposing SCM scm_list_0(void)

[Andy Wingo <wingo@pobox.com>]

Hi Alexei,

On Mon 02 Jul 2012 13:11, Alexei Matveev <alexei.matveev@gmail.com> writes:

> To raise this question again: I ended up with a wrapper
> function for a Fortran project equivalent to the scm_list_0()
> quoted below. The reason is accessing macros from languages
> other than C is cumbersome.
>
> Contrary to scm_from/to_int, scm_is_*  and other macros
> adding this as a funciton one is a no-brainer, since it would
> be a new API call and raises no compatibility concerns.

Apologies for ignoring you.  I think that the thought that if we wanted
to follow through the logic of making Guile's C API available to non-C
languages, we should do so either all the way or not at all.

Each additional function added to Guile's ABI imposes additional cost in
runtime memory, ELF symbol resolution, and (to a degree) startup time,
without providing any benefits to C users.  On the other hand, if we are
only talking about 2 functions (say), then clearly we should do it.  So
part of the question is, how much work are we talking about?

I grepped the header files for lines starting with "#define SCM_",
munged out the name of the macro and sorted them for uniqueness.  That
was around 1200 macros.  I filtered out certain kinds of macros:

  * those ending in _H (header guards)
  * those starting with SCM_I_ (internal macros)
  * those containing _BIT (implementation details)
  * SCM_VALIDATE_ macros (there are corresponding C procedures)

That left me with about 900 macros.

I then filtered out all macros that had a corresponding C binding.  For
example, SCM_CAR has a C procedure, `scm_car'.  That left me with about
780 macros.

Finally, from this list, I filtered out those symbols that did not
appear in our documentation.  That resulted in the following 77 symbols:

    SCM_ALLOW_INTS
    SCM_ARG1
    SCM_ARG2
    SCM_ARG3
    SCM_ARG4
    SCM_ARG5
    SCM_ARG6
    SCM_ARG7
    SCM_ARGn
    SCM_ASSERT_TYPE
    SCM_BOOL_F
    SCM_BOOL_T
    SCM_BYTEVECTOR_CONTENTS
    SCM_CELL_OBJECT
    SCM_CELL_OBJECT_0
    SCM_CELL_OBJECT_1
    SCM_CELL_TYPE
    SCM_CELL_WORD
    SCM_CELL_WORD_0
    SCM_CELL_WORD_1
    SCM_DEFER_INTS
    SCM_ELISP_NIL
    SCM_EOF_VAL
    SCM_EOL
    SCM_FRAME_DATA_ADDRESS
    SCM_FRAME_LOWER_ADDRESS
    SCM_FRAME_UPPER_ADDRESS
    SCM_GLOBAL_KEYWORD
    SCM_GLOBAL_VARIABLE
    SCM_GLOBAL_VARIABLE_INIT
    SCM_GPROC
    SCM_HOOKP
    SCM_IMP
    SCM_NEWSMOB
    SCM_NEWSMOB2
    SCM_NEWSMOB3
    SCM_PTAB_ENTRY
    SCM_PTOBNUM
    SCM_REGISTER_PROC
    SCM_RETURN_NEWSMOB
    SCM_RETURN_NEWSMOB2
    SCM_RETURN_NEWSMOB3
    SCM_SET_CELL_OBJECT
    SCM_SET_CELL_OBJECT_0
    SCM_SET_CELL_OBJECT_1
    SCM_SET_CELL_TYPE
    SCM_SET_CELL_WORD
    SCM_SET_CELL_WORD_0
    SCM_SET_CELL_WORD_1
    SCM_SET_SMOB_DATA
    SCM_SET_SMOB_DATA_2
    SCM_SET_SMOB_DATA_3
    SCM_SET_SMOB_FLAGS
    SCM_SET_SMOB_OBJECT
    SCM_SET_SMOB_OBJECT_2
    SCM_SET_SMOB_OBJECT_3
    SCM_SIMPLE_VECTOR_LENGTH
    SCM_SIMPLE_VECTOR_REF
    SCM_SIMPLE_VECTOR_SET
    SCM_SMOB_DATA
    SCM_SMOB_DATA_2
    SCM_SMOB_DATA_3
    SCM_SMOB_FLAGS
    SCM_SMOB_OBJECT
    SCM_SMOB_OBJECT_2
    SCM_SMOB_OBJECT_2_LOC
    SCM_SMOB_OBJECT_3
    SCM_SMOB_OBJECT_3_LOC
    SCM_SMOB_OBJECT_LOC
    SCM_SMOB_PREDICATE
    SCM_TICK
    SCM_UNBNDP
    SCM_UNBOUND
    SCM_UNDEFINED
    SCM_UNSPECIFIED
    SCM_VARIABLE_INIT

The next step would be to manually check which of these symbols are
actually necessary.  Perhaps I can leave this job to someone else :)

Regards,

Andy
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