notes on gfortran internals?

[Steve Kargl <sgk at troutmask dot apl dot washington dot edu>]

Does anyone have any notes on gfortran internals?
This includes understanding simple data structures
to the more arcane internals on modules and derives
types.  I can probably flesh out the how, what,
where and why of the expression node and adding a
new intrinsic procedure to gfortran, but modules,
derived types, and partically the entire backend
is opaque.  I'm willing to collate the info into
some form of document, but will probably need some
help with texinfo markup.

PS:  I'm starting to write up the intrinsic procedures
that we support in gfortran.  I have a complete list
of intrinsics up to this past weekend.  The document
will be in alphabetical order for all intrinsic names
and will be something along the lines:

ABS -- Absolute Value

  Class: F95

  Generic intrinsic function: ABS(X)
     where X is INTEGER(KIND=*), REAL(KIND=*), or COMPLEX(kind=*) and
     ABS(X) returns INTEGER(KIND=*) or REAL(KIND=*) depending on the
     type and kind of X.


  Specific intrinsic functions:
     ABS(X) -- yada yada
    DABS(X) -- yada yada
    IABS(X) -- yada yada
    CABS(X) -- yada yada


DABS -- Absolute Value
  See ABS


IARGC -- Number of command line arguments

  Class: Gnu

  Generic intrinsic function: IARGC()
     return the number of command line arguments.  The return type
     and kind is INTEGER(KIND=4).
 
  Specific intrinsic functions: IARGC()
    

I will of course consult the Fortran 2003 standard (the only 
doc I have) and M&R.

-- 
Steve