To-do list for xgawk enhancements:


Done:

- Add AWKLIBPATH with default pointing to ${libexecdir}/$PACKAGE/$VERSION

- Change default shared library extension from ".so" to ".$shlibext"

- Patch build infrastructure so that the current code in the
  extension subdirectory gets built and installed into the default $AWKLIBPATH
  location.

- Implement @load

- Patch ERRNO handling to create a simple API for use by extensions:
   extern void update_ERRNO_int(int)
   enum errno_translate { TRANSLATE, DONT_TRANSLATE };
   extern void update_ERRNO_string(const char *string, enum errno_translate);
   extern void unset_ERRNO(void);

- Add valgrind-noleak target.

- Fix minor bug in fork extension, and add wait function.

- Patch filefuncs extension to read symbolic links more robustly.

- Add shared library tests.


To do (not necessarily in this order):

- Enhance extension/fork.c waitpid to allow the caller to specify the options.
  And add an optional array argument to wait and waitpid in which to return
  exit status information.

- Maybe add more shared library tests.

- Figure out how to support xgawk on platforms such as Cygwin where a DLL
  cannot be linked with unresolved references.  There are currently 3
  possible solutions:
    1. Restructure gawk as a stub calling into a shared library.
    2. Move a subset of gawk interfaces into a shared library that can be
       called by extensions.
    3. Change the interface between gawk and extensions so that gawk will
       pass a pointer to a structure into dlload that contains the addresses
       of all variables and functions to which the extension may need access.

- Enable default ".awk" search in io.c:find_source().  The simple change
  is to add this code inline in io.c:
      #ifndef DEFAULT_FILETYPE
      #define DEFAULT_FILETYPE ".awk"
      #endif

- Fix lint complaints about shared library functions being called without
  having been defined.  For example, try:
     gawk --lint -lordchr 'BEGIN {print chr(65)}'
     gawk: warning: function `chr' called but never defined
     A
  In ext.c, make_builtin needs to call awkgram.y:func_use.  If done naively,
  I think this would result in complaints about shared library functions
  defined but not used.  So there should probably be an enhancement to func_use
  and ftable to indicate if it's a shared library function.

- Develop a libgawk shared library for use by extensions.  In particular,
  a few existing extensions use a hash API for mapping string handles to
  structures.  In xgawk, we had this API inside array.c, but it probably
  belongs in a separate libgawk shared library:

  typedef struct _strhash strhash;
  extern strhash *strhash_create P((size_t min_table_size));
  /* Find an entry in the hash table.  If it is not found, the insert_if_missing
     argument indicates whether a new entry should be created.  The caller
     may set the "data" field to any desired value.  If it is a new entry,
     "data" will be initialized to NULL. */
  extern strhash_entry *strhash_get P((strhash *, const char *s, size_t len,
				       int insert_if_missing));
  typedef void (*strhash_delete_func)(void *data, void *opaque,
				      strhash *, strhash_entry *);
  extern int strhash_delete P((strhash *, const char *s, size_t len,
			       strhash_delete_func, void *opaque));
  extern void strhash_destroy P((strhash *, strhash_delete_func, void *opaque));

- Running "make install" should install the new libgawk shared library
  as well as header files needed to build extensions under /usr/include/gawk.
  The extensions include "awk.h", and that pulls in the following headers
  (according to gcc -M) :
      awk.h config.h custom.h gettext.h mbsupport.h protos.h getopt.h \
      regex.h dfa.h
  Most likely, most of this is not required.  Arnold has suggested 
  creating a smaller header to define the public interface for use by shared
  libraries.  One could imagine having "awk-ext.h" that is included by "awk.h".


Separate projects for major standalone extensions.  Where should these
be hosted?

- Time.  This defines sleep and gettimeofday.   This one is quite trivial,
  and I propose that it be included in the mainline gawk distro.

- XML

- PostgreSQL

- GD

- MPFR.  Is this still useful if MPFR support will be integrated into gawk?


Possible changes requiring (further) discussion:

- Change from dlopen to using the libltdl library (i.e. lt_dlopen).
  This may support more platforms.

- Implement namespaces.  Arnold suggested the following in an email:
  - Extend the definition of an 'identifier' to include "." as a valid character
    although an identifier can't start with it.
  - Extension libraries install functions and global variables with names
    that have a "." in them:  XML.parse(), XML.name, whatever.
  - Awk code can read/write such variables and call such functions, but they
    cannot define such functions
	  function XML.foo() { .. }	# error
    or create a variable with such a name if it doesn't exist. This would
    be a run-time error, not a parse-time error.
  - This last rule may be too restrictive.
  I don't want to get into fancy rules a la perl and file-scope visibility
  etc, I'd like to keep things simple.  But how we design this is going
  to be very important.

- Include a sample rpm spec file in a new packaging subdirectory.

- Patch lexer for @include and @load to make quotes optional.

- Add a -i (--include) option.