RE: Questions: ./config.h.in & ./windows-NT/config.h.in

[Conrad T. Pino]

Hi Derek,

> From: Derek Robert Price
> 
> >>copy config.h.in to windows-NT/config.h.in
> >>foreach #define in windows-NT/config.h.in.in
> >>    find corresponding #undef in windows-NT/config.h.in
> >>       (if not present, print warning)
> >>    replace line with current #define
> >>end foreach
> >>foreach #undef in config.h.in
> >>    find corresponding #define or #undef in windows-NT/config.h.in.in
> >>       (if not present, print warning)
> >>end foreach
> >
> >========================================
> >OK, the concept looks sound but there are problems in "./config.h.in"
> >that IMO can be worked out.
> >--------------------
> >This is a good example that needs elaboration:
> >
> >    /* ... */
> >    #undef FILESYSTEM_BACKSLASH_IS_FILE_NAME_SEPARATOR
> >
> >    #if FILESYSTEM_ACCEPTS_DRIVE_LETTER_PREFIX
> >    # define FILESYSTEM_PREFIX_LEN(Filename) \
> >      ((Filename)[0] && (Filename)[1] == ':' ? 2 : 0)
> >    #else
> >    # define FILESYSTEM_PREFIX_LEN(Filename) 0
> >    #endif
> >
> >IMO conditional #define warrants special attention along the lines of
> >"windows-NT/config.h.in.in" saying something about
> 
> No it doesn't.  Reread my pseudo-code.  I was very specific where I
> mentioned #undef and #define.

I don't advise giving me code (pseudo or real) without expecting
it *may* come out looking very different.  What was provided was
very good and much appreciated.

Note file names I use here are values useable for builds other than
Windows and are used to illustrate such use.  Final script implements
in manner that will be easy to tailor.

>    1. Again, the entire config.h.in is copied to
>       windows-NT/config.h.in, including your conditional constructs.

This is out of order if implemented as stated.  I plan:

        1. Read "windows-NT/config.h.in" to:

                1.1 Collect list of #define/#undef statements.

                1.2 Report duplicate #define/#undef statements.

        2. Copy "config.h.in" to temporary file "windows-NT/config.h.tmp"
        while doing:

                2.1 Collect list of #define/#undef statements.

                2.2 Report duplicate #define/#undef statements.

                2.3 Replace #undef with #define collected in Step 1.

        3. Append optional "windows-NT/config.h.end" to temporary file
        "windows-NT/config.h.tmp" and close temporary file.

        4. Compare temporary file "windows-NT/config.h.tmp" to output
        file "windows-NT/config.h" stopping on first difference.

>    2. #defines in windows-NT/config.h.in.in are search/replaced over
>       #undefs in the new windows-NT/config.h.in with a warning if
>       there is no #undef to replace.
>    3. #undefs in config.h.in without corresponding #defines or #undefs
>       in windows-NT/config.h.in.in cause warnings.  (Note that #undefs
>       in windows-NT/config.h.in.in are ignored until this step.  They
>       are intended to be used to suppress warnings if config.h.in
>       happens to ever contain a conditional with an #undef inside.)

"(Note..." in your Step 3 was very helpful.  Thank you.  I continue:

        5. Sort lists from Steps 1 and 2.1 and issue warnings per your
        Steps 2 & 3 using a single pass comparing both lists.

        6. Replace output file with temporary file *only* if different.

> The rule I know that you might not is that if the configure script is
> going to set a #define (or not) at configure time, it will always be
> #undefined in config.h.in.

Definitely helpful.  Thank you.
========================================================
Note tracking conditional nesting level is required to perform my
Steps 1.2 and 2.2 accurately as *helpful* developer aid.
========================================================
I believe we both know there's *no way* we can produce correct output
using the current "windows-NT/config.h.in" as input.  Too much stuff
will be dropped that is *only* in "windows-NT/config.h.in" file.

I assume you have a plan for revising *something* and I'd appreciate
at least an outline.  Perhaps I could contribute if I had a clue.

I'm bet hedging with my Step 3 for a "windows-NT/config.h.end" file
to hold the extra stuff until a better plan is revealed.

I'm bet hedging by copying #define/#undef statements and skipping my
Steps 1.1, 1.2, 2.1 and 2.2 when conditional nesting level > 0 until
the better plan is revealed.

If you're interested I can provide a set of Windows inputs that when
combined with "./config.h.in" will output a *substantially* identical
result to the current set.
========================================================
I'm going to start another thread to exchange the script as work in
progress.  The Subject will be "Perl: config-h.pl - Draft".
========================================================
Thanks again,

> Derek

Conrad