* Re: Conditonal compilation
1996-04-02 0:00 Conditonal compilation Peter Hermann
@ 1996-04-02 0:00 ` Laurent Guerby
1996-04-02 0:00 ` Robert A Duff
1996-04-03 0:00 ` Laurent Guerby
1 sibling, 1 reply; 5+ messages in thread
From: Laurent Guerby @ 1996-04-02 0:00 UTC (permalink / raw)
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Peter Hermann writes
: Are there any portable means for conditional compilation in Ada?
: How many?
: (e.g. to circumvent Ada95 constructs)
You can use a boolean or enumeration constant defined in a
"portability" (hum, macros are not so far ;-) package, together with
"if" or "case" statements and let the optimization to the compiler.
That's the cleanest way I know of doing it (preserves the full
semantic of Ada, macros are far away ;-).
If your "construct" is a compilation unit, you can use the pragma
Source_File_Name which is a GNAT specific pragma (for now), and the
gnat.adc file (the place for configuration pragmas with GNAT, I don't
know for other compilers), and provide different bodies. Example :
--------- X11 support
-- If you want to have X11 support, and to use the -w, --window command
-- line option, uncomment the following pragma. You'll also need to check
-- the documentation of DART about the X-Binding before compiling.
-- pragma Source_File_Name --%x11
-- (Unit_Name => Images.Display, --%x11
-- Body_File_Name => "x11.images-display.adb"); --%x11
(The "--%x11" is here for Makefile easy-auto-configuration-sed
hacks.) Just provide a dummy images-display.adb that raises an
"Unimplemented" exception when a routine is called. We used this
method for X11/no X11 stuff and tasking/no tasking stuff in the DART
project (not released yet).
But it can easily be generalized, and if the pragma
Source_File_Name is adopted by other vendors (I hope so), it will
provide a clean solution (together with boolean/enumerates) to most
configuration problems *staying in the Ada 95 language*, without
specific Makefiles everywhere (horrors most of the time, if there's
more than one target).
Ada can be a portable language without too much external tools
(like preprocessors ands Makefiles) ;-).
Hope this helps,
--
-- Laurent Guerby, student at Telecom Bretagne (France), Team Ada
-- "Use the Source, Luke. The Source will be with you, always (GPL)"
-- http://www-eleves.enst-bretagne.fr/~guerby/ (GATO Project)
-- Try GNAT, the GNU Ada 95 compiler (ftp://cs.nyu.edu/pub/gnat)
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Conditonal compilation
1996-04-02 0:00 Conditonal compilation Peter Hermann
1996-04-02 0:00 ` Laurent Guerby
@ 1996-04-03 0:00 ` Laurent Guerby
1996-04-03 0:00 ` Peter Hermann
1 sibling, 1 reply; 5+ messages in thread
From: Laurent Guerby @ 1996-04-03 0:00 UTC (permalink / raw)
Robert A Duff writes
: In article <4xrau6d0l6.fsf@leibniz.enst-bretagne.fr>,
: Laurent Guerby <Laurent.Guerby@enst-bretagne.fr> wrote:
: >-- pragma Source_File_Name --%x11
: >-- (Unit_Name => Images.Display, --%x11
: >-- Body_File_Name => "x11.images-display.adb"); --%x11
: >
: > (The "--%x11" is here for Makefile easy-auto-configuration-sed
: >hacks.) ...
:
: Looks like macro preprocessing, to me.
You're right saying it looks like a macro processing hack, since I
added it for Makefile lovers. The "--%x11" is here to allow an user to
configure the software without editing the Ada file (to be honnest,
it's to simplify the regexps in the Makefile, and to avoid the use of
m4 and configure for such a simple thing ;-). In this case, I added
the Makefile only for the release. And here is the main target :
# targets
all:
@echo "Please check the README file before compiling."
@echo "Available targets:"
@echo " clean"
@echo " distclean"
@echo " strip"
@echo " dart"
@echo " true-dart"
@echo " use-default"
@echo " use-x11"
@echo " dont-use-x11"
@echo " use-tasking"
@echo " dont-use-tasking"
;-).
But, the prefered way to configure the software is to edit the
configuration file by hand, commenting out such declaration (with
GNAT, in the gnat.adc file), staying in the Ada world.
That's like editing config.h, but there's no macro at all, and no
ifdefs at any place in the entire source. By default, the software
will work on every platform where you can get a working Ada 95
compiler without any macro, and any ifdef. If you want to take
advantage of tasking or X11, you have to comment out one declaration
each time in one single file.
BTW, If you find any simpler way of configuring software, please
tell us ;-).
: > Ada can be a portable language without too much external tools
: >(like preprocessors ands Makefiles) ;-).
See above ;-)
: - Bob
--
-- Laurent Guerby, student at Telecom Bretagne (France), Team Ada
-- "Use the Source, Luke. The Source will be with you, always (GPL)"
-- http://www-eleves.enst-bretagne.fr/~guerby/ (GATO Project)
-- Try GNAT, the GNU Ada 95 compiler (ftp://cs.nyu.edu/pub/gnat)
^ permalink raw reply [flat|nested] 5+ messages in thread