[m-rev.] patch: pragma import on il backend

[Peter Ross]

This patch almost gets foreign import/export working on the IL
backend, so I am sending it to the mailing list for prosterity.

The main problem is that is that we rather hackily use MC++ like it
could just simply be used for C.  This is not true.

Index: foreign.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/foreign.m,v
retrieving revision 1.22
diff -u -r1.22 foreign.m
--- foreign.m	5 Aug 2002 21:46:09 -0000	1.22
+++ foreign.m	10 Dec 2002 17:33:07 -0000
@@ -262,14 +283,9 @@
 			WantedLang = Lang),
 		Bodys0, LangBodys, NotLangBodys).
 	
-foreign__extrude_pragma_implementation([], _PragmaVars,
-	_PredName, _PredOrFunc, _Context, _ModuleInfo0, _Attributes, _Impl0, 
-	_ModuleInfo, _NewAttributes, _Impl) :-
-	unexpected(this_file, "no suitable target languages available").
-
 	% We just use the first target language for now, it might be nice
 	% to try a few others if the backend supports multiple ones.
-foreign__extrude_pragma_implementation([TargetLang | TargetLangs], 
+foreign__extrude_pragma_implementation(TargetLangs, 
 		_PragmaVars, _PredName, _PredOrFunc, _Context,
 		ModuleInfo0, Attributes, Impl0, 
 		ModuleInfo, NewAttributes, Impl) :-
@@ -277,21 +293,57 @@
 
 		% If the foreign language is available as a target language, 
 		% we don't need to do anything.
-	( list__member(ForeignLanguage, [TargetLang | TargetLangs]) ->
+	(
+		list__member(ForeignLanguage, TargetLangs)
+	->
 		Impl = Impl0,
 		ModuleInfo = ModuleInfo0,
 		NewAttributes = Attributes
 	;
-		set_foreign_language(Attributes, TargetLang, NewAttributes),
-		extrude_pragma_implementation_2(TargetLang, ForeignLanguage,
-			ModuleInfo0, Impl0, ModuleInfo, Impl)
+		extrude_pragma_implementation_2(TargetLangs, ForeignLanguage,
+				ModuleInfo0, Impl0,
+				ChosenTargetLang, ModuleInfo1, Impl1)
+	->
+		set_foreign_language(Attributes,
+				ChosenTargetLang, NewAttributes),
+		ModuleInfo = ModuleInfo1,
+		Impl = Impl1
+	;
+		Str = "unable to call " ++
+				foreign_language_string(ForeignLanguage) ++
+				" from any of " ++
+				string__append_list(list__map((func(L) =
+						foreign_language_string(L) ++
+						" "
+					), TargetLangs)),
+		unexpected(this_file, Str)
 	).
 
-
 :- pred extrude_pragma_implementation_2(
+	list(foreign_language)::in, foreign_language::in,
+	module_info::in, pragma_foreign_code_impl::in,
+	foreign_language::out,
+	module_info::out, pragma_foreign_code_impl::out) is semidet.
+
+extrude_pragma_implementation_2([TargetLang | TargetLangs], ForeignLanguage,
+		ModuleInfo0, Impl0, ChosenTargetLang, ModuleInfo, Impl) :-
+	(
+		extrude_pragma_implementation_3(TargetLang, ForeignLanguage,
+				ModuleInfo0, Impl0, ModuleInfo1, Impl1)
+	->
+		ChosenTargetLang = TargetLang,
+		ModuleInfo = ModuleInfo1,
+		Impl = Impl1
+	;
+		extrude_pragma_implementation_2(TargetLangs, ForeignLanguage,
+				ModuleInfo0, Impl0, ChosenTargetLang,
+				ModuleInfo, Impl)
+	).
+
+:- pred extrude_pragma_implementation_3(
 	foreign_language::in, foreign_language::in,
 	module_info::in, pragma_foreign_code_impl::in,
-	module_info::out, pragma_foreign_code_impl::out) is det.
+	module_info::out, pragma_foreign_code_impl::out) is semidet.
 
 	% This isn't finished yet, and we probably won't implement it for C
 	% calling MC++.  For C calling normal C++ we would generate a proxy
@@ -313,61 +365,22 @@
 	Impl = import(NewName, ReturnCode, VarString, no)
 	*/
 
-extrude_pragma_implementation_2(c, managed_cplusplus, _, _, _, _) :-
-	unimplemented_combination(c, managed_cplusplus).
-
-extrude_pragma_implementation_2(c, csharp, _, _, _, _) :-
-	unimplemented_combination(c, csharp).
-
-extrude_pragma_implementation_2(c, il, _, _, _, _) :-
-	unimplemented_combination(c, il).
-
-extrude_pragma_implementation_2(c, c, ModuleInfo, Impl, ModuleInfo, Impl).
-
+extrude_pragma_implementation_3(c, c, ModuleInfo, Impl, ModuleInfo, Impl).
 
 		% Don't do anything - C and MC++ are embedded inside MC++
 		% without any changes.
-extrude_pragma_implementation_2(managed_cplusplus, managed_cplusplus,
+extrude_pragma_implementation_3(managed_cplusplus, managed_cplusplus,
 	ModuleInfo, Impl, ModuleInfo, Impl).
 
-extrude_pragma_implementation_2(managed_cplusplus, c,
+extrude_pragma_implementation_3(managed_cplusplus, c,
 	ModuleInfo, Impl, ModuleInfo, Impl).
 
-extrude_pragma_implementation_2(managed_cplusplus, csharp, _, _, _, _) :-
-	unimplemented_combination(managed_cplusplus, csharp).
-
-extrude_pragma_implementation_2(managed_cplusplus, il, _, _, _, _) :-
-	unimplemented_combination(managed_cplusplus, il).
-
-
-
-extrude_pragma_implementation_2(csharp, csharp,
+extrude_pragma_implementation_3(csharp, csharp,
 	ModuleInfo, Impl, ModuleInfo, Impl).
 
-extrude_pragma_implementation_2(csharp, c, _, _, _, _) :-
-	unimplemented_combination(csharp, c).
-
-extrude_pragma_implementation_2(csharp, managed_cplusplus, _, _, _, _) :-
-	unimplemented_combination(csharp, managed_cplusplus).
-
-extrude_pragma_implementation_2(csharp, il, _, _, _, _) :-
-	unimplemented_combination(csharp, il).
-
-
-extrude_pragma_implementation_2(il, il,
+extrude_pragma_implementation_3(il, il,
 	ModuleInfo, Impl, ModuleInfo, Impl).
 
-extrude_pragma_implementation_2(il, c, _, _, _, _) :-
-	unimplemented_combination(il, c).
-
-extrude_pragma_implementation_2(il, managed_cplusplus, _, _, _, _) :-
-	unimplemented_combination(il, managed_cplusplus).
-
-extrude_pragma_implementation_2(il, csharp, _, _, _, _) :-
-	unimplemented_combination(il, csharp).
-
-
-
 :- pred unimplemented_combination(foreign_language::in, foreign_language::in)
 		is erroneous.
 
Index: modules.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/modules.m,v
retrieving revision 1.255
diff -u -r1.255 modules.m
--- modules.m	10 Dec 2002 07:38:09 -0000	1.255
+++ modules.m	10 Dec 2002 17:33:09 -0000
@@ -4834,6 +4850,14 @@
 			)
 		)
 	;	
+		% XXX petdr
+		Pragma = import(_, _, _, _, _),
+		Lang = managed_cplusplus,
+		list__member(Lang, BackendLangs)
+	->
+		Info = Info0 ^ used_foreign_languages :=
+	    		set__insert(Info0 ^ used_foreign_languages, Lang)
+	;
 		% XXX `pragma export' should not be treated as
 		% foreign, but currently mlds_to_gcc.m doesn't
 		% handle that declaration, and instead just
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