mercury/compiler/make.module_target.m

%-----------------------------------------------------------------------------%
% Copyright (C) 2002 The University of Melbourne.
% This file may only be copied under the terms of the GNU General
% Public License - see the file COPYING in the Mercury distribution.
%-----------------------------------------------------------------------------%
:- module make__module_target.

:- interface.

:- pred make_module_target(dependency_file::in, bool::out,
	make_info::in, make_info::out, io__state::di, io__state::uo) is det.

	% For make__module_dep_file__write_module_dep_file.
:- pred record_made_target(target_file::in, compilation_task_type::in,
	bool::in, make_info::in, make_info::out,
	io__state::di, io__state::uo) is det.

:- type foreign_code_file
	--->	foreign_code_file(
			foreign_language :: foreign_language,
			target_file :: file_name,
			object_file :: file_name
		).

	% Find the foreign code files generated when a module is processed.
:- pred external_foreign_code_files(module_imports::in,
	list(foreign_code_file)::out, io__state::di, io__state::uo) is det.

%-----------------------------------------------------------------------------%
:- implementation.

:- import_module hlds__passes_aux.

:- pred make_module_target(dependency_file::in, bool::in, bool::out,
	make_info::in, make_info::out, io__state::di, io__state::uo) is det.

make_module_target(TargetFile, Succeeded1, Succeeded1 `and` Succeeded2,
		Info0, Info) -->
	make_module_target(TargetFile, Succeeded2, Info0, Info).

make_module_target(file(_, _) @ Dep, Succeeded, Info0, Info) -->
    dependency_status(Dep, Status, Info0, Info),
    { Succeeded = ( Status = error -> no ; yes ) }.
make_module_target(target(TargetFile) @ Dep, Succeeded, Info0, Info) -->
    dependency_status(Dep, Status, Info0, Info1),
    (
	{ Status = not_considered },
	{ TargetFile = ModuleName - FileType },
	get_module_dependencies(ModuleName, MaybeImports, Info1, Info2),
	(
	    { MaybeImports = no },
	    { Succeeded = no },
	    { Info = Info2 ^ dependency_status ^ elem(Dep) := error }
	;
	    { MaybeImports = yes(Imports) },
	    globals__io_get_globals(Globals),
	    { CompilationTask = compilation_task(Globals, FileType) },
	    (
		% For a target built by processing a Mercury source file,
		% the target for a nested sub-module is produced as a side
		% effect of making the target for the top-level module in
		% the file.
		{ CompilationTask = process_module(_) - _ },
	    	{ Imports ^ source_file_module_name \= ModuleName }
	    ->
		make_module_target(
			target(Imports ^ source_file_module_name - FileType),
			Succeeded, Info2, Info)
	    ;
		{ CompilationTask = CompilationTaskType - _ },
		touched_files(TargetFile, CompilationTaskType,
			TouchedTargetFiles, TouchedFiles, Info2, Info3),
		{ list__foldl(update_target_status(being_built),
			TouchedTargetFiles, Info3, Info4) },

		debug_file_msg(TargetFile, "checking dependencies"),

		{ CompilationTask = process_module(_) - _ ->
		    ModulesToCheck = [ModuleName | Imports ^ nested_children]
		;
		    ModulesToCheck = [ModuleName]
		},

		foldl3_maybe_stop_at_error(Info4 ^ keep_going,
			union_deps(target_dependencies(Globals, FileType)),
			ModulesToCheck, DepsSuccess, set__init,
			DepFiles0, Info4, Info5),
		{ TargetFile = _ - private_interface ->
			% Avoid circular dependencies (the `.int0' files
			% for the nested sub-modules depend on this module's
			% `.int0' file).
			DepFilesToMake = set__to_sorted_list(
				set__delete_list(DepFiles0, 
				make_dependency_list(ModulesToCheck,
					private_interface)))
		;
			DepFilesToMake = set__to_sorted_list(DepFiles0)
		},
		{ DepFiles = set__to_sorted_list(DepFiles0) },

		debug_msg(
		   (pred(di, uo) is det -->
			write_target_file(TargetFile),
			io__write_string(": dependencies:\n"),
			io__write_list(DepFiles, ", ", write_dependency_file),
			io__nl
		    )),

		globals__io_lookup_bool_option(keep_going, KeepGoing),
		( { DepsSuccess = no, KeepGoing = no } ->
			{ Info6 = Info5 },
			{ DepsResult = error }
		;
			make_dependency_files(TargetFile, DepFilesToMake,
				TouchedTargetFiles, TouchedFiles, DepsResult0,
				Info5, Info6),
			{ DepsResult =
				( DepsSuccess = yes -> DepsResult0 ; error ) }
		),
		(
			{ DepsResult = error },
			{ Succeeded = no },
			{ list__foldl(update_target_status(error),
	    			TouchedTargetFiles, Info6, Info) }
		;
			{ DepsResult = out_of_date },
			build_target(CompilationTask, TargetFile, Imports,
				TouchedTargetFiles, TouchedFiles, Succeeded,
				Info6, Info)
		;
			{ DepsResult = up_to_date },
			debug_file_msg(TargetFile, "up to date"),
			{ Succeeded = yes },
			{ list__foldl(update_target_status(up_to_date),
	    			[TargetFile | TouchedTargetFiles],
				Info6, Info) }
		)
	    )
    	)
    ;
	{ Status = up_to_date },
	{ Succeeded = yes },
	{ Info = Info1 }
    ;
	{ Status = being_built },
	{ error(
	"make_module_target: target being built, circular dependencies?") },
	{ Succeeded = no },
	{ Info = Info1 }
    ;
	{ Status = error },
	{ Succeeded = no },
	{ Info = Info1 }
    ).

:- pred make_dependency_files(target_file::in, list(dependency_file)::in,
	list(target_file)::in, list(file_name)::in, dependencies_result::out,
	make_info::in, make_info::out, io__state::di, io__state::uo) is det.

make_dependency_files(TargetFile, DepFilesToMake, TouchedTargetFiles,
		TouchedFiles, DepsResult, Info0, Info) -->
	%
	% Build the dependencies.
	%
	globals__io_lookup_bool_option(keep_going, KeepGoing),
	foldl2_maybe_stop_at_error(KeepGoing, make_module_target,
		DepFilesToMake, MakeDepsSuccess, Info0, Info1),

	%
	% Check that the target files exist.
	%
	list__map_foldl2(get_target_timestamp, TouchedTargetFiles,
			TargetTimestamps, Info1, Info2),
	(
		{ MakeDepsSuccess = no }
	->
		debug_file_msg(TargetFile, "error making dependencies"),
		{ DepsResult = error },
		{ Info = Info2 }
	;
		{ list__member(error(_), TargetTimestamps) }
	->
		debug_file_msg(TargetFile, "target file does not exist"),
		{ DepsResult = out_of_date },
		{ Info = Info2 }
	;
		%
		% Compare the oldest of the timestamps of the touched
		% files with the timestamps of the dependencies.
		%
		list__map_foldl2(get_timestamp_file_timestamp,
			TouchedTargetFiles, TouchedTargetFileTimestamps,
			Info2, Info3),
		list__map_foldl2(get_file_timestamp([dir__this_directory]),
			TouchedFiles, TouchedFileTimestamps, Info3, Info4),
		{ MaybeOldestTimestamp0 = list__foldl(find_oldest_timestamp, 
			TouchedTargetFileTimestamps, ok(newest_timestamp)) },
		{ MaybeOldestTimestamp = list__foldl(find_oldest_timestamp, 
			TouchedFileTimestamps, MaybeOldestTimestamp0) },

		get_file_name(TargetFile, TargetFileName, Info4, Info5),
		check_dependencies(TargetFileName,
			MaybeOldestTimestamp, DepFilesToMake,
			DepsResult, Info5, Info)
	).

%-----------------------------------------------------------------------------%

:- pred build_target(compilation_task_result::in, target_file::in,
	module_imports::in, list(target_file)::in, list(file_name)::in,
	bool::out, make_info::in, make_info::out,
	io__state::di, io__state::uo) is det.

build_target(CompilationTask, TargetFile, Imports, TouchedTargetFiles,
		TouchedFiles, Succeeded, Info0, Info) -->
	maybe_make_target_message(TargetFile),
	{ TargetFile = ModuleName - _FileType },
	{ CompilationTask = Task - TaskOptions },
	{ Cleanup =
		(pred(MakeInfo0::in, MakeInfo::out, di, uo) is det -->
			% XXX Remove `.int.tmp' files.
			list__foldl2(remove_target_file, TouchedTargetFiles,
				MakeInfo0, MakeInfo1),
			list__foldl2(remove_file, TouchedFiles,
				MakeInfo1, MakeInfo)
		) },
	build_with_check_for_interrupt(
	    build_with_module_options_and_output_redirect(ModuleName,
		TaskOptions, build_target_2(ModuleName, Task, Imports)),
	    Cleanup, Succeeded, Info0, Info1),
    	record_made_target_2(Succeeded, TargetFile, TouchedTargetFiles,
	    TouchedFiles, Info1, Info).

:- pred build_target_2(module_name::in, compilation_task_type::in,
	module_imports::in, list(string)::in, io__output_stream::in,
	bool::out, make_info::in, make_info::out,
	io__state::di, io__state::uo) is det.

build_target_2(ModuleName, process_module(ModuleTask), _Imports,
		AllOptionArgs, ErrorStream, Succeeded, Info, Info) -->
	{ prog_out__sym_name_to_string(ModuleName, ".", ModuleArg) },

	globals__io_lookup_bool_option(verbose_commands, Verbose),
	( { Verbose = yes } ->
		{ AllArgs = list__append(AllOptionArgs, [ModuleArg]) },
		io__write_string("Invoking command `mmc "),
		% XXX Don't write the default options.
		io__write_list(quote_args(AllArgs), " ",
			io__write_string),
		io__write_string("'"),
		io__nl
	;
		[]
	),

	%
	% Run compilations to target code in a separate process.
	% This is necessary for `--target asm' because the GCC
	% backend can only be invoked once per process. It's a good
	% idea for other the backends because it avoids problems with
	% the Boehm GC retaining memory by scanning too much of the
	% Mercury stacks. If the compilation is run in a separate
	% process, it is also easier to kill if an interrupt arrives.
	%
	io__set_output_stream(ErrorStream, OldOutputStream),
	( { ModuleTask = compile_to_target_code } ->
		call_in_forked_process(call_mercury_compile_main([ModuleArg]),
			invoke_mmc(ErrorStream, AllOptionArgs), Succeeded)
	;
		call_mercury_compile_main([ModuleArg], Succeeded)
	),
	io__set_output_stream(OldOutputStream, _),

	(
		{ ModuleTask = compile_to_target_code
		; ModuleTask = errorcheck
		}
	->
		% The `.err_date' file is needed because the `.err'
		% file is touched by all phases of compilation, including
		% writing interfaces.
		touch_interface_datestamp(ModuleName, ".err_date")
	;
		[]
	).

build_target_2(ModuleName, target_code_to_object_code(PIC),
		Imports, _, ErrorStream, Succeeded, Info0, Info) -->
	get_target_code_to_object_code_foreign_files(ModuleName,
		ForeignCodeFiles, Info0, Info),
	globals__io_get_target(CompilationTarget),

	{ CompileTargetCode =
	    (pred(Succeeded1::out, di, uo) is det -->
		build_object_code(ModuleName, CompilationTarget, PIC,
			ErrorStream, Imports, Succeeded0),
		list__map_foldl(compile_foreign_code_file(ErrorStream, PIC),
			ForeignCodeFiles, ForeignCodeSucceeded),
		{
			Succeeded0 = yes,
			\+ list__member(no, ForeignCodeSucceeded)
		->
			Succeeded1 = yes
		;
			Succeeded1 = no
		}
	    ) },


	% Run the compilation in a child process so it can
	% be killed if an interrupt arrives.
	call_in_forked_process(CompileTargetCode,
		CompileTargetCode, Succeeded).

:- pred build_object_code(module_name::in, compilation_target::in, pic::in,
	io__output_stream::in, module_imports::in, bool::out,
	io__state::di, io__state::uo) is det.

build_object_code(ModuleName, c, PIC, ErrorStream, _Imports, Succeeded) -->
	compile_target_code__compile_c_file(ErrorStream, PIC, ModuleName,
		Succeeded).
build_object_code(ModuleName, asm, PIC, ErrorStream, _Imports, Succeeded) -->
	compile_target_code__assemble(ErrorStream, PIC, ModuleName,
		Succeeded).
build_object_code(ModuleName, java, _, ErrorStream, _Imports, Succeeded) -->
	compile_target_code__compile_java_file(ErrorStream,
		ModuleName, Succeeded).
build_object_code(ModuleName, il, _, ErrorStream, Imports, Succeeded) -->
	compile_target_code__il_assemble(ErrorStream, ModuleName,
		Imports ^ has_main, Succeeded).

:- pred compile_foreign_code_file(io__output_stream::in, pic::in,
	foreign_code_file::in, bool::out, io__state::di, io__state::uo) is det.

compile_foreign_code_file(ErrorStream, PIC,
		foreign_code_file(c, CFile, ObjFile), Succeeded) -->
	compile_target_code__compile_c_file(ErrorStream, PIC,
		CFile, ObjFile, Succeeded).
compile_foreign_code_file(ErrorStream, _,
		foreign_code_file(il, ILFile, DLLFile), Succeeded) -->
	compile_target_code__il_assemble(ErrorStream, ILFile, DLLFile,
		no_main, Succeeded).
compile_foreign_code_file(ErrorStream, _,
		foreign_code_file(managed_cplusplus, MCPPFile, DLLFile),
		Succeeded) -->
	compile_target_code__compile_managed_cplusplus_file(ErrorStream,
		MCPPFile, DLLFile, Succeeded).
compile_foreign_code_file(ErrorStream, _,
		foreign_code_file(csharp, CSharpFile, DLLFile),
		Succeeded) -->
	compile_target_code__compile_csharp_file(ErrorStream,
		CSharpFile, DLLFile, Succeeded).

%-----------------------------------------------------------------------------%

:- pred call_mercury_compile_main(list(string)::in, bool::out,
		io__state::di, io__state::uo) is det.

call_mercury_compile_main(Args, Succeeded) -->
	io__get_exit_status(Status0),
	io__set_exit_status(0),
	mercury_compile__main(Args),
	io__get_exit_status(Status),
	{ Succeeded = ( Status = 0 -> yes ; no ) },
	io__set_exit_status(Status0).

:- pred invoke_mmc(io__output_stream::in, list(string)::in, bool::out,
		io__state::di, io__state::uo) is det.

invoke_mmc(ErrorStream, Args, Succeeded) -->
	{ CommandVerbosity = verbose }, % We've already written the command.
	{ Command = string__join_list(" ", ["mmc" | quote_args(Args)]) },
	invoke_shell_command(ErrorStream, CommandVerbosity,
		Command, Succeeded).

%-----------------------------------------------------------------------------%

record_made_target(TargetFile, CompilationTask, Succeeded, Info0, Info) -->
	touched_files(TargetFile, CompilationTask, TouchedTargetFiles,
		TouchedFiles, Info0, Info1),
	record_made_target_2(Succeeded, TargetFile, TouchedTargetFiles,
		TouchedFiles, Info1, Info).

:- pred record_made_target_2(bool::in, target_file::in, list(target_file)::in,
	list(file_name)::in, make_info::in, make_info::out,
	io__state::di, io__state::uo) is det.

record_made_target_2(Succeeded, TargetFile, TouchedTargetFiles,
		OtherTouchedFiles, Info0, Info) -->
	( { Succeeded = yes } ->
		{ TargetStatus = up_to_date },
		{ Info1 = Info0 }
	;
		{ TargetStatus = error },
		{ Info1 = Info0 },
		target_file_error(TargetFile)
	),

	{ list__foldl(update_target_status(TargetStatus),
	    TouchedTargetFiles, Info1, Info2) },

	{ DeleteTimestamp =
	    (pred(TouchedFile::in, MakeInfo0::in, MakeInfo::out) is det :-
		MakeInfo = MakeInfo0 ^ file_timestamps :=
			map__delete(MakeInfo0 ^ file_timestamps, TouchedFile)
	    ) },
	list__map_foldl2(get_file_name, TouchedTargetFiles,
		TouchedTargetFileNames, Info2, Info3),
	{ list__foldl(DeleteTimestamp, TouchedTargetFileNames, Info3, Info4) },
	{ list__foldl(DeleteTimestamp, OtherTouchedFiles, Info4, Info) }.

:- pred update_target_status(dependency_status::in, target_file::in,
		make_info::in, make_info::out) is det.

update_target_status(TargetStatus, TargetFile, Info,
	Info ^ dependency_status ^ elem(target(TargetFile)) := TargetStatus).

%-----------------------------------------------------------------------------%

:- type compilation_task_result == pair(compilation_task_type, list(string)).

:- func compilation_task(globals, module_target_type) =
		compilation_task_result.

compilation_task(_, source) = _ :- error("compilation_task").
compilation_task(_, errors) =
		process_module(errorcheck) - ["--errorcheck-only"].
compilation_task(_, unqualified_short_interface) =
		process_module(make_short_interface) -
				["--make-short-interface"].
compilation_task(Globals, short_interface) =
		compilation_task(Globals, long_interface).
compilation_task(_, long_interface) =
		process_module(make_interface) - ["--make-interface"].
compilation_task(_, private_interface) =
		process_module(make_private_interface) -
			["--make-private-interface"].
compilation_task(_, intermodule_interface) =
		process_module(make_optimization_interface) -
			["--make-optimization-interface"].
compilation_task(_, aditi_code) =
		process_module(compile_to_target_code) - ["--aditi-only"].
compilation_task(Globals, c_header(_)) = compilation_task(Globals, c_code).
compilation_task(_, c_code) = process_module(compile_to_target_code) -
					["--compile-to-c"].
compilation_task(_, il_code) = process_module(compile_to_target_code) -
					["--il-only"].
compilation_task(_, il_asm) = target_code_to_object_code(non_pic) - [].
compilation_task(_, java_code) = process_module(compile_to_target_code) -
					["--java-only"].
compilation_task(_, asm_code(PIC)) =
		process_module(compile_to_target_code) - 
			( PIC = pic -> ["--pic"] ; [] ).
compilation_task(Globals, object_code(PIC)) =
			target_code_to_object_code(PIC) - Flags :-
		globals__get_target(Globals, Target),
		( PIC = pic ->
			Flags = ( Target = asm -> ["--pic"] ; ["--pic-reg"] )
		;
			Flags = []
		).

	% Find the files which could be touched by a compilation task.
:- pred touched_files(target_file::in, compilation_task_type::in,
	list(target_file)::out, list(file_name)::out,
	make_info::in, make_info::out, io__state::di, io__state::uo) is det.

touched_files(TargetFile, process_module(Task), TouchedTargetFiles,
		TouchedFileNames, Info0, Info) -->
	{ TargetFile = ModuleName - FileType },
	get_module_dependencies(ModuleName, MaybeImports, Info0, Info1),
	{ MaybeImports = yes(Imports0) ->
		Imports = Imports0
	;
		% This error should have been caught earlier.
		% We shouldn't be attempting to build a target
		% if we couldn't find the dependencies for the
		% module.
		error("touched_files: no module dependencies")
	},

	{ NestedChildren = Imports ^ nested_children },
	{ SourceFileModuleNames = [ModuleName | NestedChildren] },

	list__map_foldl2(get_module_dependencies, NestedChildren,
		MaybeNestedImportsList, Info1, Info),
	{
	    list__map(
		(pred(yes(NestedModuleImports)::in,
	    			NestedModuleImports::out) is semidet),
		MaybeNestedImportsList, NestedImportsList)
	->
	    ModuleImportsList = [Imports | NestedImportsList]
	;
		% This error should have been caught earlier.
		% We shouldn't be attempting to build a target
		% if we couldn't find the dependencies for the
		% module or its nested sub-modules.
	    error("touched_files: no nested module dependencies")
	},

	globals__io_get_target(CompilationTarget),
	{ Task = compile_to_target_code, CompilationTarget = asm ->
		% For `--target asm' the code for the nested children
		% is placed in the `.s' file for the top-level module
		% in the source file.
		TargetModuleNames = [ModuleName]
	;
		TargetModuleNames = SourceFileModuleNames
	},

	%
	% Find out what header files are generated.
	%
	(
	    { Task = compile_to_target_code }
	->
	    list__map_foldl(external_foreign_code_files, ModuleImportsList,
			ForeignCodeFileList),
	    { ForeignCodeFiles = list__map(
	    		(func(ForeignFile) = ForeignFile ^ target_file),
			list__condense(ForeignCodeFileList)) },
	    (
		{ CompilationTarget = c },
		globals__io_lookup_bool_option(highlevel_code, HighLevelCode),
		( { HighLevelCode = yes } ->
		    %
		    % When compiling to high-level C, we always generate
		    % a header file.
		    %
		    { HeaderModuleNames = SourceFileModuleNames },
		    { HeaderTargets0 = make_target_list(HeaderModuleNames,
		    			c_header(mih)) }
		;
		    { HeaderTargets0 = [] }	
		)
	    ;
	        { CompilationTarget = asm },
		%
		% When compiling to assembler, we only generate
		% a header file if the module contains foreign code.
		%
		{ HeaderModuleNames =
		    list__filter_map(
			(func(MImports) = MImports ^ module_name is semidet :-
			    contains_foreign_code(_) = MImports ^ foreign_code
			), ModuleImportsList) },
		{ HeaderTargets0 = make_target_list(HeaderModuleNames,
					c_header(mih)) }
	    ;
	    	{ CompilationTarget = il },
		{ HeaderTargets0 = [] }
	    ;
	    	{ CompilationTarget = java },
		{ HeaderTargets0 = [] }
	    ),

	    { ( CompilationTarget = c ; CompilationTarget = asm ) ->
		    %
		    % We only generate a `.mh' file if the module contains
		    % `:- pragma export' declarations.
		    %
	    	PragmaExportModuleNames =
			list__filter_map(
			    (func(MImports) =
			    		MImports ^ module_name is semidet :-
				contains_foreign_export =
				    MImports ^ contains_foreign_export
			    ), ModuleImportsList),
	    	HeaderTargets =
			make_target_list(PragmaExportModuleNames, c_header(mh))
			++ HeaderTargets0
	    ;
		HeaderTargets = HeaderTargets0
	    },

	    { TouchedTargetFiles0 =
			make_target_list(TargetModuleNames, FileType) },
	    { TouchedTargetFiles = TouchedTargetFiles0 ++ HeaderTargets }
	;
	    { Task = make_interface }
	->
	    % Both long and short interface files are produced
	    % when making the interface.
    	    { ForeignCodeFiles = [] },
	    { TouchedTargetFiles =
		make_target_list(TargetModuleNames, long_interface)
		++ make_target_list(TargetModuleNames, short_interface) }
	;
    	    { ForeignCodeFiles = [] },
	    { TouchedTargetFiles =
			make_target_list(TargetModuleNames, FileType) }
	),

	globals__io_get_globals(Globals),
	list__foldl2(
	    (pred((TargetModuleName - TargetFileType)::in, TimestampFiles0::in,
			TimestampFiles1::out, di, uo) is det -->
		(
			{ TimestampExt =
				timestamp_extension(Globals, TargetFileType) }
		->
			module_name_to_file_name(TargetModuleName,
				TimestampExt, no, TimestampFile),
			{ TimestampFiles1 =
				[TimestampFile | TimestampFiles0] }
		;
			{ TimestampFiles1 = TimestampFiles0 }			
		)
	    ), TouchedTargetFiles, [], TimestampFileNames),
			
	{ TouchedFileNames = list__condense([ForeignCodeFiles,
					TimestampFileNames]) }.

touched_files(TargetFile, target_code_to_object_code(_),
		[TargetFile], ForeignObjectFiles, Info0, Info) -->
	{ TargetFile = ModuleName - _ },
	get_target_code_to_object_code_foreign_files(ModuleName,
		ForeignCodeFileList, Info0, Info),
	{ ForeignObjectFiles = list__map(
			(func(ForeignFile) = ForeignFile ^ object_file),
			ForeignCodeFileList) }.

:- pred get_target_code_to_object_code_foreign_files(module_name::in, 
		list(foreign_code_file)::out, make_info::in, make_info::out,
		io__state::di, io__state::uo) is det.

get_target_code_to_object_code_foreign_files(ModuleName, ForeignCodeFiles,
		Info0, Info) -->
	get_module_dependencies(ModuleName, MaybeImports, Info0, Info1),
	{ MaybeImports = yes(Imports0) ->
		Imports = Imports0
	;
		% This error should have been caught earlier.
		% We shouldn't be attempting to build a target
		% if we couldn't find the dependencies for the
		% module.
		error(
"get_target_code_to_object_code_foreign_files: no module dependencies")
	},

	%
	% For `--target asm' there is only one `.s' file per module
	% so we should compile the foreign code for 
	%
	globals__io_get_target(CompilationTarget),
	( { CompilationTarget = asm } ->
		{ NestedChildren = Imports ^ nested_children },

		list__map_foldl2(get_module_dependencies, NestedChildren,
			MaybeNestedImportsList, Info1, Info),
		{
		    list__map(
			(pred(yes(NestedModuleImports)::in,
					NestedModuleImports::out) is semidet),
			MaybeNestedImportsList, NestedImportsList)
		->
		    ModuleImportsList = [Imports | NestedImportsList]
		;
			% This error should have been caught earlier.
			% We shouldn't be attempting to build a target
			% if we couldn't find the dependencies for the
			% module or its nested sub-modules.
		    error(
"get_target_code_to_object_code_foreign_files: no nested module dependencies")
		}
	;
		{ Info = Info1 },
		{ ModuleImportsList = [Imports] }
	),
	list__map_foldl(external_foreign_code_files,
		ModuleImportsList, ForeignCodeFileLists),
	{ ForeignCodeFiles = list__condense(ForeignCodeFileLists) }.

external_foreign_code_files(Imports, ForeignFiles) -->
	%
	% Find externally compiled foreign code files for
	% `:- pragma foreign_proc' declarations.
	%
	globals__io_get_target(CompilationTarget),
	globals__io_lookup_string_option(object_file_extension, ObjExt),
	{ ModuleName = Imports ^ module_name },
	(
		{ CompilationTarget = asm },
		{ Imports ^ foreign_code = contains_foreign_code(Langs) },
		{ set__member(c, Langs) }
	->
		module_name_to_file_name(
			foreign_language_module_name(ModuleName, c), ".c",
			no, CCodeFileName),
		module_name_to_file_name(
			foreign_language_module_name(ModuleName, c), ObjExt,
			no, ObjFileName),
		{ ForeignFiles0 =
			[foreign_code_file(c, CCodeFileName, ObjFileName) ] }
	;
		{ CompilationTarget = il },
		{ Imports ^ foreign_code = contains_foreign_code(Langs) }
	->
		list__map_foldl(external_foreign_code_files_for_il(ModuleName),
			set__to_sorted_list(Langs), ForeignFilesList),
		{ list__condense(ForeignFilesList, ForeignFiles0) }
	;
		{ ForeignFiles0 = [] }
	),

	%
	% Find externally compiled foreign code files for fact tables.
	%
	( { CompilationTarget = c ; CompilationTarget = asm } ->
		list__map_foldl(
			(pred(FactTableFile::in, FactTableForeignFile::out,
					di, uo) is det -->
				fact_table_file_name(ModuleName, FactTableFile,
					".c", FactTableCFile),
				fact_table_file_name(ModuleName, FactTableFile,
					ObjExt, FactTableObjFile),
				{ FactTableForeignFile = foreign_code_file(c, 
					FactTableCFile, FactTableObjFile) }
			), Imports ^ fact_table_deps, FactTableForeignFiles),
		{ ForeignFiles = ForeignFiles0 ++ FactTableForeignFiles }
	;
		{ ForeignFiles = ForeignFiles0 }
	).

:- pred external_foreign_code_files_for_il(module_name::in,
	foreign_language::in, list(foreign_code_file)::out,
	io__state::di, io__state::uo) is det.

external_foreign_code_files_for_il(ModuleName, Language,
		ForeignFiles) -->
	(
		{ ForeignModuleName = foreign_language_module_name(ModuleName, 
					Language) },
		{ ForeignExt = foreign_language_file_extension(Language) }
	->
		module_name_to_file_name(ForeignModuleName, ForeignExt, no, 
			ForeignFileName),
		module_name_to_file_name(ForeignModuleName, ".dll", no, 
			ForeignDLLFileName),
		{ ForeignFiles = [foreign_code_file(Language, ForeignFileName,
					ForeignDLLFileName)] }
	;
		% No external file is generated for this foreign language.
		{ ForeignFiles = [] }
	).

%-----------------------------------------------------------------------------%