gmake_cpp.lua

--
-- gmake_cpp.lua
-- Generate a C/C++ project makefile.
-- (c) 2016-2025 Jess Perkins, Blizzard Entertainment and the Premake project
--

	local p = premake
	local gmake = p.modules.gmake

	gmake.cpp       = {}
	local cpp        = gmake.cpp

	local project    = p.project
	local config     = p.config
	local fileconfig = p.fileconfig


---
-- Add namespace for element definition lists for premake.callarray()
---

	cpp.elements = {}


--
-- Generate a GNU make C++ project makefile, with support for the new platforms API.
--

	cpp.elements.makefile = function(prj)
		return {
			gmake.header,
			gmake.phonyRules,
			gmake.shellType,
			cpp.createRuleTable,
			cpp.outputConfigurationSection,
			cpp.outputPerFileConfigurationSection,
			cpp.createFileTable,
			cpp.outputFilesSection,
			cpp.outputRulesSection,
			cpp.outputFileRuleSection,
			cpp.dependencies,
		}
	end


	function cpp.generate(prj)
		p.eol("\n")
		p.callArray(cpp.elements.makefile, prj)

		-- allow the garbage collector to clean things up.
		for cfg in project.eachconfig(prj) do
			cfg._gmake = nil
		end
		prj._gmake = nil
	end


	function cpp.initialize()
		rule 'cpp'
			fileExtension { ".cc", ".cpp", ".cxx", ".mm" }
			buildoutputs  { "$(OBJDIR)/%{file.objname}%{premake.modules.gmake.cpp.gettooloutputext('cxx', cfg)}" }
			buildmessage  '$(notdir $<)'
			buildcommands {'$(CXX) %{premake.modules.gmake.cpp.fileFlags(cfg, file)} $(FORCE_INCLUDE) %{premake.modules.gmake.cpp.toolFlags(cfg, "cxx")}'}

		rule 'cc'
			fileExtension {".c", ".s", ".m"}
			buildoutputs  { "$(OBJDIR)/%{file.objname}%{premake.modules.gmake.cpp.gettooloutputext('cc', cfg)}" }
			buildmessage  '$(notdir $<)'
			buildcommands {'$(CC) %{premake.modules.gmake.cpp.fileFlags(cfg, file)} $(FORCE_INCLUDE) %{premake.modules.gmake.cpp.toolFlags(cfg, "cc")}'}

		rule 'resource'
			fileExtension ".rc"
			buildoutputs  { "$(OBJDIR)/%{file.objname}%{premake.modules.gmake.cpp.gettooloutputext('rc', cfg)}" }
			buildmessage  '$(notdir $<)'
			buildcommands {'$(RESCOMP) $(ALL_RESFLAGS) %{premake.modules.gmake.cpp.toolFlags(cfg, "rc")}'}

		global(nil)
	end

	function cpp.gettooloutputext(tool, cfg)
		local toolset = gmake.getToolSet(cfg)
		if toolset.gettooloutputext ~= nil then
			return toolset.gettooloutputext(tool)
		end

		return iif(tool == "rc", ".res", ".o")
	end

	function cpp.toolFlags(cfg, tool)
		local toolset = gmake.getToolSet(cfg)
		if toolset.gettoolflags ~= nil then
			return toolset.gettoolflags(cfg, tool, '"$<"', '"$@"', '"$(@:%.o=%.d)"')
		end

		if tool == "rc" then
			return '"$<" -O coff -o "$@"'
		else
			return '-o "$@" -MF "$(@:%.o=%.d)" -c "$<"'
		end
	end

	function cpp.createRuleTable(prj)
		local rules = {}

		local function addRule(extension, rule)
			if type(extension) == 'table' then
				for _, value in ipairs(extension) do
					addRule(value, rule)
				end
			else
				rules[extension] = rule
			end
		end

		-- add all rules.
		local usedRules = table.join({'cpp', 'cc', 'resource'}, prj.rules)
		for _, name in ipairs(usedRules) do
			local rule = p.global.getRule(name)
			addRule(rule.fileExtension, rule)
		end

		-- create fileset categories.
		local filesets = {
			['.o']   = 'OBJECTS',
			['.obj'] = 'OBJECTS',
			['.cc']  = 'SOURCES',
			['.cpp'] = 'SOURCES',
			['.cxx'] = 'SOURCES',
			['.mm']  = 'SOURCES',
			['.c']   = 'SOURCES',
			['.s']   = 'SOURCES',
			['.m']   = 'SOURCES',
			['.res'] = 'RESOURCES',
		}

		-- cache the result.
		prj._gmake = prj._gmake or {}
		prj._gmake.rules = rules
		prj._gmake.filesets = filesets
	end


	function cpp.createFileTable(prj)
		for cfg in project.eachconfig(prj) do
			cfg._gmake = cfg._gmake or {}
			cfg._gmake.filesets = {}
			cfg._gmake.fileRules = {}

			local files = table.shallowcopy(prj._.files)
			table.foreachi(files, function(node)
				cpp.addFile(cfg, node)
			end)

			for _, f in pairs(cfg._gmake.filesets) do
				table.sort(f)
			end

			cfg._gmake.kinds = table.keys(cfg._gmake.filesets)
			table.sort(cfg._gmake.kinds)

			prj._gmake.kinds = table.join(prj._gmake.kinds or {}, cfg._gmake.kinds)
		end

		-- we need to reassign object sequences if we generated any files.
		if prj.hasGeneratedFiles and p.project.iscpp(prj) then
			p.oven.assignObjectSequences(prj)
		end

		prj._gmake.kinds = table.unique(prj._gmake.kinds)
		table.sort(prj._gmake.kinds)
	end


	function cpp.addFile(cfg, node)
		local filecfg = fileconfig.getconfig(node, cfg)
		if not filecfg or filecfg.buildaction == "None" or filecfg.excludefrombuild then
			return
		end

		-- skip generated files, since we try to figure it out manually below.
		if node.generated then
			return
		end

		-- process custom build commands.
		if fileconfig.hasCustomBuildRule(filecfg) then
			local env = table.shallowcopy(filecfg.environ)
			local shadowContext = p.context.extent(filecfg, env)

			local buildoutputs = p.project.getrelative(cfg.project, shadowContext.buildoutputs)
			if buildoutputs and #buildoutputs > 0 then
				local file = {
					buildoutputs  = buildoutputs,
					source        = node.relpath,
					buildmessage  = shadowContext.buildmessage,
					buildcommands = shadowContext.buildcommands,
					buildinputs   = p.project.getrelative(cfg.project, shadowContext.buildinputs)
				}
				table.insert(cfg._gmake.fileRules, file)

				for _, output in ipairs(buildoutputs) do
					cpp.addGeneratedFile(cfg, node, output)
				end
			end
		elseif filecfg.buildaction == "Copy" then
			local output = '$(TARGETDIR)/' .. node.name
			local file = {
				buildoutputs  = { output },
				source        = node.relpath,
				buildmessage  = '$(notdir $<)',
				verbatimbuildcommands = gmake.copyfile_cmds('"$<"', '"$@"'),
				buildinputs = {'$(TARGETDIR)'}
			}
			table.insert(cfg._gmake.fileRules, file)
			cpp.addGeneratedFile(cfg, node, output)
		else
			cpp.addRuleFile(cfg, node)
		end
	end

	function cpp.determineFiletype(cfg, node)
		-- determine which filetype to use
		local filecfg = fileconfig.getconfig(node, cfg)
		local fileext = path.getextension(node.abspath):lower()
		if filecfg and filecfg.compileas then
			if p.languages.isc(filecfg.compileas) then
				fileext = ".c"
			elseif p.languages.iscpp(filecfg.compileas) then
				fileext = ".cpp"
			end
		end

		return fileext;
	end

	function cpp.addGeneratedFile(cfg, source, filename)
		-- mark that we have generated files.
		cfg.project.hasGeneratedFiles = true

		-- add generated file to the project.
		local files = cfg.project._.files
		local node = files[filename]
		if not node then
			node = fileconfig.new(filename, cfg.project)
			files[filename] = node
			table.insert(files, node)
		end

		-- always overwrite the dependency information.
		node.dependsOn = source
		node.generated = true

		-- add to config if not already added.
		if not fileconfig.getconfig(node, cfg) then
			fileconfig.addconfig(node, cfg)
		end

		-- determine which filetype to use
		local fileext = cpp.determineFiletype(cfg, node)
		-- add file to the fileset.
		local filesets = cfg.project._gmake.filesets
		local kind     = filesets[fileext] or "CUSTOM"

		-- don't link generated object files automatically if it's explicitly
		-- disabled.
		if path.isobjectfile(filename) and source.linkbuildoutputs == false then
			kind = "CUSTOM"
		end

		local fileset = cfg._gmake.filesets[kind] or {}
		table.insert(fileset, filename)
		cfg._gmake.filesets[kind] = fileset

		local generatedKind = "GENERATED"
		local generatedFileset = cfg._gmake.filesets[generatedKind] or {}
		table.insert(generatedFileset, filename)
		cfg._gmake.filesets[generatedKind] = generatedFileset

		-- recursively setup rules.
		cpp.addRuleFile(cfg, node)
	end

	function cpp.addRuleFile(cfg, node)
		local rules = cfg.project._gmake.rules
		local fileext = cpp.determineFiletype(cfg, node)
		local rule = rules[fileext]
		if rule then

			local filecfg = fileconfig.getconfig(node, cfg)
			local environ = table.shallowcopy(filecfg.environ)

			if rule.propertydefinition then
				p.rule.prepareEnvironment(rule, environ, cfg)
				p.rule.prepareEnvironment(rule, environ, filecfg)
			end

			local shadowContext = p.context.extent(rule, environ)

			local buildoutputs  = shadowContext.buildoutputs
			local buildmessage  = shadowContext.buildmessage
			local buildcommands = shadowContext.buildcommands
			local buildinputs   = shadowContext.buildinputs

			buildoutputs = p.project.getrelative(cfg.project, buildoutputs)
			if buildoutputs and #buildoutputs > 0 then
				local file = {
					buildoutputs  = buildoutputs,
					source        = node.relpath,
					buildmessage  = buildmessage,
					buildcommands = buildcommands,
					buildinputs   = buildinputs
				}
				table.insert(cfg._gmake.fileRules, file)

				for _, output in ipairs(buildoutputs) do
					cpp.addGeneratedFile(cfg, node, output)
				end
			end
		end
	end


--
-- Write out the settings for a particular configuration.
--

	cpp.elements.configuration = function(cfg)
		return {
			cpp.tools,
			gmake.target,
			gmake.objdir,
			cpp.pch,
			cpp.defines,
			cpp.includes,
			cpp.forceInclude,
			cpp.cppFlags,
			cpp.cFlags,
			cpp.cxxFlags,
			cpp.resFlags,
			cpp.libs,
			cpp.ldDeps,
			cpp.ldFlags,
			cpp.linkCmd,
			cpp.bindirs,
			cpp.exepaths,
			gmake.settings,
			gmake.preBuildCmds,
			gmake.preLinkCmds,
			gmake.postBuildCmds,
		}
	end


	function cpp.outputConfigurationSection(prj)
		_p('# Configurations')
		_p('# #############################################')
		_p('')
		gmake.outputSection(prj, cpp.elements.configuration)
	end


	function cpp.tools(cfg, toolset)
		local tool = toolset.gettoolname(cfg, "cc")
		if tool then
			_p('ifeq ($(origin CC), default)')
			_p('  CC = %s', tool)
			_p('endif' )
		end

		tool = toolset.gettoolname(cfg, "cxx")
		if tool then
			_p('ifeq ($(origin CXX), default)')
			_p('  CXX = %s', tool)
			_p('endif' )
		end

		tool = toolset.gettoolname(cfg, "ar")
		if tool then
			_p('ifeq ($(origin AR), default)')
			_p('  AR = %s', tool)
			_p('endif' )
		end

		tool = toolset.gettoolname(cfg, "rc")
		if tool then
			_p('RESCOMP = %s', tool)
		end
	end


	function cpp.pch(cfg, toolset)
		local getpch = toolset.getpch or p.tools.gcc.getpch
		local pch = getpch(cfg)
		-- If there is no header, or if PCH has been disabled, I can early out
		if pch == nil then
			return
		end

		p.outln('PCH = ' .. pch)
		p.outln('PCH_PLACEHOLDER = $(OBJDIR)/$(notdir $(PCH))')
		p.outln('GCH = $(PCH_PLACEHOLDER).gch')
	end


	function cpp.defines(cfg, toolset)
		p.outln('DEFINES +=' .. gmake.list(table.join(toolset.getdefines(cfg.defines, cfg), toolset.getundefines(cfg.undefines))))
	end


	function cpp.includes(cfg, toolset)
		local includes = toolset.getincludedirs(cfg, cfg.includedirs, cfg.externalincludedirs, cfg.frameworkdirs, cfg.includedirsafter)
		p.outln('INCLUDES +=' .. gmake.list(includes))
	end


	function cpp.forceInclude(cfg, toolset)
		local includes = toolset.getforceincludes(cfg)
		p.outln('FORCE_INCLUDE +=' .. gmake.list(includes))
	end


	function cpp.cppFlags(cfg, toolset)
		local flags = gmake.list(toolset.getcppflags(cfg))
		p.outln('ALL_CPPFLAGS += $(CPPFLAGS)' .. flags .. ' $(DEFINES) $(INCLUDES)')
	end


	function cpp.cFlags(cfg, toolset)
		local flags = gmake.list(table.join(toolset.getcflags(cfg), cfg.buildoptions))
		p.outln('ALL_CFLAGS += $(CFLAGS) $(ALL_CPPFLAGS)' .. flags)
	end


	function cpp.cxxFlags(cfg, toolset)
		local flags = gmake.list(table.join(toolset.getcxxflags(cfg), cfg.buildoptions))
		p.outln('ALL_CXXFLAGS += $(CXXFLAGS) $(ALL_CPPFLAGS)' .. flags)
	end


	function cpp.resFlags(cfg, toolset)
		local resflags = table.join(toolset.getdefines(cfg.resdefines), toolset.getincludedirs(cfg, cfg.resincludedirs), cfg.resoptions)
		p.outln('ALL_RESFLAGS += $(RESFLAGS) $(DEFINES) $(INCLUDES)' .. gmake.list(resflags))
	end


	function cpp.libs(cfg, toolset)
		local flags = toolset.getlinks(cfg)
		p.outln('LIBS +=' .. gmake.list(flags, true))
	end


	function cpp.ldDeps(cfg, toolset)
		local deps = config.getlinks(cfg, "siblings", "fullpath")
		p.outln('LDDEPS +=' .. gmake.list(p.esc(deps)))
	end


	function cpp.ldFlags(cfg, toolset)
		local flags = table.join(toolset.getLibraryDirectories(cfg), toolset.getrunpathdirs(cfg, table.join(cfg.runpathdirs, config.getsiblingtargetdirs(cfg))), toolset.getSections(cfg), toolset.getldflags(cfg), cfg.linkoptions)
		p.outln('ALL_LDFLAGS += $(LDFLAGS)' .. gmake.list(flags))
	end


	function cpp.linkCmd(cfg, toolset)
		if cfg.kind == p.UTILITY then
			-- Empty LINKCMD for Utility (only custom build rules)
			p.outln('LINKCMD =')
			return
		end

		local linker = iif(cfg.kind == p.STATICLIB, "$(AR)", iif(p.languages.isc(cfg.language), "$(CC)", "$(CXX)"))

		if toolset.getlinkcommand ~= nil then
			p.outln('LINKCMD = ' .. toolset.getlinkcommand(cfg, linker, '"$@"', '$(OBJECTS)', '$(RESOURCES)', '$(ALL_LDFLAGS)', '$(LIBS)'))
			return
		end

		-- Fallback to previous version
		if cfg.kind == p.STATICLIB then
			if cfg.architecture == p.UNIVERSAL then
				p.outln('LINKCMD = libtool -o "$@" $(OBJECTS)')
			else
				p.outln('LINKCMD = ' .. linker .. ' -rcs "$@" $(OBJECTS)')
			end
		else
			-- this was $(TARGET) $(LDFLAGS) $(OBJECTS)
			--   but had trouble linking to certain static libs; $(OBJECTS) moved up
			-- $(LDFLAGS) moved to end (http://sourceforge.net/p/premake/patches/107/)
			-- $(LIBS) moved to end (http://sourceforge.net/p/premake/bugs/279/)
			p.outln('LINKCMD = ' .. linker .. ' -o "$@" $(OBJECTS) $(RESOURCES) $(ALL_LDFLAGS) $(LIBS)')
		end
	end


	function cpp.bindirs(cfg, toolset)
		local dirs = project.getrelative(cfg.project, cfg.bindirs)
		if #dirs > 0 then
			p.outln('EXECUTABLE_PATHS = "' .. table.concat(dirs, ":") .. '"')
		end
	end


	function cpp.exepaths(cfg, toolset)
		local dirs = project.getrelative(cfg.project, cfg.bindirs)
		if #dirs > 0 then
			p.outln('EXE_PATHS = export PATH=$(EXECUTABLE_PATHS):$$PATH;')
		end
	end


--
-- Write out the per file configurations.
--
	function cpp.outputPerFileConfigurationSection(prj)
		_p('# Per File Configurations')
		_p('# #############################################')
		_p('')
		for cfg in project.eachconfig(prj) do
			table.foreachi(prj._.files, function(node)
				local fcfg = fileconfig.getconfig(node, cfg)
				if fcfg then
					cpp.perFileFlags(cfg, fcfg)
				end
			end)
		end
		_p('')
	end

	function cpp.makeVarName(prj, value, saltValue)
		prj._gmake = prj._gmake or {}
		prj._gmake.varlist = prj._gmake.varlist or {}
		prj._gmake.varlistlength = prj._gmake.varlistlength or 0
		local cache = prj._gmake.varlist
		local length = prj._gmake.varlistlength

		local key = value .. saltValue

		if (cache[key] ~= nil) then
			return cache[key], false
		end

		local var = string.format("PERFILE_FLAGS_%d", length)
		cache[key] = var

		prj._gmake.varlistlength = length + 1

		return var, true
	end

	function cpp.perFileFlags(cfg, fcfg)
		local toolset = gmake.getToolSet(cfg)

		local isCFile = path.iscfile(fcfg.name)

		local getflags = iif(isCFile, toolset.getcflags, toolset.getcxxflags)
		local value = gmake.list(table.join(getflags(fcfg), fcfg.buildoptions))

		if fcfg.defines or fcfg.undefines then
			local defs = table.join(toolset.getdefines(fcfg.defines, cfg), toolset.getundefines(fcfg.undefines))
			if #defs > 0 then
				value = value .. gmake.list(defs)
			end
		end

		if fcfg.includedirs or fcfg.externalincludedirs or fcfg.frameworkdirs then
			local includes = toolset.getincludedirs(cfg, fcfg.includedirs, fcfg.externalincludedirs, fcfg.frameworkdirs)
			if #includes > 0 then
				value = value ..  gmake.list(includes)
			end
		end

		if #value > 0 then
			local newPerFileFlag = false
			fcfg.flagsVariable, newPerFileFlag = cpp.makeVarName(cfg.project, value, iif(isCFile, '_C', '_CPP'))
			if newPerFileFlag then
				if isCFile then
					_p('%s = $(ALL_CFLAGS)%s', fcfg.flagsVariable, value)
				else
					_p('%s = $(ALL_CXXFLAGS)%s', fcfg.flagsVariable, value)
				end
			end
		end
	end

	function cpp.fileFlags(cfg, file)
		local fcfg = fileconfig.getconfig(file, cfg)
		local flags = {}

		local toolset = gmake.getToolSet(cfg)
		local getpch = toolset.getpch or p.tools.gcc.getpch
		if getpch(cfg) and cfg.pchheader and cfg.enablepch ~= p.OFF and (not fcfg or fcfg.enablepch ~= p.OFF) then
			table.insert(flags, "-include $(PCH_PLACEHOLDER)")
		end

		if fcfg and fcfg.flagsVariable then
			table.insert(flags, string.format("$(%s)", fcfg.flagsVariable))
		else
			local fileExt = cpp.determineFiletype(cfg, file)

			if path.iscfile(fileExt) then
				table.insert(flags, "$(ALL_CFLAGS)")
			elseif path.iscppfile(fileExt) then
				table.insert(flags, "$(ALL_CXXFLAGS)")
			end
		end

		return table.concat(flags, ' ')
	end

--
-- Write out the file sets.
--

	cpp.elements.filesets = function(cfg)
		local result = {}
		for _, kind in ipairs(cfg._gmake.kinds) do
			for _, f in ipairs(cfg._gmake.filesets[kind]) do
				table.insert(result, function(cfg, toolset)
					cpp.outputFileset(cfg, kind, f)
				end)
			end
		end
		return result
	end

	function cpp.outputFilesSection(prj)
		_p('# File sets')
		_p('# #############################################')
		_p('')

		for _, kind in ipairs(prj._gmake.kinds) do
			_x('%s :=', kind)
		end
		_x('')

		gmake.outputSection(prj, cpp.elements.filesets)
	end

	function cpp.outputFileset(cfg, kind, file)
		_x('%s += %s', kind, file)
	end


--
-- Write out the targets.
--

	cpp.elements.rules = function(cfg)
		return {
			cpp.allRules,
			cpp.targetRules,
			gmake.targetDirRules,
			gmake.objDirRules,
			cpp.cleanRules,
			gmake.preBuildRules,
			cpp.customDeps,
			cpp.pchRules,
		}
	end


	function cpp.outputRulesSection(prj)
		_p('# Rules')
		_p('# #############################################')
		_p('')
		gmake.outputSection(prj, cpp.elements.rules)
	end


	function cpp.allRules(cfg, toolset)
		if cfg.system == p.MACOSX and cfg.kind == p.WINDOWEDAPP then
			_p('all: $(TARGET) $(dir $(TARGETDIR))PkgInfo $(dir $(TARGETDIR))Info.plist')
			_p('\t@:')
			_p('')
			_p('$(dir $(TARGETDIR))PkgInfo:')
			_p('$(dir $(TARGETDIR))Info.plist:')
		else
			_p('all: $(TARGET)')
			_p('\t@:')
		end
		_p('')
	end


	function cpp.targetRules(cfg, toolset)
		local targets = ''

		for _, kind in ipairs(cfg._gmake.kinds) do
			if kind ~= 'OBJECTS' and kind ~= 'RESOURCES' then
				targets = targets .. '$(' .. kind .. ') '
			end
		end

		targets = targets .. '$(OBJECTS) $(LDDEPS)'
		if cfg._gmake.filesets['RESOURCES'] then
			targets = targets .. ' $(RESOURCES)'
		end

		_p('$(TARGET): %s | $(TARGETDIR)', targets)
		_p('\t$(PRELINKCMDS)')
		_p('\t@echo Linking %s', cfg.project.name)
		_p('\t$(SILENT) $(LINKCMD)')
		_p('\t$(POSTBUILDCMDS)')
		_p('')
	end


	function cpp.customDeps(cfg, toolset)
		for _, kind in ipairs(cfg._gmake.kinds) do
			if kind == 'CUSTOM' or kind == 'SOURCES' then
				_p('$(%s): | prebuild', kind)
			end
		end
	end


	function cpp.cleanRules(cfg, toolset)
		_p('clean:')
		_p('\t@echo Cleaning %s', cfg.project.name)
		_p('ifeq (posix,$(SHELLTYPE))')
		_p('\t$(SILENT) rm -f  $(TARGET)')
		_p('\t$(SILENT) rm -rf $(GENERATED)')
		_p('\t$(SILENT) rm -rf $(OBJDIR)')
		_p('else')
		_p('\t$(SILENT) if exist $(subst /,\\\\,$(TARGET)) del $(subst /,\\\\,$(TARGET))')
		_p('\t$(SILENT) $(foreach f,$(subst /,\\\\,$(GENERATED)),if exist $(f) del /s /q $(f) >nul &)')
		_p('\t$(SILENT) if exist $(subst /,\\\\,$(OBJDIR)) rmdir /s /q $(subst /,\\\\,$(OBJDIR))')
		_p('endif')
		_p('')
	end


	function cpp.pchRules(cfg, toolset)
		_p('ifneq (,$(PCH))')
		_p('$(OBJECTS): $(GCH) | $(PCH_PLACEHOLDER)')
		_p('$(GCH): $(PCH) | prebuild')
		_p('\t@echo $(notdir $<)')
		local cmd = iif(p.languages.isc(cfg.language), "$(CC) -x c-header $(ALL_CFLAGS)", "$(CXX) -x c++-header $(ALL_CXXFLAGS)")
		_p('\t$(SILENT) %s -o "$@" -MF "$(@:%%.gch=%%.d)" -c "$<"', cmd)
		_p('$(PCH_PLACEHOLDER): $(GCH) | $(OBJDIR)')
		_p('ifeq (posix,$(SHELLTYPE))')
		_p('\t$(SILENT) touch "$@"')
		_p('else')
		_p('\t$(SILENT) echo $null >> "$@"')
		_p('endif')
		_p('else')
		_p('$(OBJECTS): | prebuild')
		_p('endif')
		_p('')
	end

--
-- Output the file compile targets.
--

	cpp.elements.fileRules = function(cfg)
		local funcs = {}
		for _, fileRule in ipairs(cfg._gmake.fileRules) do
			table.insert(funcs, function(cfg, toolset)
				cpp.outputFileRules(cfg, fileRule)
			end)
		end
		return funcs
	end


	function cpp.outputFileRuleSection(prj)
		_p('# File Rules')
		_p('# #############################################')
		_p('')
		gmake.outputSection(prj, cpp.elements.fileRules)
	end


	function cpp.outputFileRules(cfg, file)
		local dependencies = p.esc(file.source)
		if file.buildinputs and #file.buildinputs > 0 then
			dependencies = dependencies .. " " .. table.concat(p.esc(file.buildinputs), " ")
		end

		_p('%s: %s', file.buildoutputs[1], dependencies)

		if file.buildmessage then
			_p('\t@echo %s', p.quote(file.buildmessage))
		end

		if file.buildcommands then
			local cmds = os.translateCommandsAndPaths(file.buildcommands, cfg.project.basedir, cfg.project.location)
			for _, cmd in ipairs(cmds) do
				if cfg.bindirs and #cfg.bindirs > 0 then
					_p('\t$(SILENT) $(EXE_PATHS) %s', cmd)
				else
					_p('\t$(SILENT) %s', cmd)
				end
			end
		end
		if file.verbatimbuildcommands then
			for _, cmd in ipairs(file.verbatimbuildcommands) do
				_p('%s', cmd);
			end
		end
		-- TODO: this is a hack with some imperfect side-effects.
		--       better solution would be to emit a dummy file for the rule, and then outputs depend on it (must clean up dummy in 'clean')
		--       better yet, is to use pattern rules, but we need to detect that all outputs have the same stem
		if #file.buildoutputs > 1 then
			_p('%s: %s', table.concat({ table.unpack(file.buildoutputs, 2) }, ' '), file.buildoutputs[1])
		end
	end


---------------------------------------------------------------------------
--
-- Handlers for individual makefile elements
--
---------------------------------------------------------------------------


	-- Returns true if the configuration's toolset produces GNU make dependency files
	function cpp.usesDependencyFiles(cfg)
		return gmake.getToolSet(cfg) ~= p.tools.msc
	end

	function cpp.dependencies(prj)
		local function emitInclude()
			_p('-include $(OBJECTS:%%.o=%%.d)')
			_p('ifneq (,$(PCH))')
				_p('  -include $(PCH_PLACEHOLDER).d')
			_p('endif')
		end

		local depConfigs = {}
		local total = 0
		for cfg in project.eachconfig(prj) do
			total = total + 1
			if cpp.usesDependencyFiles(cfg) then
				table.insert(depConfigs, cfg.shortname)
			end
		end

		if #depConfigs == 0 then
			-- No configuration produces dependency files, emit nothing.
			return
		elseif #depConfigs == total then
			-- Every configuration produces dependency files, no guard needed.
			emitInclude()
		else
			-- Mixed toolsets, so only include for the configs that produce dependency files.
			_x('ifneq (,$(filter $(config),%s))', table.concat(depConfigs, ' '))
			emitInclude()
			_p('endif')
		end
	end