Provide a way to 'tag' systems, and filter on those tags.

src/base/os.lua

@@ -668,3 +668,22 @@
 		end
 		return id
 	end
+
+
+--
+-- Get a set of tags for different 'platforms'
+--
+
+	function os.getSystemTags(name)
+		local tags =
+		{
+			["aix"]      = { "aix",     "posix" },
+			["bsd"]      = { "bsd",     "posix" },
+			["haiku"]    = { "haiku",   "posix" },
+			["linux"]    = { "linux",   "posix" },
+			["macosx"]   = { "macosx",  "darwin", "posix" },
+			["solaris"]  = { "solaris", "posix" },
+			["windows"]  = { "windows", "win32" },
+		}
+		return tags[name] or name
+	end

src/base/oven.lua

@@ -64,7 +64,7 @@
 		context.addFilter(self, "action", _ACTION)
 
 		self.system = self.system or p.action.current().targetos or os.target()
-		context.addFilter(self, "system", self.system)
+		context.addFilter(self, "system", os.getSystemTags(self.system))
 
 		-- Add command line options to the filtering options
 		local options = {}
@@ -205,7 +205,7 @@
 		-- values that might already in the context to override my defaults.
 
 		self.system = self.system or p.action.current().targetos or os.target()
-		context.addFilter(self, "system", self.system)
+		context.addFilter(self, "system", os.getSystemTags(self.system))
 		context.addFilter(self, "architecture", self.architecture)
 
 		-- The kind is a configuration level value, but if it has been set at the
@@ -580,7 +580,7 @@
 
 		-- allow the project script to override the default system
 		ctx.system = ctx.system or system
-		context.addFilter(ctx, "system", ctx.system)
+		context.addFilter(ctx, "system", os.getSystemTags(ctx.system))
 
 		-- allow the project script to override the default architecture
 		ctx.architecture = ctx.architecture or architecture

tests/oven/test_filtering.lua

@@ -107,3 +107,27 @@
 		prepare()
 		test.isequal({}, cfg.defines)
 	end
+
+--
+-- Test filtering on system.
+--
+
+	function suite.onFilterLinuxIsPosix()
+		system "linux"
+		filter { "system:posix" }
+			defines { "POSIX" }
+		filter { "system:not posix" }
+			defines { "NOTPOSIX" }
+		prepare()
+		test.isequal({ "POSIX" }, cfg.defines)
+	end
+
+	function suite.onFilterWindowsIsNotPosix()
+		system "windows"
+		filter { "system:posix" }
+			defines { "POSIX" }
+		filter { "system:not posix" }
+			defines { "NOTPOSIX" }
+		prepare()
+		test.isequal({ "NOTPOSIX" }, cfg.defines)
+	end