Add runtime warnings

constant/goos/gengoos.go

@@ -0,0 +1,68 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var gooses []string
+
+func main() {
+	data, err := os.ReadFile("../../go/build/syslist.go")
+	if err != nil {
+		log.Fatal(err)
+	}
+	const goosPrefix = `const goosList = `
+	for _, line := range strings.Split(string(data), "\n") {
+		if strings.HasPrefix(line, goosPrefix) {
+			text, err := strconv.Unquote(strings.TrimPrefix(line, goosPrefix))
+			if err != nil {
+				log.Fatalf("parsing goosList: %v", err)
+			}
+			gooses = strings.Fields(text)
+		}
+	}
+
+	for _, target := range gooses {
+		if target == "nacl" {
+			continue
+		}
+		var tags []string
+		if target == "linux" {
+			tags = append(tags, "!android") // must explicitly exclude android for linux
+		}
+		if target == "solaris" {
+			tags = append(tags, "!illumos") // must explicitly exclude illumos for solaris
+		}
+		if target == "darwin" {
+			tags = append(tags, "!ios") // must explicitly exclude ios for darwin
+		}
+		tags = append(tags, target) // must explicitly include target for bootstrapping purposes
+		var buf bytes.Buffer
+		fmt.Fprintf(&buf, "// Code generated by gengoos.go using 'go generate'. DO NOT EDIT.\n\n")
+		fmt.Fprintf(&buf, "//go:build %s\n", strings.Join(tags, " && "))
+		fmt.Fprintf(&buf, "package goos\n\n")
+		fmt.Fprintf(&buf, "const GOOS = `%s`\n\n", target)
+		for _, goos := range gooses {
+			value := 0
+			if goos == target {
+				value = 1
+			}
+			fmt.Fprintf(&buf, "const Is%s = %d\n", strings.Title(goos), value)
+		}
+		err := os.WriteFile("zgoos_"+target+".go", buf.Bytes(), 0o666)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+}