1 files changed, 136 insertions, 0 deletions
diff --git a/src/internal/buildcfg/cfg.go b/src/internal/buildcfg/cfg.go
new file mode 100644
index 0000000000..9fe7f211fb
--- /dev/null
+++ b/src/internal/buildcfg/cfg.go
@@ -0,0 +1,136 @@
+// Copyright 2021 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.
+
+// Package buildcfg provides access to the build configuration
+// described by the current environment. It is for use by build tools
+// such as cmd/go or cmd/compile and for setting up go/build's Default context.
+//
+// Note that it does NOT provide access to the build configuration used to
+// build the currently-running binary. For that, use runtime.GOOS etc
+// as well as internal/goexperiment.
+package buildcfg
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var (
+	defaultGOROOT string // set by linker
+
+	GOROOT   = envOr("GOROOT", defaultGOROOT)
+	GOARCH   = envOr("GOARCH", defaultGOARCH)
+	GOOS     = envOr("GOOS", defaultGOOS)
+	GO386    = envOr("GO386", defaultGO386)
+	GOARM    = goarm()
+	GOMIPS   = gomips()
+	GOMIPS64 = gomips64()
+	GOPPC64  = goppc64()
+	GOWASM   = gowasm()
+	GO_LDSO  = defaultGO_LDSO
+	Version  = version
+)
+
+// Error is one of the errors found (if any) in the build configuration.
+var Error error
+
+// Check exits the program with a fatal error if Error is non-nil.
+func Check() {
+	if Error != nil {
+		fmt.Fprintf(os.Stderr, "%s: %v\n", filepath.Base(os.Args[0]), Error)
+		os.Exit(2)
+	}
+}
+
+func envOr(key, value string) string {
+	if x := os.Getenv(key); x != "" {
+		return x
+	}
+	return value
+}
+
+func goarm() int {
+	def := defaultGOARM
+	if GOOS == "android" && GOARCH == "arm" {
+		// Android arm devices always support GOARM=7.
+		def = "7"
+	}
+	switch v := envOr("GOARM", def); v {
+	case "5":
+		return 5
+	case "6":
+		return 6
+	case "7":
+		return 7
+	}
+	Error = fmt.Errorf("invalid GOARM: must be 5, 6, 7")
+	return int(def[0] - '0')
+}
+
+func gomips() string {
+	switch v := envOr("GOMIPS", defaultGOMIPS); v {
+	case "hardfloat", "softfloat":
+		return v
+	}
+	Error = fmt.Errorf("invalid GOMIPS: must be hardfloat, softfloat")
+	return defaultGOMIPS
+}
+
+func gomips64() string {
+	switch v := envOr("GOMIPS64", defaultGOMIPS64); v {
+	case "hardfloat", "softfloat":
+		return v
+	}
+	Error = fmt.Errorf("invalid GOMIPS64: must be hardfloat, softfloat")
+	return defaultGOMIPS64
+}
+
+func goppc64() int {
+	switch v := envOr("GOPPC64", defaultGOPPC64); v {
+	case "power8":
+		return 8
+	case "power9":
+		return 9
+	}
+	Error = fmt.Errorf("invalid GOPPC64: must be power8, power9")
+	return int(defaultGOPPC64[len("power")] - '0')
+}
+
+type gowasmFeatures struct {
+	SignExt bool
+	SatConv bool
+}
+
+func (f gowasmFeatures) String() string {
+	var flags []string
+	if f.SatConv {
+		flags = append(flags, "satconv")
+	}
+	if f.SignExt {
+		flags = append(flags, "signext")
+	}
+	return strings.Join(flags, ",")
+}
+
+func gowasm() (f gowasmFeatures) {
+	for _, opt := range strings.Split(envOr("GOWASM", ""), ",") {
+		switch opt {
+		case "satconv":
+			f.SatConv = true
+		case "signext":
+			f.SignExt = true
+		case "":
+			// ignore
+		default:
+			Error = fmt.Errorf("invalid GOWASM: no such feature %q", opt)
+		}
+	}
+	return
+}
+
+func Getgoextlinkenabled() string {
+	return envOr("GO_EXTLINK_ENABLED", defaultGO_EXTLINK_ENABLED)
+}