math can build, try to cgo-build goroot pkgs, added some more exceptions

gb/cgo.go

@@ -50,9 +50,11 @@ var TestCGO = true
 func BuildCgoPackage(pkg *Package) (err error) {
 	//defer fmt.Println(err)
 
-	if pkg.IsInGOROOT {
-		return MakeBuild(pkg)
-	}
+	/*
+		if pkg.IsInGOROOT {
+			return MakeBuild(pkg)
+		}
+	*/
 
 	if !TestCGO {
 		return MakeBuild(pkg)
@@ -109,15 +111,20 @@ func BuildCgoPackage(pkg *Package) (err error) {
 		err = Copy(pkg.Dir, cgosrc, cgd)
 		cgo_argv = append(cgo_argv, cgb)
 	}
-	if Verbose {
-		fmt.Printf("%s:", cgodir)
-	}
-	err = RunExternal(CGoCMD, cgodir, cgo_argv)
-	if err != nil {
-		return
+	if len(pkg.CGoSources) != 0 {
+		if Verbose {
+			fmt.Printf("%s:", cgodir)
+		}
+		err = RunExternal(CGoCMD, cgodir, cgo_argv)
+		if err != nil {
+			return
+		}
 	}
 
-	var allsrc = []string{filepath.Join("_cgo", "_obj", "_cgo_gotypes.go")}
+	var allsrc []string
+	if len(pkg.CGoSources) != 0 {
+		allsrc = append(allsrc, filepath.Join("_cgo", "_obj", "_cgo_gotypes.go"))
+	}
 	for _, src := range cgobases {
 		gs := src[:len(src)-3] + ".cgo1.go"
 		allsrc = append(allsrc, filepath.Join("_cgo", "_obj", gs))

gb/files.go

@@ -30,6 +30,7 @@ var (
 		"windows": true,
 		"darwin":  true,
 		"freebsd": true,
+		"openbsd": true,
 		"linux":   true,
 		"plan9":   true,
 	}
@@ -53,7 +54,7 @@ func CheckCGOFlag(flag string) bool {
 		return true
 	}
 	if flag == "bsd" &&
-		(GOOS == "darwin" || GOOS == "freebsd" || GOOS == "bsd") {
+		(GOOS == "darwin" || GOOS == "freebsd" || GOOS == "bsd" || GOOS == "openbsd") {
 		return true
 	}
 	return false

gb/gb.go

@@ -80,28 +80,48 @@ var WarnLog = log.New(os.Stderr, "gb warning: ", 0)
 /*
  gb doesn't know how to build these packages
 
- math has both pure go and asm versions of many functions, and which is used depends
- on the architexture
-
  go/build has a source-generation step that uses make variables
 
  os has source generation
 
- syscall has crazy pure go/asm versions and unused source files
+ syscall has files type_$(GOOS).go that aren't build, but can't reasonably be filtered
 
  crypto/tls has a file root_stub.go which is excluded
 */
 var ForceMakePkgs = map[string]bool{
 	//"math":       true,
 	"go/build":   true,
 	"os":         true,
+	"os/user":    true,
+	"net":        true,
 	"hash/crc32": true,
 	"syscall":    true,
 	"runtime":    true,
 	"crypto/tls": true,
 	"godoc":      true,
 }
 
+var DoNotBuildGOROOT = map[string]bool{
+	"src/cmd/5a":     true,
+	"src/cmd/5c":     true,
+	"src/cmd/5g":     true,
+	"src/cmd/5l":     true,
+	"src/cmd/6a":     true,
+	"src/cmd/6c":     true,
+	"src/cmd/6g":     true,
+	"src/cmd/6l":     true,
+	"src/cmd/8a":     true,
+	"src/cmd/8c":     true,
+	"src/cmd/8g":     true,
+	"src/cmd/8l":     true,
+	"src/cmd/cc":     true,
+	"src/cmd/gc":     true,
+	"src/cmd/cov":    true,
+	"src/cmd/gopack": true,
+	"src/cmd/nm":     true,
+	"src/cmd/prof":   true,
+}
+
 const (
 	ObjDir  = "_obj"
 	TestDir = "_test"

gb/pkg.go

@@ -163,6 +163,11 @@ func NewPackage(base, dir string, inTestData string, cfg Config) (this *Package,
 		return
 	}
 
+	if this.IsInGOROOT && DoNotBuildGOROOT[GetRelative(GOROOT, this.Dir, CWD)] {
+		err = errors.New("can't build GOROOT core tools")
+		return
+	}
+
 	if len(this.Sources) == 0 {
 		err = errors.New("no source")
 		return