cmd/go: cgo programs depend on syscall

Fixes #5048.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/12651044

src/cmd/go/pkg.go

@@ -323,6 +323,23 @@ func expandScanner(err error) error {
 	return err
 }
 
+var raceExclude = map[string]bool{
+	"runtime/race": true,
+	"runtime/cgo":  true,
+	"cmd/cgo":      true,
+	"syscall":      true,
+	"errors":       true,
+}
+
+var cgoExclude = map[string]bool{
+	"runtime/cgo": true,
+}
+
+var cgoSyscallExclude = map[string]bool{
+	"runtime/cgo":  true,
+	"runtime/race": true,
+}
+
 // load populates p using information from bp, err, which should
 // be the result of calling build.Context.Import.
 func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package {
@@ -375,17 +392,22 @@ func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package
 	}
 
 	importPaths := p.Imports
-	// Packages that use cgo import runtime/cgo implicitly,
-	// except runtime/cgo itself.
-	if len(p.CgoFiles) > 0 && (!p.Standard || p.ImportPath != "runtime/cgo") {
+	// Packages that use cgo import runtime/cgo implicitly.
+	// Packages that use cgo also import syscall implicitly,
+	// to wrap errno.
+	// Exclude certain packages to avoid circular dependencies.
+	if len(p.CgoFiles) > 0 && (!p.Standard || !cgoExclude[p.ImportPath]) {
 		importPaths = append(importPaths, "runtime/cgo")
 	}
+	if len(p.CgoFiles) > 0 && (!p.Standard || !cgoSyscallExclude[p.ImportPath]) {
+		importPaths = append(importPaths, "syscall")
+	}
 	// Everything depends on runtime, except runtime and unsafe.
 	if !p.Standard || (p.ImportPath != "runtime" && p.ImportPath != "unsafe") {
 		importPaths = append(importPaths, "runtime")
 		// When race detection enabled everything depends on runtime/race.
-		// Exclude runtime/cgo and cmd/cgo to avoid circular dependencies.
-		if buildRace && (!p.Standard || (p.ImportPath != "runtime/race" && p.ImportPath != "runtime/cgo" && p.ImportPath != "cmd/cgo")) {
+		// Exclude certain packages to avoid circular dependencies.
+		if buildRace && (!p.Standard || !raceExclude[p.ImportPath]) {
 			importPaths = append(importPaths, "runtime/race")
 		}
 	}

src/cmd/go/test.bash

@@ -186,21 +186,21 @@ if [ ! -x $GOROOT/bin/godoc ]; then
 	ok=false
 fi
 
-TEST cmd/api installs into tool
+TEST cmd/fix installs into tool
 GOOS=$(./testgo env GOOS)
 GOARCH=$(./testgo env GOARCH)
-rm -f $GOROOT/pkg/tool/${GOOS}_${GOARCH}/api
-./testgo install cmd/api
-if [ ! -x $GOROOT/pkg/tool/${GOOS}_${GOARCH}/api ]; then
-	echo 'did not install cmd/api to $GOROOT/pkg/tool'
-	GOBIN=$d/gobin ./testgo list -f 'Target: {{.Target}}' cmd/api
+rm -f $GOROOT/pkg/tool/${GOOS}_${GOARCH}/fix
+./testgo install cmd/fix
+if [ ! -x $GOROOT/pkg/tool/${GOOS}_${GOARCH}/fix ]; then
+	echo 'did not install cmd/fix to $GOROOT/pkg/tool'
+	GOBIN=$d/gobin ./testgo list -f 'Target: {{.Target}}' cmd/fix
 	ok=false
 fi
-rm -f $GOROOT/pkg/tool/${GOOS}_${GOARCH}/api
-GOBIN=$d/gobin ./testgo install cmd/api
-if [ ! -x $GOROOT/pkg/tool/${GOOS}_${GOARCH}/api ]; then
-	echo 'did not install cmd/api to $GOROOT/pkg/tool with $GOBIN set'
-	GOBIN=$d/gobin ./testgo list -f 'Target: {{.Target}}' cmd/api
+rm -f $GOROOT/pkg/tool/${GOOS}_${GOARCH}/fix
+GOBIN=$d/gobin ./testgo install cmd/fix
+if [ ! -x $GOROOT/pkg/tool/${GOOS}_${GOARCH}/fix ]; then
+	echo 'did not install cmd/fix to $GOROOT/pkg/tool with $GOBIN set'
+	GOBIN=$d/gobin ./testgo list -f 'Target: {{.Target}}' cmd/fix
 	ok=false
 fi
 
@@ -434,20 +434,34 @@ elif ! grep "case-insensitive file name collision" $d/out >/dev/null; then
 fi
 
 TEST go get cover
-./testgo get code.google.com/p/go.tools/cmd/cover
+./testgo get code.google.com/p/go.tools/cmd/cover || ok=false
 
 unset GOPATH
 rm -rf $d
 
 # Only succeeds if source order is preserved.
 TEST source file name order preserved
-./testgo test testdata/example[12]_test.go
+./testgo test testdata/example[12]_test.go || ok=false
 
 # Check that coverage analysis works at all.
 # Don't worry about the exact numbers
 TEST coverage runs
-./testgo test -short -coverpkg=strings strings regexp
-./testgo test -short -cover strings math regexp
+./testgo test -short -coverpkg=strings strings regexp || ok=false
+./testgo test -short -cover strings math regexp || ok=false
+
+TEST cgo depends on syscall
+rm -rf $GOROOT/pkg/*_race
+d=$(TMPDIR=/var/tmp mktemp -d -t testgoXXX)
+export GOPATH=$d
+mkdir -p $d/src/foo
+echo '
+package foo
+//#include <stdio.h>
+import "C"
+' >$d/src/foo/foo.go
+./testgo build -race foo || ok=false
+rm -rf $d
+unset GOPATH
 
 # clean up
 if $started; then stop; fi