test: add support for build tags.

This enables a few tests that were only executed
unconditionnally.

R=rsc, minux.ma, bradfitz
CC=golang-dev
https://golang.org/cl/7103051

test/fixedbugs/bug385_32.go

-// [ $A == 6 ] || errchk $G -e $D/$F.go
-
-// NOTE: This test is not run by 'run.go' and so not run by all.bash.
-// To run this test you must use the ./run shell script.
+// +build 386 arm
+// errorcheck
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/fixedbugs/bug385_64.go

-// [ $A != 6 ]  || errchk $G -e $D/$F.go
-
-// NOTE: This test is not run by 'run.go' and so not run by all.bash.
-// To run this test you must use the ./run shell script.
+// +build amd64
+// errorcheck
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/run.go

@@ -299,6 +299,50 @@ func goDirPackages(longdir string) ([][]string, error) {
 	return pkgs, nil
 }
 
+// shouldTest looks for build tags in a source file and returns
+// whether the file should be used according to the tags.
+func shouldTest(src string, goos, goarch string) (ok bool, whyNot string) {
+	if idx := strings.Index(src, "\npackage"); idx >= 0 {
+		src = src[:idx]
+	}
+	notgoos := "!" + goos
+	notgoarch := "!" + goarch
+	for _, line := range strings.Split(src, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "//") {
+			line = line[2:]
+		} else {
+			continue
+		}
+		line = strings.TrimSpace(line)
+		if len(line) == 0 || line[0] != '+' {
+			continue
+		}
+		words := strings.Fields(line)
+		if words[0] == "+build" {
+			for _, word := range words {
+				switch word {
+				case goos, goarch:
+					return true, ""
+				case notgoos, notgoarch:
+					continue
+				default:
+					if word[0] == '!' {
+						// NOT something-else
+						return true, ""
+					}
+				}
+			}
+			// no matching tag found.
+			return false, line
+		}
+	}
+	// no build tags.
+	return true, ""
+}
+
+func init() { checkShouldTest() }
+
 // run runs a test.
 func (t *test) run() {
 	defer close(t.donec)
@@ -318,7 +362,18 @@ func (t *test) run() {
 		t.err = errors.New("double newline not found")
 		return
 	}
+	if ok, why := shouldTest(t.src, runtime.GOOS, runtime.GOARCH); !ok {
+		t.action = "skip"
+		if *showSkips {
+			fmt.Printf("%-20s %-20s: %s\n", t.action, t.goFileName(), why)
+		}
+		return
+	}
 	action := t.src[:pos]
+	if nl := strings.Index(action, "\n"); nl >= 0 && strings.Contains(action[:nl], "+build") {
+		// skip first line
+		action = action[nl+1:]
+	}
 	if strings.HasPrefix(action, "//") {
 		action = action[2:]
 	}
@@ -732,16 +787,13 @@ func (t *test) wantedErrors(file, short string) (errs []wantedError) {
 }
 
 var skipOkay = map[string]bool{
-	"linkx.go":               true,
-	"sigchld.go":             true,
+	"linkx.go":            true, // like "run" but wants linker flags
 	"sinit.go":            true,
 	"fixedbugs/bug248.go": true, // combines errorcheckdir and rundir in the same dir.
 	"fixedbugs/bug302.go": true, // tests both .$O and .a imports.
 	"fixedbugs/bug345.go": true, // needs the appropriate flags in gc invocation.
 	"fixedbugs/bug369.go": true, // needs compiler flags.
-	"fixedbugs/bug385_32.go": true, // arch-specific errors.
-	"fixedbugs/bug385_64.go": true, // arch-specific errors.
-	"fixedbugs/bug429.go":    true,
+	"fixedbugs/bug429.go": true, // like "run" but program should fail
 	"bugs/bug395.go":      true,
 }
 
@@ -756,3 +808,18 @@ func defaultRunOutputLimit() int {
 	}
 	return cpu
 }
+
+// checkShouldTest runs canity checks on the shouldTest function.
+func checkShouldTest() {
+	assert := func(ok bool, _ string) {
+		if !ok {
+			panic("fail")
+		}
+	}
+	assertNot := func(ok bool, _ string) { assert(!ok, "") }
+	assert(shouldTest("// +build linux", "linux", "arm"))
+	assert(shouldTest("// +build !windows", "linux", "arm"))
+	assertNot(shouldTest("// +build !windows", "windows", "amd64"))
+	assertNot(shouldTest("// +build arm 386", "linux", "amd64"))
+	assert(shouldTest("// This is a test.", "os", "arch"))
+}

test/sigchld.go

-// [ "$GOOS" == windows ] ||
-// ($G $D/$F.go && $L $F.$A && ./$A.out 2>&1 | cmp - $D/$F.out)
-
-// NOTE: This test is not run by 'run.go' and so not run by all.bash.
-// To run this test you must use the ./run shell script.
+// +build !windows
+// cmpout
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/testlib

@@ -16,6 +16,31 @@ pkgs() {
 	done | sort
 }
 
+# +build aborts execution if the supplied tags don't match,
+# i.e. none of the tags (x or !x) matches GOARCH or GOOS.
++build() {
+	if (( $# == 0 )); then
+		return
+	fi
+	for tag; do
+		case $tag in
+		$GOARCH|$GOOS)
+			#echo >&2 "match $tag in $1"
+			return # don't exclude.
+			;;
+		'!'$GOARCH|'!'$GOOS)
+			;;
+		'!'*)
+			# not x where x is neither GOOS nor GOARCH.
+			#echo >&2 "match $tag in $1"
+			return # don't exclude
+			;;
+		esac
+	done
+	# no match.
+	exit 0
+}
+
 compile() {
 	$G $D/$F.go
 }