tests: autogenerated test to confirm attribute strings

Test helps verify our attribute types match the macros in textflag.h.
Discovered https://golang.org/issue/29487 in the process.

Updates #2

attr.go

@@ -83,14 +83,14 @@ func (a Attribute) split() ([]string, Attribute) {
 }
 
 var attrname = map[Attribute]string{
-	NOPROF:        "NOPROF",
-	DUPOK:         "DUPOK",
-	NOSPLIT:       "NOSPLIT",
-	RODATA:        "RODATA",
-	NOPTR:         "NOPTR",
-	WRAPPER:       "WRAPPER",
-	NEEDCTXT:      "NEEDCTXT",
-	TLSBSS:        "TLSBSS",
-	NOFRAME:       "NOFRAME",
-	REFLECTMETHOD: "REFLECTMETHOD",
+	NOPROF:   "NOPROF",
+	DUPOK:    "DUPOK",
+	NOSPLIT:  "NOSPLIT",
+	RODATA:   "RODATA",
+	NOPTR:    "NOPTR",
+	WRAPPER:  "WRAPPER",
+	NEEDCTXT: "NEEDCTXT",
+	TLSBSS:   "TLSBSS",
+	NOFRAME:  "NOFRAME",
+	// REFLECTMETHOD excluded due to https://golang.org/issue/29487
 }

attr_test.go

@@ -13,7 +13,8 @@ func TestAttributeAsm(t *testing.T) {
 		{DUPOK, "DUPOK"},
 		{RODATA | NOSPLIT, "NOSPLIT|RODATA"},
 		{WRAPPER | 16384 | NOPTR, "NOPTR|WRAPPER|16384"},
-		{NEEDCTXT + NOFRAME + TLSBSS + REFLECTMETHOD, "NEEDCTXT|TLSBSS|NOFRAME|REFLECTMETHOD"},
+		{NEEDCTXT + NOFRAME + TLSBSS, "NEEDCTXT|TLSBSS|NOFRAME"},
+		{REFLECTMETHOD, "1024"}, // REFLECTMETHOD special case due to https://golang.org/issue/29487
 	}
 	for _, c := range cases {
 		got := c.Attribute.Asm()

tests/textflag/attrtest_test.go

@@ -0,0 +1,13 @@
+package textflag
+
+import "testing"
+
+//go:generate go run make_attrtest.go -output zattrtest.s -seed 42 -num 256
+
+func AttrTest() bool
+
+func TestAttributes(t *testing.T) {
+	if !AttrTest() {
+		t.Fail()
+	}
+}

tests/textflag/make_attrtest.go

@@ -0,0 +1,88 @@
+// +build ignore
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"math/rand"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"github.com/mmcloughlin/avo"
+)
+
+var (
+	output = flag.String("output", "", "path to output file (default stdout)")
+	seed   = flag.Int64("seed", 0, "random seed")
+	num    = flag.Int("num", 32, "number of attributes to generate")
+)
+
+func GenerateAttributes(n int) []avo.Attribute {
+	as := make([]avo.Attribute, 0, n)
+
+	// Include each bitlevel.
+	for i := 0; i < 16 && i < n; i++ {
+		a := avo.Attribute(1 << uint(i))
+		as = append(as, a)
+	}
+
+	// Add randomly generated attributes.
+	for len(as) < n {
+		a := avo.Attribute(rand.Uint32())
+		as = append(as, a)
+	}
+
+	return as
+}
+
+func PrintAttributesTest(w io.Writer, as []avo.Attribute) {
+	_, self, _, _ := runtime.Caller(0)
+	fmt.Fprintf(w, "// Code generated by %s. DO NOT EDIT.\n\n", filepath.Base(self))
+	fmt.Fprintf(w, "#include \"textflag.h\"\n\n")
+	fmt.Fprintf(w, "TEXT ·AttrTest(SB), $0-1\n")
+	fmt.Fprintf(w, "\tMOVB $0, ret+0(FP)\n")
+
+	for i, a := range as {
+		fmt.Fprintf(w, "\tMOVW $(%d), R8\n", a)
+		fmt.Fprintf(w, "\tMOVW $(%s), R9\n", a.Asm())
+		fmt.Fprintf(w, "\tCMPW R8, R9\n")
+
+		cont := fmt.Sprintf("cont%d", i)
+		fmt.Fprintf(w, "\tJE %s\n", cont)
+		fmt.Fprintf(w, "\tRET\n")
+
+		fmt.Fprintf(w, "%s:\n", cont)
+	}
+
+	fmt.Fprintf(w, "\tMOVB $1, ret+0(FP)\n")
+	fmt.Fprintf(w, "\tRET\n")
+}
+
+func main() {
+	flag.Parse()
+
+	w := os.Stdout
+	if *output != "" {
+		f, err := os.Create(*output)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer f.Close()
+		w = f
+	}
+
+	rand.Seed(*seed)
+	as := GenerateAttributes(*num)
+
+	buf := bytes.NewBuffer(nil)
+	PrintAttributesTest(buf, as)
+
+	if _, err := w.Write(buf.Bytes()); err != nil {
+		log.Fatal(err)
+	}
+}