cmd/compile: cleanup pragcgo

Removes dynimport, dynexport, dynlinker cases since they can not
be reached due to prefix check for "go:cgo_" in getlinepragma.

Replaces the if chains for verb distinction by a switch statement.
Replaces fmt.Sprintf by fmt.Sprintln for string concatenation.

Removes the more, getimpsym and getquoted functions by introducing a
pragmaFields function that partitions a pragma into its components.

Adds tests for cgo pragmas.

Change-Id: I43c7b9550feb3ddccaff7fb02198a3f994444123
Reviewed-on: https://go-review.googlesource.com/21607Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/lex.go

@@ -44,6 +44,10 @@ func isDigit(c rune) bool {
 	return '0' <= c && c <= '9'
 }
 
+func isQuoted(s string) bool {
+	return len(s) >= 2 && s[0] == '"' && s[len(s)-1] == '"'
+}
+
 func plan9quote(s string) string {
 	if s == "" {
 		return "''"
@@ -853,15 +857,6 @@ func internString(b []byte) string {
 	return s
 }
 
-func more(pp *string) bool {
-	p := *pp
-	for p != "" && isSpace(rune(p[0])) {
-		p = p[1:]
-	}
-	*pp = p
-	return p != ""
-}
-
 // read and interpret syntax that looks like
 // //line parse.y:15
 // as a discontinuity in sequential line numbers.
@@ -887,7 +882,7 @@ func (l *lexer) getlinepragma() rune {
 		text := strings.TrimSuffix(lexbuf.String(), "\r")
 
 		if strings.HasPrefix(text, "go:cgo_") {
-			pragcgo(text)
+			pragcgobuf += pragcgo(text)
 		}
 
 		verb := text
@@ -991,139 +986,114 @@ func (l *lexer) getlinepragma() rune {
 	return c
 }
 
-func getimpsym(pp *string) string {
-	more(pp) // skip spaces
-	p := *pp
-	if p == "" || p[0] == '"' {
-		return ""
-	}
-	i := 0
-	for i < len(p) && !isSpace(rune(p[i])) && p[i] != '"' {
-		i++
-	}
-	sym := p[:i]
-	*pp = p[i:]
-	return sym
-}
+func pragcgo(text string) string {
+	f := pragmaFields(text)
 
-func getquoted(pp *string) (string, bool) {
-	more(pp) // skip spaces
-	p := *pp
-	if p == "" || p[0] != '"' {
-		return "", false
-	}
-	p = p[1:]
-	i := strings.Index(p, `"`)
-	if i < 0 {
-		return "", false
-	}
-	*pp = p[i+1:]
-	return p[:i], true
-}
+	verb := f[0][3:] // skip "go:"
+	switch verb {
+	case "cgo_export_static", "cgo_export_dynamic":
+		switch {
+		case len(f) == 2 && !isQuoted(f[1]):
+			local := plan9quote(f[1])
+			return fmt.Sprintln(verb, local)
 
-// Copied nearly verbatim from the C compiler's #pragma parser.
-// TODO: Rewrite more cleanly once the compiler is written in Go.
-func pragcgo(text string) {
-	var q string
+		case len(f) == 3 && !isQuoted(f[1]) && !isQuoted(f[2]):
+			local := plan9quote(f[1])
+			remote := plan9quote(f[2])
+			return fmt.Sprintln(verb, local, remote)
 
-	if i := strings.Index(text, " "); i >= 0 {
-		text, q = text[:i], text[i:]
+		default:
+			Yyerror(`usage: //go:%s local [remote]`, verb)
 		}
+	case "cgo_import_dynamic":
+		switch {
+		case len(f) == 2 && !isQuoted(f[1]):
+			local := plan9quote(f[1])
+			return fmt.Sprintln(verb, local)
 
-	verb := text[3:] // skip "go:"
+		case len(f) == 3 && !isQuoted(f[1]) && !isQuoted(f[2]):
+			local := plan9quote(f[1])
+			remote := plan9quote(f[2])
+			return fmt.Sprintln(verb, local, remote)
 
-	if verb == "cgo_dynamic_linker" || verb == "dynlinker" {
-		p, ok := getquoted(&q)
-		if !ok {
-			Yyerror("usage: //go:cgo_dynamic_linker \"path\"")
-			return
-		}
-		pragcgobuf += fmt.Sprintf("cgo_dynamic_linker %v\n", plan9quote(p))
-		return
+		case len(f) == 4 && !isQuoted(f[1]) && !isQuoted(f[2]) && isQuoted(f[3]):
+			local := plan9quote(f[1])
+			remote := plan9quote(f[2])
+			library := plan9quote(strings.Trim(f[3], `"`))
+			return fmt.Sprintln(verb, local, remote, library)
 
+		default:
+			Yyerror(`usage: //go:cgo_import_dynamic local [remote ["library"]]`)
 		}
+	case "cgo_import_static":
+		switch {
+		case len(f) == 2 && !isQuoted(f[1]):
+			local := plan9quote(f[1])
+			return fmt.Sprintln(verb, local)
 
-	if verb == "dynexport" {
-		verb = "cgo_export_dynamic"
-	}
-	if verb == "cgo_export_static" || verb == "cgo_export_dynamic" {
-		local := getimpsym(&q)
-		var remote string
-		if local == "" {
-			goto err2
-		}
-		if !more(&q) {
-			pragcgobuf += fmt.Sprintf("%s %v\n", verb, plan9quote(local))
-			return
+		default:
+			Yyerror(`usage: //go:cgo_import_static local`)
 		}
+	case "cgo_dynamic_linker":
+		switch {
+		case len(f) == 2 && isQuoted(f[1]):
+			path := plan9quote(strings.Trim(f[1], `"`))
+			return fmt.Sprintln(verb, path)
 
-		remote = getimpsym(&q)
-		if remote == "" {
-			goto err2
-		}
-		pragcgobuf += fmt.Sprintf("%s %v %v\n", verb, plan9quote(local), plan9quote(remote))
-		return
-
-	err2:
-		Yyerror("usage: //go:%s local [remote]", verb)
-		return
+		default:
+			Yyerror(`usage: //go:cgo_dynamic_linker "path"`)
 		}
+	case "cgo_ldflag":
+		switch {
+		case len(f) == 2 && isQuoted(f[1]):
+			arg := plan9quote(strings.Trim(f[1], `"`))
+			return fmt.Sprintln(verb, arg)
 
-	if verb == "cgo_import_dynamic" || verb == "dynimport" {
-		var ok bool
-		local := getimpsym(&q)
-		var p string
-		var remote string
-		if local == "" {
-			goto err3
+		default:
+			Yyerror(`usage: //go:cgo_ldflag "arg"`)
 		}
-		if !more(&q) {
-			pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v\n", plan9quote(local))
-			return
 	}
+	return ""
+}
 
-		remote = getimpsym(&q)
-		if remote == "" {
-			goto err3
+// pragmaFields is similar to strings.FieldsFunc(s, isSpace)
+// but does not split when inside double quoted regions and always
+// splits before the start and after the end of a double quoted region.
+// pragmaFields does not recognize escaped quotes. If a quote in s is not
+// closed the part after the opening quote will not be returned as a field.
+func pragmaFields(s string) []string {
+	var a []string
+	inQuote := false
+	fieldStart := -1 // Set to -1 when looking for start of field.
+	for i, c := range s {
+		switch {
+		case c == '"':
+			if inQuote {
+				inQuote = false
+				a = append(a, s[fieldStart:i+1])
+				fieldStart = -1
+			} else {
+				inQuote = true
+				if fieldStart >= 0 {
+					a = append(a, s[fieldStart:i])
 				}
-		if !more(&q) {
-			pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v %v\n", plan9quote(local), plan9quote(remote))
-			return
+				fieldStart = i
 			}
-
-		p, ok = getquoted(&q)
-		if !ok {
-			goto err3
+		case !inQuote && isSpace(c):
+			if fieldStart >= 0 {
+				a = append(a, s[fieldStart:i])
+				fieldStart = -1
 			}
-		pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v %v %v\n", plan9quote(local), plan9quote(remote), plan9quote(p))
-		return
-
-	err3:
-		Yyerror("usage: //go:cgo_import_dynamic local [remote [\"library\"]]")
-		return
-	}
-
-	if verb == "cgo_import_static" {
-		local := getimpsym(&q)
-		if local == "" || more(&q) {
-			Yyerror("usage: //go:cgo_import_static local")
-			return
+		default:
+			if fieldStart == -1 {
+				fieldStart = i
 			}
-		pragcgobuf += fmt.Sprintf("cgo_import_static %v\n", plan9quote(local))
-		return
-
 		}
-
-	if verb == "cgo_ldflag" {
-		p, ok := getquoted(&q)
-		if !ok {
-			Yyerror("usage: //go:cgo_ldflag \"arg\"")
-			return
 	}
-		pragcgobuf += fmt.Sprintf("cgo_ldflag %v\n", plan9quote(p))
-		return
-
+	if !inQuote && fieldStart >= 0 { // Last field might end at the end of the string.
+		a = append(a, s[fieldStart:])
 	}
+	return a
 }
 
 func (l *lexer) getr() rune {

src/cmd/compile/internal/gc/lex_test.go

+// Copyright 2016 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 gc
+
+import "testing"
+
+func eq(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := 0; i < len(a); i++ {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func TestPragmaFields(t *testing.T) {
+
+	var tests = []struct {
+		in   string
+		want []string
+	}{
+		{"", []string{}},
+		{" \t ", []string{}},
+		{`""""`, []string{`""`, `""`}},
+		{"  a'b'c  ", []string{"a'b'c"}},
+		{"1 2 3 4", []string{"1", "2", "3", "4"}},
+		{"\n☺\t☹\n", []string{"☺", "☹"}},
+		{`"1 2 "  3  " 4 5"`, []string{`"1 2 "`, `3`, `" 4 5"`}},
+		{`"1""2 3""4"`, []string{`"1"`, `"2 3"`, `"4"`}},
+		{`12"34"`, []string{`12`, `"34"`}},
+		{`12"34 `, []string{`12`}},
+	}
+
+	for _, tt := range tests {
+		got := pragmaFields(tt.in)
+		if !eq(got, tt.want) {
+			t.Errorf("pragmaFields(%q) = %v; want %v", tt.in, got, tt.want)
+			continue
+		}
+	}
+}
+
+func TestPragcgo(t *testing.T) {
+
+	var tests = []struct {
+		in   string
+		want string
+	}{
+		{`go:cgo_export_dynamic local`, "cgo_export_dynamic local\n"},
+		{`go:cgo_export_dynamic local remote`, "cgo_export_dynamic local remote\n"},
+		{`go:cgo_export_dynamic local' remote'`, "cgo_export_dynamic 'local''' 'remote'''\n"},
+		{`go:cgo_export_static local`, "cgo_export_static local\n"},
+		{`go:cgo_export_static local remote`, "cgo_export_static local remote\n"},
+		{`go:cgo_export_static local' remote'`, "cgo_export_static 'local''' 'remote'''\n"},
+		{`go:cgo_import_dynamic local`, "cgo_import_dynamic local\n"},
+		{`go:cgo_import_dynamic local remote`, "cgo_import_dynamic local remote\n"},
+		{`go:cgo_import_dynamic local remote "library"`, "cgo_import_dynamic local remote library\n"},
+		{`go:cgo_import_dynamic local' remote' "lib rary"`, "cgo_import_dynamic 'local''' 'remote''' 'lib rary'\n"},
+		{`go:cgo_import_static local`, "cgo_import_static local\n"},
+		{`go:cgo_import_static local'`, "cgo_import_static 'local'''\n"},
+		{`go:cgo_dynamic_linker "/path/"`, "cgo_dynamic_linker /path/\n"},
+		{`go:cgo_dynamic_linker "/p ath/"`, "cgo_dynamic_linker '/p ath/'\n"},
+		{`go:cgo_ldflag "arg"`, "cgo_ldflag arg\n"},
+		{`go:cgo_ldflag "a rg"`, "cgo_ldflag 'a rg'\n"},
+	}
+
+	for _, tt := range tests {
+		got := pragcgo(tt.in)
+		if got != tt.want {
+			t.Errorf("pragcgo(%q) = %q; want %q", tt.in, got, tt.want)
+			continue
+		}
+	}
+}