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/21607
Reviewed-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_test.go

@@ -0,0 +1,79 @@
+// 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
+		}
+	}
+}