cmd/link: move issue 43830 tests out of TestScript

These tests pass or fail depending on the exact compiler version,
which the TestScript tests don't support. Rewrite into Go.

For #43830
For #46295

Change-Id: I91b61dfe329d518e461ee56f186f0e9b42858e77
Reviewed-on: https://go-review.googlesource.com/c/go/+/324049
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/go/testdata/script/cgo_lto2_issue43830.txt

@@ -1,33 +0,0 @@
-# tests golang.org/issue/43830
-
-[!cgo] skip 'skipping test without cgo'
-[openbsd] env CC='clang'
-[openbsd] [!exec:clang] skip 'skipping test without clang present'
-[!openbsd] env CC='gcc'
-[!openbsd] [!exec:gcc] skip 'skipping test without gcc present'
-
-env CGO_CFLAGS='-Wno-ignored-optimization-argument -flto -ffat-lto-objects'
-
-go build main.go
-
--- main.go --
-
-package main
-
-import "fmt"
-
-// #include "hello.h"
-import "C"
-
-func main() {
-	hello := C.hello
-	fmt.Printf("%v\n", hello)
-}
-
--- hello.h --
-
-#include <stdio.h>
-
-void hello(void) {
-  printf("hello\n");
-}

src/cmd/go/testdata/script/cgo_lto_issue43830.txt

@@ -1,40 +0,0 @@
-# tests golang.org/issue/43830
-
-[!cgo] skip 'skipping test without cgo'
-[openbsd] env CC='clang'
-[openbsd] [!exec:clang] skip 'skipping test without clang present'
-[!openbsd] env CC='gcc'
-[!openbsd] [!exec:gcc] skip 'skipping test without gcc present'
-
-env CGO_CFLAGS='-Wno-ignored-optimization-argument -flto -ffat-lto-objects'
-
-go build main.go add.go
-
--- main.go --
-
-package main
-
-/*
-extern int myadd(int, int);
-int c_add(int a, int b) {
-	return myadd(a, b);
-}
-*/
-import "C"
-
-func main() {
-	println(C.c_add(1, 2))
-}
-
--- add.go --
-
-package main
-
-import "C"
-
-/* test */
-
-//export myadd
-func myadd(a C.int, b C.int) C.int {
-	return a + b
-}

src/cmd/link/cgo_test.go

@@ -0,0 +1,138 @@
+// Copyright 2021 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 main
+
+import (
+	"bytes"
+	"fmt"
+	"internal/testenv"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+// Issues 43830, 46295
+func TestCGOLTO(t *testing.T) {
+	testenv.MustHaveCGO(t)
+	testenv.MustHaveGoBuild(t)
+
+	t.Parallel()
+
+	for _, cc := range []string{"gcc", "clang"} {
+		for test := 0; test < 2; test++ {
+			t.Run(fmt.Sprintf("%s-%d", cc, test), func(t *testing.T) {
+				testCGOLTO(t, cc, test)
+			})
+		}
+	}
+}
+
+const test1_main = `
+package main
+
+/*
+extern int myadd(int, int);
+int c_add(int a, int b) {
+	return myadd(a, b);
+}
+*/
+import "C"
+
+func main() {
+	println(C.c_add(1, 2))
+}
+`
+
+const test1_add = `
+package main
+
+import "C"
+
+/* test */
+
+//export myadd
+func myadd(a C.int, b C.int) C.int {
+	return a + b
+}
+`
+
+const test2_main = `
+package main
+
+import "fmt"
+
+/*
+#include <stdio.h>
+
+void hello(void) {
+  printf("hello\n");
+}
+*/
+import "C"
+
+func main() {
+	hello := C.hello
+	fmt.Printf("%v\n", hello)
+}
+`
+
+func testCGOLTO(t *testing.T, cc string, test int) {
+	t.Parallel()
+
+	if _, err := exec.LookPath(cc); err != nil {
+		t.Skipf("no %s compiler", cc)
+	}
+
+	dir := t.TempDir()
+
+	writeTempFile := func(name, contents string) {
+		if err := os.WriteFile(filepath.Join(dir, name), []byte(contents), 0644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	writeTempFile("go.mod", "module cgolto\n")
+
+	switch test {
+	case 0:
+		writeTempFile("main.go", test1_main)
+		writeTempFile("add.go", test1_add)
+	case 1:
+		writeTempFile("main.go", test2_main)
+	default:
+		t.Fatalf("bad case %d", test)
+	}
+
+	cmd := exec.Command(testenv.GoToolPath(t), "build")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(),
+		"CC="+cc,
+		"CGO_CFLAGS=-flto",
+	)
+
+	t.Log("go build")
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+
+	if err != nil {
+		t.Logf("go build failed: %v", err)
+
+		// Error messages we've seen indicating that LTO is not supported.
+		var noLTO = []string{
+			`unrecognized command line option "-flto"`,
+			"unable to pass LLVM bit-code files to linker",
+			"file not recognized: File format not recognized",
+			"LTO support has not been enabled",
+		}
+		for _, msg := range noLTO {
+			if bytes.Contains(out, []byte(msg)) {
+				t.Skipf("C compiler %v does not support LTO", cc)
+			}
+		}
+
+		t.Error("failed")
+	}
+}