misc/cgo/testcshared: don't rely on an erroneous install target in tests

Non-main packages in module mode should not be installed to
GOPATH/pkg, but due to #37015 they were installed there anyway.

This change switches the 'go install' command in createHeaders to
instead use 'go build' (with an extension determined by the install
target for 'runtime/cgo', which is well-defined at least for the
moment), and switches TestCachedInstall (which appears to be
explicitly testing 'go install') to explicitly request GOPATH mode
(which provides a well-defined install target for the library).

This change follows a similar structure to CL 416954.

For #37015.

Change-Id: I22ae4af0f0d4c50adc9e0f0dc279859d1f258cc8
Reviewed-on: https://go-review.googlesource.com/c/go/+/417096
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

diff --git a/misc/cgo/testcshared/cshared_test.go b/misc/cgo/testcshared/cshared_test.go
index e4898778be80ed9c9ea07d205b064bfd086be070..7fbcff24dd7ce57df4c6d0d756321be11ef739c5 100644 (file)
--- a/misc/cgo/testcshared/cshared_test.go
+++ b/misc/cgo/testcshared/cshared_test.go
@@ -151,16 +151,22 @@ func testMain(m *testing.M) int {
        // The installation directory format varies depending on the platform.
        output, err := exec.Command("go", "list",
                "-buildmode=c-shared",
-               "-installsuffix", "testcshared",
                "-f", "{{.Target}}",
-               "./libgo").CombinedOutput()
+               "runtime/cgo").CombinedOutput()
        if err != nil {
                log.Panicf("go list failed: %v\n%s", err, output)
        }
-       target := string(bytes.TrimSpace(output))
-       libgoname = filepath.Base(target)
-       installdir = filepath.Dir(target)
-       libSuffix = strings.TrimPrefix(filepath.Ext(target), ".")
+       runtimeCgoTarget := string(bytes.TrimSpace(output))
+       libSuffix = strings.TrimPrefix(filepath.Ext(runtimeCgoTarget), ".")
+
+       defer func() {
+               if installdir != "" {
+                       err := os.RemoveAll(installdir)
+                       if err != nil {
+                               log.Panic(err)
+                       }
+               }
+       }()
 
        return m.Run()
 }
@@ -284,8 +290,13 @@ func createHeaders() error {
        }
 
        // Generate a C header file for libgo itself.
-       args = []string{"go", "install", "-buildmode=c-shared",
-               "-installsuffix", "testcshared", "./libgo"}
+       installdir, err = os.MkdirTemp("", "testcshared")
+       if err != nil {
+               return err
+       }
+       libgoname = "libgo." + libSuffix
+
+       args = []string{"go", "build", "-buildmode=c-shared", "-o", filepath.Join(installdir, libgoname), "./libgo"}
        cmd = exec.Command(args[0], args[1:]...)
        out, err = cmd.CombinedOutput()
        if err != nil {
@@ -373,6 +384,7 @@ func createHeadersOnce(t *testing.T) {
                headersErr = createHeaders()
        })
        if headersErr != nil {
+               t.Helper()
                t.Fatal(headersErr)
        }
 }
@@ -705,12 +717,15 @@ func TestCachedInstall(t *testing.T) {
        copyFile(t, filepath.Join(tmpdir, "src", "testcshared", "libgo", "libgo.go"), filepath.Join("libgo", "libgo.go"))
        copyFile(t, filepath.Join(tmpdir, "src", "testcshared", "p", "p.go"), filepath.Join("p", "p.go"))
 
-       env := append(os.Environ(), "GOPATH="+tmpdir, "GOBIN="+filepath.Join(tmpdir, "bin"))
-
        buildcmd := []string{"go", "install", "-x", "-buildmode=c-shared", "-installsuffix", "testcshared", "./libgo"}
 
        cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
        cmd.Dir = filepath.Join(tmpdir, "src", "testcshared")
+       env := append(cmd.Environ(),
+               "GOPATH="+tmpdir,
+               "GOBIN="+filepath.Join(tmpdir, "bin"),
+               "GO111MODULE=off", // 'go install' only works in GOPATH mode
+       )
        cmd.Env = env
        t.Log(buildcmd)
        out, err := cmd.CombinedOutput()