cmd/internal/obj: add a flag to not write referenced symbol names in object file

The Go object file references (some of) symbols from other
packages by indices, not by names. The linker doesn't need the
symbol names to do the linking. The names are included in the
object file so it is self-contained and tools (objdump, nm) can
read the referenced symbol names. Including the names increases
object file size. Add a flag to disable it on demand (off by
default).

Change-Id: I143a0eb656997497c750b8eb1541341b2aee8f30
Reviewed-on: https://go-review.googlesource.com/c/go/+/404297
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/cmd/internal/obj/objfile_test.go b/src/cmd/internal/obj/objfile_test.go
index f5a4016eec..91e96e435d 100644
--- a/src/cmd/internal/obj/objfile_test.go
+++ b/src/cmd/internal/obj/objfile_test.go
@@ -121,3 +121,25 @@ func TestSymbolTooLarge(t *testing.T) { // Issue 42054
 		t.Errorf("unexpected error message: want: %q, got: %s", want, out)
 	}
 }
+
+func TestNoRefName(t *testing.T) {
+	// Test that the norefname flag works.
+	testenv.MustHaveGoBuild(t)
+
+	tmpdir := t.TempDir()
+
+	src := filepath.Join(tmpdir, "x.go")
+	err := ioutil.WriteFile(src, []byte("package main; import \"fmt\"; func main() { fmt.Println(123) }\n"), 0666)
+	if err != nil {
+		t.Fatalf("failed to write source file: %v\n", err)
+	}
+	exe := filepath.Join(tmpdir, "x.exe")
+
+	// Build the fmt package with norefname. Not rebuilding all packages to save time.
+	// Also testing that norefname and non-norefname packages can link together.
+	cmd := exec.Command(testenv.GoToolPath(t), "build", "-gcflags=fmt=-d=norefname", "-o", exe, src)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("build failed: %v, output:\n%s", err, out)
+	}
+}