cmd/link: test the -s flag

Add a test checking the -s flag actually suppresses the symbol
table.

Change-Id: I7216d4811a72c62b823d2daa12f6462568243b12
Reviewed-on: https://go-review.googlesource.com/c/go/+/506759
Reviewed-by: Than McIntosh <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>

src/cmd/link/link_test.go

@@ -8,9 +8,11 @@ import (
  "bufio"
  "bytes"
  "debug/macho"
+ "errors"
  "internal/platform"
  "internal/testenv"
  "os"
+ "os/exec"
  "path/filepath"
  "regexp"
  "runtime"
@@ -1319,3 +1321,54 @@ func TestDynimportVar(t *testing.T) {
  }
  }
 }
+
+const helloSrc = `
+package main
+var X = 42
+var Y int
+func main() { println("hello", X, Y) }
+`
+
+func TestFlagS(t *testing.T) {
+ // Test that the -s flag strips the symbol table.
+ testenv.MustHaveGoBuild(t)
+
+ t.Parallel()
+
+ tmpdir := t.TempDir()
+ exe := filepath.Join(tmpdir, "a.exe")
+ src := filepath.Join(tmpdir, "a.go")
+ err := os.WriteFile(src, []byte(helloSrc), 0666)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ modes := []string{"auto"}
+ if testenv.HasCGO() {
+ modes = append(modes, "external")
+ }
+
+ // check a text symbol, a data symbol, and a BSS symbol
+ syms := []string{"main.main", "main.X", "main.Y"}
+
+ for _, mode := range modes {
+ cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-ldflags=-s -linkmode="+mode, "-o", exe, src)
+ out, err := cmd.CombinedOutput()
+ if err != nil {
+ t.Fatalf("build (linkmode=%s) failed: %v\n%s", mode, err, out)
+ }
+ cmd = testenv.Command(t, testenv.GoToolPath(t), "tool", "nm", exe)
+ out, err = cmd.CombinedOutput()
+ if err != nil && !errors.As(err, new(*exec.ExitError)) {
+ // Error exit is fine as it may have no symbols.
+ // On darwin we need to emit dynamic symbol references so it
+ // actually has some symbols, and nm succeeds.
+ t.Errorf("(mode=%s) go tool nm failed: %v\n%s", mode, err, out)
+ }
+ for _, s := range syms {
+ if bytes.Contains(out, []byte(s)) {
+ t.Errorf("(mode=%s): unexpected symbol %s", mode, s)
+ }
+ }
+ }
+}