cmd/link: compress debug sections in external linking mode

Forked from CL 111895.

For #11799.

Change-Id: Ie1346ac2c9122de494823b9058df3a0971e9dfe1
Reviewed-on: https://go-review.googlesource.com/118277
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index e6682606b62ed5ad2efd68fa71b228d2db36a0fe..fca6bdc1e2f55f81d5bd80a68e719f818ca5c2c7 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1221,6 +1221,11 @@ func (ctxt *Link) hostlink() {
                argv = append(argv, "-Qunused-arguments")
        }
 
+       const compressDWARF = "-Wl,--compress-debug-sections=zlib-gnu"
+       if linkerFlagSupported(argv[0], compressDWARF) {
+               argv = append(argv, compressDWARF)
+       }
+
        argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
        argv = append(argv, hostobjCopy()...)
 
@@ -1267,21 +1272,9 @@ func (ctxt *Link) hostlink() {
        // issue #17847. To avoid this problem pass -no-pie to the
        // toolchain if it is supported.
        if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared {
-               src := filepath.Join(*flagTmpdir, "trivial.c")
-               if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
-                       Errorf(nil, "WriteFile trivial.c failed: %v", err)
-               }
-
                // GCC uses -no-pie, clang uses -nopie.
                for _, nopie := range []string{"-no-pie", "-nopie"} {
-                       cmd := exec.Command(argv[0], nopie, "trivial.c")
-                       cmd.Dir = *flagTmpdir
-                       cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
-                       out, err := cmd.CombinedOutput()
-                       // GCC says "unrecognized command line option ‘-no-pie’"
-                       // clang says "unknown argument: '-no-pie'"
-                       supported := err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
-                       if supported {
+                       if linkerFlagSupported(argv[0], nopie) {
                                argv = append(argv, nopie)
                                break
                        }
@@ -1356,6 +1349,25 @@ func (ctxt *Link) hostlink() {
        }
 }
 
+var createTrivialCOnce sync.Once
+
+func linkerFlagSupported(linker, flag string) bool {
+       createTrivialCOnce.Do(func() {
+               src := filepath.Join(*flagTmpdir, "trivial.c")
+               if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
+                       Errorf(nil, "WriteFile trivial.c failed: %v", err)
+               }
+       })
+
+       cmd := exec.Command(linker, flag, "trivial.c")
+       cmd.Dir = *flagTmpdir
+       cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
+       out, err := cmd.CombinedOutput()
+       // GCC says "unrecognized command line option ‘-no-pie’"
+       // clang says "unknown argument: '-no-pie'"
+       return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
+}
+
 // hostlinkArchArgs returns arguments to pass to the external linker
 // based on the architecture.
 func hostlinkArchArgs(arch *sys.Arch) []string {