cmd/go: combine gccgo's ld and ldShared methods

This fixes handling of cgo flags and makes sure packages that are only
implicitly included in the shared library are passed to the link.

Fixes #15885

Change-Id: I1e8a72b5314261973ca903c78834700fb113dde9
Reviewed-on: https://go-review.googlesource.com/23537Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/build.go

@@ -2625,7 +2625,7 @@ func (gccgoToolchain) pack(b *builder, p *Package, objDir, afile string, ofiles
 	return b.run(p.Dir, p.ImportPath, nil, "ar", "rc", mkAbs(objDir, afile), absOfiles)
 }
 
-func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions []*action, mainpkg string, ofiles []string) error {
+func (tools gccgoToolchain) link(b *builder, root *action, out string, allactions []*action, mainpkg string, ofiles []string, buildmode, desc string) error {
 	// gccgo needs explicit linking with all package dependencies,
 	// and all LDFLAGS from cgo dependencies.
 	apackagePathsSeen := make(map[string]bool)
@@ -2634,9 +2634,14 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 	ldflags := b.gccArchArgs()
 	cgoldflags := []string{}
 	usesCgo := false
-	cxx := len(root.p.CXXFiles) > 0 || len(root.p.SwigCXXFiles) > 0
-	objc := len(root.p.MFiles) > 0
-	fortran := len(root.p.FFiles) > 0
+	cxx := false
+	objc := false
+	fortran := false
+	if root.p != nil {
+		cxx = len(root.p.CXXFiles) > 0 || len(root.p.SwigCXXFiles) > 0
+		objc = len(root.p.MFiles) > 0
+		fortran = len(root.p.FFiles) > 0
+	}
 
 	readCgoFlags := func(flagsFile string) error {
 		flags, err := ioutil.ReadFile(flagsFile)
@@ -2683,11 +2688,11 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 		}
 
 		newarchive := newa.Name()
-		err = b.run(b.work, root.p.ImportPath, nil, "ar", "x", newarchive, "_cgo_flags")
+		err = b.run(b.work, desc, nil, "ar", "x", newarchive, "_cgo_flags")
 		if err != nil {
 			return "", err
 		}
-		err = b.run(".", root.p.ImportPath, nil, "ar", "d", newarchive, "_cgo_flags")
+		err = b.run(".", desc, nil, "ar", "d", newarchive, "_cgo_flags")
 		if err != nil {
 			return "", err
 		}
@@ -2793,7 +2798,9 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 
 	ldflags = append(ldflags, cgoldflags...)
 	ldflags = append(ldflags, envList("CGO_LDFLAGS", "")...)
-	ldflags = append(ldflags, root.p.CgoLDFLAGS...)
+	if root.p != nil {
+		ldflags = append(ldflags, root.p.CgoLDFLAGS...)
+	}
 
 	ldflags = stringList("-Wl,-(", ldflags, "-Wl,-)")
 
@@ -2808,7 +2815,7 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 	}
 
 	var realOut string
-	switch ldBuildmode {
+	switch buildmode {
 	case "exe":
 		if usesCgo && goos == "linux" {
 			ldflags = append(ldflags, "-Wl,-E")
@@ -2843,12 +2850,14 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 
 	case "c-shared":
 		ldflags = append(ldflags, "-shared", "-nostdlib", "-Wl,--whole-archive", "-lgolibbegin", "-Wl,--no-whole-archive", "-lgo", "-lgcc_s", "-lgcc", "-lc", "-lgcc")
+	case "shared":
+		ldflags = append(ldflags, "-zdefs", "-shared", "-nostdlib", "-lgo", "-lgcc_s", "-lgcc", "-lc")
 
 	default:
-		fatalf("-buildmode=%s not supported for gccgo", ldBuildmode)
+		fatalf("-buildmode=%s not supported for gccgo", buildmode)
 	}
 
-	switch ldBuildmode {
+	switch buildmode {
 	case "exe", "c-shared":
 		if cxx {
 			ldflags = append(ldflags, "-lstdc++")
@@ -2869,41 +2878,27 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
 		}
 	}
 
-	if err := b.run(".", root.p.ImportPath, nil, tools.linker(), "-o", out, ofiles, ldflags, buildGccgoflags); err != nil {
+	if err := b.run(".", desc, nil, tools.linker(), "-o", out, ofiles, ldflags, buildGccgoflags); err != nil {
 		return err
 	}
 
-	switch ldBuildmode {
+	switch buildmode {
 	case "c-archive":
-		if err := b.run(".", root.p.ImportPath, nil, "ar", "rc", realOut, out); err != nil {
+		if err := b.run(".", desc, nil, "ar", "rc", realOut, out); err != nil {
 			return err
 		}
 	}
 	return nil
 }
 
+func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions []*action, mainpkg string, ofiles []string) error {
+	return tools.link(b, root, out, allactions, mainpkg, ofiles, ldBuildmode, root.p.ImportPath)
+}
+
 func (tools gccgoToolchain) ldShared(b *builder, toplevelactions []*action, out string, allactions []*action) error {
-	args := []string{"-o", out, "-shared", "-nostdlib", "-zdefs", "-Wl,--whole-archive"}
-	for _, a := range toplevelactions {
-		args = append(args, a.target)
-	}
-	args = append(args, "-Wl,--no-whole-archive", "-shared", "-nostdlib", "-lgo", "-lgcc_s", "-lgcc", "-lc")
-	shlibs := []string{}
-	for _, a := range allactions {
-		if strings.HasSuffix(a.target, ".so") {
-			shlibs = append(shlibs, a.target)
-		}
-	}
-	for _, shlib := range shlibs {
-		args = append(
-			args,
-			"-L"+filepath.Dir(shlib),
-			"-Wl,-rpath="+filepath.Dir(shlib),
-			"-l"+strings.TrimSuffix(
-				strings.TrimPrefix(filepath.Base(shlib), "lib"),
-				".so"))
-	}
-	return b.run(".", out, nil, tools.linker(), args, buildGccgoflags)
+	fakeRoot := &action{}
+	fakeRoot.deps = toplevelactions
+	return tools.link(b, fakeRoot, out, allactions, "", nil, "shared", out)
 }
 
 func (tools gccgoToolchain) cc(b *builder, p *Package, objdir, ofile, cfile string) error {