cmd/go: link SWIG objects directly rather than using a shared library

This change requires using SWIG version 3.0 or later.  Earlier
versions of SWIG do not generate the pragmas required to use
the external linker.

Fixes issue 7155.
Fixes issue 7156.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://codereview.appspot.com/97120046

4 files changed, 26 insertions, 112 deletions

diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index 78ff9ade3..a6a21317e 100644
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -1048,21 +1048,6 @@ func (b *builder) install(a *action) (err error) {
 		defer os.Remove(a1.target)
 	}
 
-	if a.p.usesSwig() {
-		for _, f := range stringList(a.p.SwigFiles, a.p.SwigCXXFiles) {
-			dir = a.p.swigDir(&buildContext)
-			if err := b.mkdir(dir); err != nil {
-				return err
-			}
-			soname := a.p.swigSoname(f)
-			source := filepath.Join(a.objdir, soname)
-			target := filepath.Join(dir, soname)
-			if err = b.copyFile(a, target, source, perm); err != nil {
-				return err
-			}
-		}
-	}
-
 	return b.moveOrCopyFile(a, a.target, a1.target, perm)
 }
 
@@ -1721,25 +1706,8 @@ func packInternal(b *builder, afile string, ofiles []string) error {
 
 func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action, mainpkg string, ofiles []string) error {
 	importArgs := b.includeArgs("-L", allactions)
-	swigDirs := make(map[string]bool)
-	swigArg := []string{}
 	cxx := false
 	for _, a := range allactions {
-		if a.p != nil && a.p.usesSwig() {
-			sd := a.p.swigDir(&buildContext)
-			if len(swigArg) == 0 {
-				swigArg = []string{"-r", sd}
-			} else if !swigDirs[sd] {
-				swigArg[1] += ":"
-				swigArg[1] += sd
-			}
-			swigDirs[sd] = true
-			if a.objdir != "" && !swigDirs[a.objdir] {
-				swigArg[1] += ":"
-				swigArg[1] += a.objdir
-				swigDirs[a.objdir] = true
-			}
-		}
 		if a.p != nil && len(a.p.CXXFiles) > 0 {
 			cxx = true
 		}
@@ -1792,7 +1760,7 @@ func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action,
 			}
 		}
 	}
-	return b.run(".", p.ImportPath, nil, tool(archChar+"l"), "-o", out, importArgs, swigArg, ldflags, mainpkg)
+	return b.run(".", p.ImportPath, nil, tool(archChar+"l"), "-o", out, importArgs, ldflags, mainpkg)
 }
 
 func (gcToolchain) cc(b *builder, p *Package, objdir, ofile, cfile string) error {
@@ -1865,7 +1833,6 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
 	// and all LDFLAGS from cgo dependencies.
 	apackagesSeen := make(map[*Package]bool)
 	afiles := []string{}
-	sfiles := []string{}
 	ldflags := b.gccArchArgs()
 	cgoldflags := []string{}
 	usesCgo := false
@@ -1898,14 +1865,6 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
 				usesCgo = true
 			}
 			if a.p.usesSwig() {
-				sd := a.p.swigDir(&buildContext)
-				if a.objdir != "" {
-					sd = a.objdir
-				}
-				for _, f := range stringList(a.p.SwigFiles, a.p.SwigCXXFiles) {
-					soname := a.p.swigSoname(f)
-					sfiles = append(sfiles, filepath.Join(sd, soname))
-				}
 				usesCgo = true
 			}
 			if len(a.p.CXXFiles) > 0 {
@@ -1917,7 +1876,6 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
 		}
 	}
 	ldflags = append(ldflags, afiles...)
-	ldflags = append(ldflags, sfiles...)
 	ldflags = append(ldflags, cgoldflags...)
 	ldflags = append(ldflags, p.CgoLDFLAGS...)
 	if usesCgo && goos == "linux" {
@@ -2364,13 +2322,12 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 	cflags := stringList(cgoCPPFLAGS, cgoCFLAGS)
 	cxxflags := stringList(cgoCPPFLAGS, cgoCXXFLAGS)
 
-	var extraObj []string
 	for _, file := range gccfiles {
 		ofile := obj + cgoRe.ReplaceAllString(file[:len(file)-1], "_") + "o"
 		if err := b.gcc(p, ofile, cflags, file); err != nil {
 			return nil, nil, err
 		}
-		extraObj = append(extraObj, ofile)
+		outObj = append(outObj, ofile)
 	}
 
 	for _, file := range gxxfiles {
@@ -2379,7 +2336,7 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 		if err := b.gxx(p, ofile, cxxflags, file); err != nil {
 			return nil, nil, err
 		}
-		extraObj = append(extraObj, ofile)
+		outObj = append(outObj, ofile)
 	}
 
 	for _, file := range mfiles {
@@ -2388,7 +2345,7 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 		if err := b.gcc(p, ofile, cflags, file); err != nil {
 			return nil, nil, err
 		}
-		extraObj = append(extraObj, ofile)
+		outObj = append(outObj, ofile)
 	}
 
 	intgosize, err := b.swigIntSize(obj)
@@ -2397,7 +2354,7 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 	}
 
 	for _, f := range p.SwigFiles {
-		goFile, objFile, err := b.swigOne(p, f, obj, false, intgosize, extraObj)
+		goFile, objFile, gccObjFile, err := b.swigOne(p, f, obj, false, intgosize)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -2407,9 +2364,12 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 		if objFile != "" {
 			outObj = append(outObj, objFile)
 		}
+		if gccObjFile != "" {
+			outObj = append(outObj, gccObjFile)
+		}
 	}
 	for _, f := range p.SwigCXXFiles {
-		goFile, objFile, err := b.swigOne(p, f, obj, true, intgosize, extraObj)
+		goFile, objFile, gccObjFile, err := b.swigOne(p, f, obj, true, intgosize)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -2419,6 +2379,9 @@ func (b *builder) swig(p *Package, obj string, gccfiles, gxxfiles, mfiles []stri
 		if objFile != "" {
 			outObj = append(outObj, objFile)
 		}
+		if gccObjFile != "" {
+			outObj = append(outObj, gccObjFile)
+		}
 	}
 	return outGo, outObj, nil
 }
@@ -2450,13 +2413,13 @@ func (b *builder) swigIntSize(obj string) (intsize string, err error) {
 }
 
 // Run SWIG on one SWIG input file.
-func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize string, extraObj []string) (outGo, outObj string, err error) {
-	cgoCPPFLAGS, cgoCFLAGS, cgoCXXFLAGS, cgoLDFLAGS := b.cflags(p, true)
+func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize string) (outGo, outObj, objGccObj string, err error) {
+	cgoCPPFLAGS, cgoCFLAGS, cgoCXXFLAGS, _ := b.cflags(p, true)
 	var cflags []string
 	if cxx {
-		cflags = stringList(cgoCPPFLAGS, cgoCXXFLAGS, "-fPIC")
+		cflags = stringList(cgoCPPFLAGS, cgoCXXFLAGS)
 	} else {
-		cflags = stringList(cgoCPPFLAGS, cgoCFLAGS, "-fPIC")
+		cflags = stringList(cgoCPPFLAGS, cgoCFLAGS)
 	}
 
 	n := 5 // length of ".swig"
@@ -2471,7 +2434,6 @@ func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize stri
 	if cxx {
 		gccExt = "cxx"
 	}
-	soname := p.swigSoname(file)
 
 	_, gccgo := buildToolchain.(gccgoToolchain)
 
@@ -2480,12 +2442,14 @@ func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize stri
 		"-go",
 		"-intgosize", intgosize,
 		"-module", base,
-		"-soname", soname,
 		"-o", obj + gccBase + gccExt,
 		"-outdir", obj,
 	}
 	if gccgo {
 		args = append(args, "-gccgo")
+		if pkgpath := gccgoPkgpath(p); pkgpath != "" {
+			args = append(args, "-go-pkgpath", pkgpath)
+		}
 	}
 	if cxx {
 		args = append(args, "-c++")
@@ -2494,12 +2458,12 @@ func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize stri
 	if out, err := b.runOut(p.Dir, p.ImportPath, nil, "swig", args, file); err != nil {
 		if len(out) > 0 {
 			if bytes.Contains(out, []byte("Unrecognized option -intgosize")) {
-				return "", "", errors.New("must have SWIG version >= 2.0.9\n")
+				return "", "", "", errors.New("must have SWIG version >= 3.0\n")
 			}
 			b.showOutput(p.Dir, p.ImportPath, b.processOutput(out))
-			return "", "", errPrintedOutput
+			return "", "", "", errPrintedOutput
 		}
-		return "", "", err
+		return "", "", "", err
 	}
 
 	var cObj string
@@ -2507,7 +2471,7 @@ func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize stri
 		// cc
 		cObj = obj + cBase + archChar
 		if err := buildToolchain.cc(b, p, obj, cObj, obj+cBase+"c"); err != nil {
-			return "", "", err
+			return "", "", "", err
 		}
 	}
 
@@ -2515,32 +2479,15 @@ func (b *builder) swigOne(p *Package, file, obj string, cxx bool, intgosize stri
 	gccObj := obj + gccBase + "o"
 	if !cxx {
 		if err := b.gcc(p, gccObj, cflags, obj+gccBase+gccExt); err != nil {
-			return "", "", err
+			return "", "", "", err
 		}
 	} else {
 		if err := b.gxx(p, gccObj, cflags, obj+gccBase+gccExt); err != nil {
-			return "", "", err
+			return "", "", "", err
 		}
 	}
 
-	// create shared library
-	osldflags := map[string][]string{
-		"darwin":  {"-dynamiclib", "-Wl,-undefined,dynamic_lookup"},
-		"freebsd": {"-shared", "-lpthread", "-lm"},
-		"linux":   {"-shared", "-lpthread", "-lm"},
-		"windows": {"-shared", "-lm", "-mthreads"},
-	}
-	var cxxlib []string
-	if cxx {
-		cxxlib = []string{"-lstdc++"}
-	}
-	ldflags := stringList(osldflags[goos], cflags, cgoLDFLAGS, cxxlib)
-	target := filepath.Join(obj, soname)
-	if err := b.run(p.Dir, p.ImportPath, nil, b.gccCmd(p.Dir), "-o", target, gccObj, extraObj, ldflags); err != nil {
-		return "", "", err
-	}
-
-	return obj + goFile, cObj, nil
+	return obj + goFile, cObj, gccObj, nil
 }
 
 // An actionQueue is a priority queue of actions.
diff --git a/src/cmd/go/clean.go b/src/cmd/go/clean.go
index 3028193bc..16054a5b5 100644
--- a/src/cmd/go/clean.go
+++ b/src/cmd/go/clean.go
@@ -216,20 +216,6 @@ func clean(p *Package) {
 		}
 	}
 
-	if cleanI && p.usesSwig() {
-		for _, f := range stringList(p.SwigFiles, p.SwigCXXFiles) {
-			dir := p.swigDir(&buildContext)
-			soname := p.swigSoname(f)
-			target := filepath.Join(dir, soname)
-			if buildN || buildX {
-				b.showcmd("", "rm -f %s", target)
-			}
-			if !buildN {
-				removeFile(target)
-			}
-		}
-	}
-
 	if cleanR {
 		for _, p1 := range p.imports {
 			clean(p1)
diff --git a/src/cmd/go/doc.go b/src/cmd/go/doc.go
index 7fe0008a0..05dc9c2bd 100644
--- a/src/cmd/go/doc.go
+++ b/src/cmd/go/doc.go
@@ -144,7 +144,6 @@ source directories corresponding to the import paths:
 	DIR(.exe)        from go build
 	DIR.test(.exe)   from go test -c
 	MAINFILE(.exe)   from go build MAINFILE.go
-	*.so             from SWIG
 
 In the list, DIR represents the final path element of the
 directory, and MAINFILE is the base name of any Go source
diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
index 59c5d357e..7c78f8e66 100644
--- a/src/cmd/go/pkg.go
+++ b/src/cmd/go/pkg.go
@@ -560,24 +560,6 @@ func (p *Package) usesCgo() bool {
 	return len(p.CgoFiles) > 0
 }
 
-// swigSoname returns the name of the shared library we create for a
-// SWIG input file.
-func (p *Package) swigSoname(file string) string {
-	return strings.Replace(p.ImportPath, "/", "-", -1) + "-" + strings.Replace(file, ".", "-", -1) + ".so"
-}
-
-// swigDir returns the name of the shared SWIG directory for a
-// package.
-func (p *Package) swigDir(ctxt *build.Context) string {
-	dir := p.build.PkgRoot
-	if ctxt.Compiler == "gccgo" {
-		dir = filepath.Join(dir, "gccgo_"+ctxt.GOOS+"_"+ctxt.GOARCH)
-	} else {
-		dir = filepath.Join(dir, ctxt.GOOS+"_"+ctxt.GOARCH)
-	}
-	return filepath.Join(dir, "swig")
-}
-
 // packageList returns the list of packages in the dag rooted at roots
 // as visited in a depth-first post-order traversal.
 func packageList(roots []*Package) []*Package {