cmd/go: hide work subdirectory names in gcc/clang object files

Until now the subdirectories under $WORK have had predictable
names, so it was OK to strip just $WORK from the file names that
end up in object files. In the future, those predictable names would
cause predictable collisions when compiling one package in two
different ways, so we're moving toward arbitrary, unpredictable
subdirectory names instead. When we do that, if the names appear
in the object files we won't get reproducible builds.

Take the subdirectory names out now, to make the later change safe.

Change-Id: I8057d1cc73f6e35c98b7718c9789c161dcbd87c0
Reviewed-on: https://go-review.googlesource.com/67251
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/internal/envcmd/env.go

@@ -73,10 +73,10 @@ func MkEnv() []cfg.EnvVar {
 		env = append(env, cfg.EnvVar{Name: "GO386", Value: cfg.GO386})
 	}
 
-	cmd := b.GccCmd(".")
+	cmd := b.GccCmd(".", "")
 	env = append(env, cfg.EnvVar{Name: "CC", Value: cmd[0]})
 	env = append(env, cfg.EnvVar{Name: "GOGCCFLAGS", Value: strings.Join(cmd[3:], " ")})
-	cmd = b.GxxCmd(".")
+	cmd = b.GxxCmd(".", "")
 	env = append(env, cfg.EnvVar{Name: "CXX", Value: cmd[0]})
 
 	if cfg.BuildContext.CgoEnabled {

src/cmd/go/internal/work/build.go

@@ -3157,18 +3157,18 @@ func gccgoCleanPkgpath(p *load.Package) string {
 }
 
 // gcc runs the gcc C compiler to create an object from a single C file.
-func (b *Builder) gcc(p *load.Package, out string, flags []string, cfile string) error {
-	return b.ccompile(p, out, flags, cfile, b.GccCmd(p.Dir))
+func (b *Builder) gcc(p *load.Package, workdir, out string, flags []string, cfile string) error {
+	return b.ccompile(p, out, flags, cfile, b.GccCmd(p.Dir, workdir))
 }
 
 // gxx runs the g++ C++ compiler to create an object from a single C++ file.
-func (b *Builder) gxx(p *load.Package, out string, flags []string, cxxfile string) error {
-	return b.ccompile(p, out, flags, cxxfile, b.GxxCmd(p.Dir))
+func (b *Builder) gxx(p *load.Package, workdir, out string, flags []string, cxxfile string) error {
+	return b.ccompile(p, out, flags, cxxfile, b.GxxCmd(p.Dir, workdir))
 }
 
 // gfortran runs the gfortran Fortran compiler to create an object from a single Fortran file.
-func (b *Builder) gfortran(p *load.Package, out string, flags []string, ffile string) error {
-	return b.ccompile(p, out, flags, ffile, b.gfortranCmd(p.Dir))
+func (b *Builder) gfortran(p *load.Package, workdir, out string, flags []string, ffile string) error {
+	return b.ccompile(p, out, flags, ffile, b.gfortranCmd(p.Dir, workdir))
 }
 
 // ccompile runs the given C or C++ compiler and creates an object from a single source file.
@@ -3211,41 +3211,41 @@ func (b *Builder) ccompile(p *load.Package, outfile string, flags []string, file
 }
 
 // gccld runs the gcc linker to create an executable from a set of object files.
-func (b *Builder) gccld(p *load.Package, out string, flags []string, objs []string) error {
+func (b *Builder) gccld(p *load.Package, objdir, out string, flags []string, objs []string) error {
 	var cmd []string
 	if len(p.CXXFiles) > 0 || len(p.SwigCXXFiles) > 0 {
-		cmd = b.GxxCmd(p.Dir)
+		cmd = b.GxxCmd(p.Dir, objdir)
 	} else {
-		cmd = b.GccCmd(p.Dir)
+		cmd = b.GccCmd(p.Dir, objdir)
 	}
 	return b.run(p.Dir, p.ImportPath, nil, cmd, "-o", out, objs, flags)
 }
 
 // gccCmd returns a gcc command line prefix
 // defaultCC is defined in zdefaultcc.go, written by cmd/dist.
-func (b *Builder) GccCmd(objdir string) []string {
-	return b.compilerCmd("CC", cfg.DefaultCC, objdir)
+func (b *Builder) GccCmd(incdir, workdir string) []string {
+	return b.compilerCmd("CC", cfg.DefaultCC, incdir, workdir)
 }
 
 // gxxCmd returns a g++ command line prefix
 // defaultCXX is defined in zdefaultcc.go, written by cmd/dist.
-func (b *Builder) GxxCmd(objdir string) []string {
-	return b.compilerCmd("CXX", cfg.DefaultCXX, objdir)
+func (b *Builder) GxxCmd(incdir, workdir string) []string {
+	return b.compilerCmd("CXX", cfg.DefaultCXX, incdir, workdir)
 }
 
 // gfortranCmd returns a gfortran command line prefix.
-func (b *Builder) gfortranCmd(objdir string) []string {
-	return b.compilerCmd("FC", "gfortran", objdir)
+func (b *Builder) gfortranCmd(incdir, workdir string) []string {
+	return b.compilerCmd("FC", "gfortran", incdir, workdir)
 }
 
 // compilerCmd returns a command line prefix for the given environment
 // variable and using the default command when the variable is empty.
-func (b *Builder) compilerCmd(envvar, defcmd, objdir string) []string {
+func (b *Builder) compilerCmd(envvar, defcmd, incdir, workdir string) []string {
 	// NOTE: env.go's mkEnv knows that the first three
-	// strings returned are "gcc", "-I", objdir (and cuts them off).
+	// strings returned are "gcc", "-I", incdir (and cuts them off).
 
 	compiler := envList(envvar, defcmd)
-	a := []string{compiler[0], "-I", objdir}
+	a := []string{compiler[0], "-I", incdir}
 	a = append(a, compiler[1:]...)
 
 	// Definitely want -fPIC but on Windows gcc complains
@@ -3279,7 +3279,11 @@ func (b *Builder) compilerCmd(envvar, defcmd, objdir string) []string {
 
 	// Tell gcc not to include the work directory in object files.
 	if b.gccSupportsFlag(compiler, "-fdebug-prefix-map=a=b") {
-		a = append(a, "-fdebug-prefix-map="+b.WorkDir+"=/tmp/go-build")
+		if workdir == "" {
+			workdir = b.WorkDir
+		}
+		workdir = strings.TrimSuffix(workdir, string(filepath.Separator))
+		a = append(a, "-fdebug-prefix-map="+workdir+"=/tmp/go-build")
 	}
 
 	// Tell gcc not to include flags in object files, which defeats the
@@ -3508,7 +3512,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 	cflags := str.StringList(cgoCPPFLAGS, cgoCFLAGS)
 	for _, cfile := range cfiles {
 		ofile := nextOfile()
-		if err := b.gcc(p, ofile, cflags, objdir+cfile); err != nil {
+		if err := b.gcc(p, a.Objdir, ofile, cflags, objdir+cfile); err != nil {
 			return nil, nil, err
 		}
 		outObj = append(outObj, ofile)
@@ -3516,7 +3520,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 
 	for _, file := range gccfiles {
 		ofile := nextOfile()
-		if err := b.gcc(p, ofile, cflags, file); err != nil {
+		if err := b.gcc(p, a.Objdir, ofile, cflags, file); err != nil {
 			return nil, nil, err
 		}
 		outObj = append(outObj, ofile)
@@ -3525,7 +3529,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 	cxxflags := str.StringList(cgoCPPFLAGS, cgoCXXFLAGS)
 	for _, file := range gxxfiles {
 		ofile := nextOfile()
-		if err := b.gxx(p, ofile, cxxflags, file); err != nil {
+		if err := b.gxx(p, a.Objdir, ofile, cxxflags, file); err != nil {
 			return nil, nil, err
 		}
 		outObj = append(outObj, ofile)
@@ -3533,7 +3537,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 
 	for _, file := range mfiles {
 		ofile := nextOfile()
-		if err := b.gcc(p, ofile, cflags, file); err != nil {
+		if err := b.gcc(p, a.Objdir, ofile, cflags, file); err != nil {
 			return nil, nil, err
 		}
 		outObj = append(outObj, ofile)
@@ -3542,7 +3546,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 	fflags := str.StringList(cgoCPPFLAGS, cgoFFLAGS)
 	for _, file := range ffiles {
 		ofile := nextOfile()
-		if err := b.gfortran(p, ofile, fflags, file); err != nil {
+		if err := b.gfortran(p, a.Objdir, ofile, fflags, file); err != nil {
 			return nil, nil, err
 		}
 		outObj = append(outObj, ofile)
@@ -3577,7 +3581,7 @@ func (b *Builder) cgo(a *Action, cgoExe, objdir string, pcCFLAGS, pcLDFLAGS, cgo
 func (b *Builder) dynimport(p *load.Package, objdir, importGo, cgoExe string, cflags, cgoLDFLAGS, outObj []string) error {
 	cfile := objdir + "_cgo_main.c"
 	ofile := objdir + "_cgo_main.o"
-	if err := b.gcc(p, ofile, cflags, cfile); err != nil {
+	if err := b.gcc(p, objdir, ofile, cflags, cfile); err != nil {
 		return err
 	}
 
@@ -3589,7 +3593,7 @@ func (b *Builder) dynimport(p *load.Package, objdir, importGo, cgoExe string, cf
 	if (cfg.Goarch == "arm" && cfg.Goos == "linux") || cfg.Goos == "android" {
 		ldflags = append(ldflags, "-pie")
 	}
-	if err := b.gccld(p, dynobj, ldflags, linkobj); err != nil {
+	if err := b.gccld(p, objdir, dynobj, ldflags, linkobj); err != nil {
 		return err
 	}