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cmd/go: fix "#cgo pkg-config:" comments with gccgo
The unique difficulty of #cgo pkg-config is that the linker flags are recorded when the package is compiled but (obviously) must be used when the package is linked into an executable -- so the flags need to be stored on disk somewhere. As it happens cgo already writes out a _cgo_flags file: nothing uses it currently, but this change adds it to the lib$pkg.a file when compiling a package, reads it out when linking (and passes a version of the .a file with _cgo_flags stripped out of it to the linker). It's all fairly ugly but it works and I can't really think of any way of reducing the essential level of ugliness. Fixes #11739 Change-Id: I35621878014e1e107eda77a5b0b23d0240ec5750 Reviewed-on: https://go-review.googlesource.com/18790 Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
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@ -1424,6 +1424,9 @@ func (b *builder) build(a *action) (err error) {
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if err != nil {
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return err
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}
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if _, ok := buildToolchain.(gccgoToolchain); ok {
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cgoObjects = append(cgoObjects, filepath.Join(a.objdir, "_cgo_flags"))
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}
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cgoObjects = append(cgoObjects, outObj...)
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gofiles = append(gofiles, outGo...)
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}
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@ -2610,12 +2613,73 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
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objc := len(root.p.MFiles) > 0
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fortran := len(root.p.FFiles) > 0
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readCgoFlags := func(flagsFile string) error {
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flags, err := ioutil.ReadFile(flagsFile)
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if err != nil {
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return err
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}
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const ldflagsPrefix = "_CGO_LDFLAGS="
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for _, line := range strings.Split(string(flags), "\n") {
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if strings.HasPrefix(line, ldflagsPrefix) {
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newFlags := strings.Fields(line[len(ldflagsPrefix):])
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for _, flag := range newFlags {
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// Every _cgo_flags file has -g and -O2 in _CGO_LDFLAGS
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// but they don't mean anything to the linker so filter
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// them out.
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if flag != "-g" && !strings.HasPrefix(flag, "-O") {
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cgoldflags = append(cgoldflags, flag)
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}
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}
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}
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}
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return nil
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}
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readAndRemoveCgoFlags := func(archive string) (string, error) {
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newa, err := ioutil.TempFile(b.work, filepath.Base(archive))
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if err != nil {
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return "", err
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}
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olda, err := os.Open(archive)
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if err != nil {
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return "", err
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}
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_, err = io.Copy(newa, olda)
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if err != nil {
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return "", err
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}
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err = olda.Close()
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if err != nil {
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return "", err
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}
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err = newa.Close()
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if err != nil {
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return "", err
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}
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newarchive := newa.Name()
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err = b.run(b.work, root.p.ImportPath, nil, "ar", "x", newarchive, "_cgo_flags")
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if err != nil {
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return "", err
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}
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err = b.run(".", root.p.ImportPath, nil, "ar", "d", newarchive, "_cgo_flags")
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if err != nil {
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return "", err
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}
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err = readCgoFlags(filepath.Join(b.work, "_cgo_flags"))
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if err != nil {
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return "", err
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}
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return newarchive, nil
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}
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actionsSeen := make(map[*action]bool)
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// Make a pre-order depth-first traversal of the action graph, taking note of
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// whether a shared library action has been seen on the way to an action (the
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// construction of the graph means that if any path to a node passes through
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// a shared library action, they all do).
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var walk func(a *action, seenShlib bool)
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var err error
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walk = func(a *action, seenShlib bool) {
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if actionsSeen[a] {
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return
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@ -2634,16 +2698,23 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
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// doesn't work.
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if !apackagesSeen[a.p] {
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apackagesSeen[a.p] = true
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target := a.target
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if len(a.p.CgoFiles) > 0 {
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target, err = readAndRemoveCgoFlags(target)
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if err != nil {
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return
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}
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}
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if a.p.fake && a.p.external {
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// external _tests, if present must come before
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// internal _tests. Store these on a separate list
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// and place them at the head after this loop.
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xfiles = append(xfiles, a.target)
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xfiles = append(xfiles, target)
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} else if a.p.fake {
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// move _test files to the top of the link order
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afiles = append([]string{a.target}, afiles...)
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afiles = append([]string{target}, afiles...)
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} else {
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afiles = append(afiles, a.target)
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afiles = append(afiles, target)
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}
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}
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}
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@ -2653,10 +2724,16 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
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}
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for _, a1 := range a.deps {
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walk(a1, seenShlib)
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if err != nil {
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return
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}
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}
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}
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for _, a1 := range root.deps {
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walk(a1, false)
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if err != nil {
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return err
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}
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}
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afiles = append(xfiles, afiles...)
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@ -2688,6 +2765,14 @@ func (tools gccgoToolchain) ld(b *builder, root *action, out string, allactions
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}
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}
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for i, o := range ofiles {
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if filepath.Base(o) == "_cgo_flags" {
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readCgoFlags(o)
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ofiles = append(ofiles[:i], ofiles[i+1:]...)
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break
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}
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}
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ldflags = append(ldflags, "-Wl,--whole-archive")
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ldflags = append(ldflags, afiles...)
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ldflags = append(ldflags, "-Wl,--no-whole-archive")
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