cmd/link/internal/ld: remove flags incompatible with -fembed-bitcode

The flags -headerpad, -Wl,-no_pie and -pagezero_size are incompatible with
the -fembed-bitcode flag used by `gomobile build`. Than McIntosh
suggested we might not need the offending flags; this change removes
the flags on darwin/arm64 and -headerpad, -pagezero_size on darwin/arm.

The -Wl,-no_pie flag is left for darwin/arm because linking fails
without it:

ld: warning: PIE disabled. Absolute addressing (perhaps -mdynamic-no-pic) not allowed in code signed PIE, but used in _runtime.rodata from /var/folders/qq/qxn86k813bn9fjxydm095rxw0000gp/T/workdir-host-darwin-amd64-zenly-ios/tmp/go-link-225285265/go.o. To fix this warning, don't compile with -mdynamic-no-pic or link with -Wl,-no_pie

Discussion: https://groups.google.com/d/msg/golang-dev/U1jK3xmmGAk/j0_ty46EDAAJ

I've verified the CL on the builders, built the "flappy" example from
gomobile with `gomobile build`, and verified that flappy runs on an
iPhone 5S.

Updates #32963

Change-Id: I783abc93ccf3c1d2b7ca00144b7164ba223d3529
Reviewed-on: https://go-review.googlesource.com/c/go/+/201358
Reviewed-by: Cherry Zhang <cherryyz@google.com>

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 308d506fc3d8a363d3cdcedce4825196fa0027dc..9d99aa6f28b895ced9baebd24186b372480f0b09 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1169,13 +1169,13 @@ func (ctxt *Link) hostlink() {
 
        switch ctxt.HeadType {
        case objabi.Hdarwin:
-               argv = append(argv, "-Wl,-headerpad,1144")
+               if !ctxt.Arch.InFamily(sys.ARM, sys.ARM64) {
+                       // -headerpad is incompatible with -fembed-bitcode.
+                       argv = append(argv, "-Wl,-headerpad,1144")
+               }
                if ctxt.DynlinkingGo() && !ctxt.Arch.InFamily(sys.ARM, sys.ARM64) {
                        argv = append(argv, "-Wl,-flat_namespace")
                }
-               if ctxt.BuildMode == BuildModeExe && !ctxt.Arch.InFamily(sys.ARM64) {
-                       argv = append(argv, "-Wl,-no_pie")
-               }
        case objabi.Hopenbsd:
                argv = append(argv, "-Wl,-nopie")
        case objabi.Hwindows:
@@ -1209,11 +1209,10 @@ func (ctxt *Link) hostlink() {
        switch ctxt.BuildMode {
        case BuildModeExe:
                if ctxt.HeadType == objabi.Hdarwin {
-                       if ctxt.Arch.Family == sys.ARM64 {
-                               // __PAGEZERO segment size determined empirically.
-                               // XCode 9.0.1 successfully uploads an iOS app with this value.
-                               argv = append(argv, "-Wl,-pagezero_size,100000000")
-                       } else {
+                       if ctxt.Arch.Family != sys.ARM64 {
+                               argv = append(argv, "-Wl,-no_pie")
+                       }
+                       if !ctxt.Arch.InFamily(sys.ARM, sys.ARM64) {
                                argv = append(argv, "-Wl,-pagezero_size,4000000")
                        }
                }