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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ld
import (
"cmd/internal/objabi"
"cmd/internal/sys"
"fmt"
"log"
)
var (
Linkmode LinkMode
Buildmode BuildMode
)
// A BuildMode indicates the sort of object we are building.
//
// Possible build modes are the same as those for the -buildmode flag
// in cmd/go, and are documented in 'go help buildmode'.
type BuildMode uint8
const (
BuildmodeUnset BuildMode = iota
BuildmodeExe
BuildmodePIE
BuildmodeCArchive
BuildmodeCShared
BuildmodeShared
BuildmodePlugin
)
func (mode *BuildMode) Set(s string) error {
badmode := func() error {
return fmt.Errorf("buildmode %s not supported on %s/%s", s, objabi.GOOS, objabi.GOARCH)
}
switch s {
default:
return fmt.Errorf("invalid buildmode: %q", s)
case "exe":
*mode = BuildmodeExe
case "pie":
switch objabi.GOOS {
case "android", "linux":
default:
return badmode()
}
*mode = BuildmodePIE
case "c-archive":
switch objabi.GOOS {
case "darwin", "linux":
case "windows":
switch objabi.GOARCH {
case "amd64", "386":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeCArchive
case "c-shared":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64":
default:
return badmode()
}
*mode = BuildmodeCShared
case "shared":
switch objabi.GOOS {
case "linux":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64", "ppc64le", "s390x":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeShared
case "plugin":
switch objabi.GOOS {
case "linux":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64", "s390x":
default:
return badmode()
}
case "darwin":
switch objabi.GOARCH {
case "amd64":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodePlugin
}
return nil
}
func (mode *BuildMode) String() string {
switch *mode {
case BuildmodeUnset:
return "" // avoid showing a default in usage message
case BuildmodeExe:
return "exe"
case BuildmodePIE:
return "pie"
case BuildmodeCArchive:
return "c-archive"
case BuildmodeCShared:
return "c-shared"
case BuildmodeShared:
return "shared"
case BuildmodePlugin:
return "plugin"
}
return fmt.Sprintf("BuildMode(%d)", uint8(*mode))
}
// LinkMode indicates whether an external linker is used for the final link.
type LinkMode uint8
const (
LinkAuto LinkMode = iota
LinkInternal
LinkExternal
)
func (mode *LinkMode) Set(s string) error {
switch s {
default:
return fmt.Errorf("invalid linkmode: %q", s)
case "auto":
*mode = LinkAuto
case "internal":
*mode = LinkInternal
case "external":
*mode = LinkExternal
}
return nil
}
func (mode *LinkMode) String() string {
switch *mode {
case LinkAuto:
return "auto"
case LinkInternal:
return "internal"
case LinkExternal:
return "external"
}
return fmt.Sprintf("LinkMode(%d)", uint8(*mode))
}
// mustLinkExternal reports whether the program being linked requires
// the external linker be used to complete the link.
func mustLinkExternal(ctxt *Link) (res bool, reason string) {
if ctxt.Debugvlog > 1 {
defer func() {
if res {
log.Printf("external linking is forced by: %s\n", reason)
}
}()
}
switch objabi.GOOS {
case "android":
return true, "android"
case "darwin":
if SysArch.InFamily(sys.ARM, sys.ARM64) {
return true, "iOS"
}
}
if *flagMsan {
return true, "msan"
}
// Internally linking cgo is incomplete on some architectures.
// https://golang.org/issue/10373
// https://golang.org/issue/14449
if iscgo && SysArch.InFamily(sys.ARM64, sys.MIPS64, sys.MIPS) {
return true, objabi.GOARCH + " does not support internal cgo"
}
// Some build modes require work the internal linker cannot do (yet).
switch Buildmode {
case BuildmodeCArchive:
return true, "buildmode=c-archive"
case BuildmodeCShared:
return true, "buildmode=c-shared"
case BuildmodePIE:
switch objabi.GOOS + "/" + objabi.GOARCH {
case "linux/amd64":
default:
// Internal linking does not support TLS_IE.
return true, "buildmode=pie"
}
case BuildmodePlugin:
return true, "buildmode=plugin"
case BuildmodeShared:
return true, "buildmode=shared"
}
if *FlagLinkshared {
return true, "dynamically linking with a shared library"
}
return false, ""
}
// determineLinkMode sets Linkmode.
//
// It is called after flags are processed and inputs are processed,
// so the Linkmode variable has an initial value from the -linkmode
// flag and the iscgo externalobj variables are set.
func determineLinkMode(ctxt *Link) {
switch Linkmode {
case LinkAuto:
// The environment variable GO_EXTLINK_ENABLED controls the
// default value of -linkmode. If it is not set when the
// linker is called we take the value it was set to when
// cmd/link was compiled. (See make.bash.)
switch objabi.Getgoextlinkenabled() {
case "0":
if needed, reason := mustLinkExternal(ctxt); needed {
Exitf("internal linking requested via GO_EXTLINK_ENABLED, but external linking required: %s", reason)
}
Linkmode = LinkInternal
case "1":
Linkmode = LinkExternal
default:
if needed, _ := mustLinkExternal(ctxt); needed {
Linkmode = LinkExternal
} else if iscgo && externalobj {
Linkmode = LinkExternal
} else if Buildmode == BuildmodePIE {
Linkmode = LinkExternal // https://golang.org/issue/18968
} else {
Linkmode = LinkInternal
}
}
case LinkInternal:
if needed, reason := mustLinkExternal(ctxt); needed {
Exitf("internal linking requested but external linking required: %s", reason)
}
}
}