src/cmd/link/internal/sym/attribute.go

// Copyright 2017 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 sym

// Attribute is a set of common symbol attributes.
type Attribute int16

const (
	// AttrDuplicateOK marks a symbol that can be present in multiple object
	// files.
	AttrDuplicateOK Attribute = 1 << iota
	// AttrExternal marks function symbols loaded from host object files.
	AttrExternal
	// AttrNoSplit marks functions that cannot split the stack; the linker
	// cares because it checks that there are no call chains of nosplit
	// functions that require more than StackLimit bytes (see
	// lib.go:dostkcheck)
	AttrNoSplit
	// AttrReachable marks symbols that are transitively referenced from the
	// entry points. Unreachable symbols are not written to the output.
	AttrReachable
	// AttrCgoExportDynamic and AttrCgoExportStatic mark symbols referenced
	// by directives written by cgo (in response to //export directives in
	// the source).
	AttrCgoExportDynamic
	AttrCgoExportStatic
	// AttrSpecial marks symbols that do not have their address (i.e. Value)
	// computed by the usual mechanism of data.go:dodata() &
	// data.go:address().
	AttrSpecial
	// AttrStackCheck is used by dostkcheck to only check each NoSplit
	// function's stack usage once.
	AttrStackCheck
	// AttrNotInSymbolTable marks symbols that are not written to the symbol table.
	AttrNotInSymbolTable
	// AttrOnList marks symbols that are on some list (such as the list of
	// all text symbols, or one of the lists of data symbols) and is
	// consulted to avoid bugs where a symbol is put on a list twice.
	AttrOnList
	// AttrLocal marks symbols that are only visible within the module
	// (executable or shared library) being linked. Only relevant when
	// dynamically linking Go code.
	AttrLocal
	// AttrReflectMethod marks certain methods from the reflect package that
	// can be used to call arbitrary methods. If no symbol with this bit set
	// is marked as reachable, more dead code elimination can be done.
	AttrReflectMethod
	// AttrMakeTypelink Amarks types that should be added to the typelink
	// table. See typelinks.go:typelinks().
	AttrMakeTypelink
	// AttrShared marks symbols compiled with the -shared option.
	AttrShared
	// 14 attributes defined so far.
)

func (a Attribute) DuplicateOK() bool      { return a&AttrDuplicateOK != 0 }
func (a Attribute) External() bool         { return a&AttrExternal != 0 }
func (a Attribute) NoSplit() bool          { return a&AttrNoSplit != 0 }
func (a Attribute) Reachable() bool        { return a&AttrReachable != 0 }
func (a Attribute) CgoExportDynamic() bool { return a&AttrCgoExportDynamic != 0 }
func (a Attribute) CgoExportStatic() bool  { return a&AttrCgoExportStatic != 0 }
func (a Attribute) Special() bool          { return a&AttrSpecial != 0 }
func (a Attribute) StackCheck() bool       { return a&AttrStackCheck != 0 }
func (a Attribute) NotInSymbolTable() bool { return a&AttrNotInSymbolTable != 0 }
func (a Attribute) OnList() bool           { return a&AttrOnList != 0 }
func (a Attribute) Local() bool            { return a&AttrLocal != 0 }
func (a Attribute) ReflectMethod() bool    { return a&AttrReflectMethod != 0 }
func (a Attribute) MakeTypelink() bool     { return a&AttrMakeTypelink != 0 }
func (a Attribute) Shared() bool           { return a&AttrShared != 0 }

func (a Attribute) CgoExport() bool {
	return a.CgoExportDynamic() || a.CgoExportStatic()
}

func (a *Attribute) Set(flag Attribute, value bool) {
	if value {
		*a |= flag
	} else {
		*a &^= flag
	}
}