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[dev.link] cmd/link: expand set of symbol attributes in loader
Add in a collection of new loader interfaces for getting/setting
symbol attributes, e.g. properties that would normally be part of the
sym.Symbol "Attr" field. This change also moves references to the
loaders 'reachable' bitmap behind a pair of loader methods, so that we
a consistent way of accessing symbol attributes overall. It is worth
noting that not every symbol attribute is backed by a bitmap; for some
infrequently used attributes, a map[Sym]struct{} is used instead.
Change-Id: I0010c9cd928d41b4bb6cdf45db4581e11c3c5db3
Reviewed-on: https://go-review.googlesource.com/c/go/+/210778
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Than McIntosh
parent
07914eda40
commit
b658c62e9c
3 changed files with 312 additions and 27 deletions
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@ -76,13 +76,19 @@ type nameVer struct {
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type bitmap []uint32
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// set the i-th bit.
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func (bm bitmap) Set(i Sym) {
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func (bm bitmap) set(i Sym) {
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n, r := uint(i)/32, uint(i)%32
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bm[n] |= 1 << r
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}
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// unset the i-th bit.
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func (bm bitmap) unset(i Sym) {
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n, r := uint(i)/32, uint(i)%32
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bm[n] &^= (1 << r)
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}
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// whether the i-th bit is set.
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func (bm bitmap) Has(i Sym) bool {
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func (bm bitmap) has(i Sym) bool {
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n, r := uint(i)/32, uint(i)%32
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return bm[n]&(1<<r) != 0
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}
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@ -100,7 +106,7 @@ func makeBitmap(n int) bitmap {
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func growBitmap(reqLen int, b bitmap) bitmap {
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curLen := b.len()
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if reqLen > curLen {
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b = append(b, makeBitmap(reqLen-curLen)...)
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b = append(b, makeBitmap(reqLen+1-curLen)...)
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}
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return b
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}
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@ -161,7 +167,22 @@ type Loader struct {
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anonVersion int // most recently assigned ext static sym pseudo-version
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Reachable bitmap // bitmap of reachable symbols, indexed by global index
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// Bitmaps and other side structures used to store data used to store
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// symbol flags/attributes; these are to be accessed via the
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// corresponding loader "AttrXXX" and "SetAttrXXX" methods. Please
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// visit the comments on these methods for more details on the
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// semantics / interpretation of the specific flags or attribute.
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attrReachable bitmap // reachable symbols, indexed by global index
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attrOnList bitmap // "on list" symbols, indexed by global index
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attrVisibilityHidden bitmap // hidden symbols, indexed by ext sym index
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attrDuplicateOK bitmap // dupOK symbols, indexed by ext sym index
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attrShared bitmap // shared symbols, indexed by ext sym index
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attrExternal bitmap // external symbols, indexed by ext sym index
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attrTopFrame map[Sym]struct{} // top frame symbols
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attrSpecial map[Sym]struct{} // "special" frame symbols
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attrCgoExportDynamic map[Sym]struct{} // "cgo_export_dynamic" symbols
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attrCgoExportStatic map[Sym]struct{} // "cgo_export_static" symbols
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// Used to implement field tracking; created during deadcode if
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// field tracking is enabled. Reachparent[K] contains the index of
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@ -343,7 +364,8 @@ func (l *Loader) getPayload(i Sym) *extSymPayload {
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return &l.payloads[pi]
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}
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// Ensure Syms slice has enough space.
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// Ensure Syms slice has enough space, as well as growing the
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// 'payloads' slice.
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func (l *Loader) growSyms(i int) {
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n := len(l.Syms)
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if n > i {
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@ -351,7 +373,7 @@ func (l *Loader) growSyms(i int) {
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}
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l.Syms = append(l.Syms, make([]*sym.Symbol, i+1-n)...)
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l.payloads = append(l.payloads, make([]extSymPayload, i+1-n)...)
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l.growReachable(int(i))
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l.growAttrBitmaps(int(i) + 1)
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}
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// Convert a local index to a global index.
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@ -586,6 +608,212 @@ func (l *Loader) SymAttr(i Sym) uint8 {
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return osym.Flag
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}
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// AttrReachable returns true for symbols that are transitively
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// referenced from the entry points. Unreachable symbols are not
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// written to the output.
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func (l *Loader) AttrReachable(i Sym) bool {
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return l.attrReachable.has(i)
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}
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// SetAttrReachable sets the reachability property for a symbol (see
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// AttrReachable).
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func (l *Loader) SetAttrReachable(i Sym, v bool) {
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if v {
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l.attrReachable.set(i)
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} else {
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l.attrReachable.unset(i)
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}
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}
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// AttrOnList returns true for symbols that are on some list (such as
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// the list of all text symbols, or one of the lists of data symbols)
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// and is consulted to avoid bugs where a symbol is put on a list
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// twice.
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func (l *Loader) AttrOnList(i Sym) bool {
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return l.attrOnList.has(i)
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}
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// SetAttrOnList sets the "on list" property for a symbol (see
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// AttrOnList).
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func (l *Loader) SetAttrOnList(i Sym, v bool) {
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if v {
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l.attrOnList.set(i)
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} else {
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l.attrOnList.unset(i)
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}
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}
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// AttrVisibilityHidden symbols returns true for ELF symbols with
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// visibility set to STV_HIDDEN. They become local symbols in
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// the final executable. Only relevant when internally linking
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// on an ELF platform.
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func (l *Loader) AttrVisibilityHidden(i Sym) bool {
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if i < l.extStart {
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return false
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}
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return l.attrVisibilityHidden.has(i - l.extStart)
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}
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// SetAttrVisibilityHidden sets the "hidden visibility" property for a
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// symbol (see AttrVisibilityHidden).
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func (l *Loader) SetAttrVisibilityHidden(i Sym, v bool) {
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if i < l.extStart {
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panic("tried to set visibility attr on non-external symbol")
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}
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if v {
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l.attrVisibilityHidden.set(i - l.extStart)
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} else {
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l.attrVisibilityHidden.unset(i - l.extStart)
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}
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}
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// AttrDuplicateOK returns true for a symbol that can be present in
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// multiple object files.
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func (l *Loader) AttrDuplicateOK(i Sym) bool {
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if i < l.extStart {
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// TODO: if this path winds up being taken frequently, it
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// might make more sense to copy the flag value out of the object
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// into a larger bitmap during preload.
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r, li := l.toLocal(i)
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osym := goobj2.Sym{}
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osym.Read(r.Reader, r.SymOff(li))
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return osym.Dupok()
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}
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return l.attrDuplicateOK.has(i - l.extStart)
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}
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// SetAttrDuplicateOK sets the "duplicate OK" property for an external
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// symbol (see AttrDuplicateOK).
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func (l *Loader) SetAttrDuplicateOK(i Sym, v bool) {
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if i < l.extStart {
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panic("tried to set dupok attr on non-external symbol")
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}
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if v {
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l.attrDuplicateOK.set(i - l.extStart)
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} else {
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l.attrDuplicateOK.unset(i - l.extStart)
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}
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}
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// AttrShared returns true for symbols compiled with the -shared option.
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func (l *Loader) AttrShared(i Sym) bool {
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if i < l.extStart {
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// TODO: if this path winds up being taken frequently, it
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// might make more sense to copy the flag value out of the
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// object into a larger bitmap during preload.
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r, _ := l.toLocal(i)
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return (r.Flags() & goobj2.ObjFlagShared) != 0
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}
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return l.attrShared.has(i - l.extStart)
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}
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// SetAttrShared sets the "shared" property for an external
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// symbol (see AttrShared).
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func (l *Loader) SetAttrShared(i Sym, v bool) {
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if i < l.extStart {
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panic("tried to set shared attr on non-external symbol")
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}
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if v {
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l.attrShared.set(i - l.extStart)
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} else {
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l.attrShared.unset(i - l.extStart)
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}
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}
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// AttrExternal returns true for function symbols loaded from host
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// object files.
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func (l *Loader) AttrExternal(i Sym) bool {
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if i < l.extStart {
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return false
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}
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return l.attrExternal.has(i - l.extStart)
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}
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// SetAttrExternal sets the "external" property for an host object
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// symbol (see AttrExternal).
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func (l *Loader) SetAttrExternal(i Sym, v bool) {
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if i < l.extStart {
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panic("tried to set external attr on non-external symbol")
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}
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if v {
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l.attrExternal.set(i - l.extStart)
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} else {
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l.attrExternal.unset(i - l.extStart)
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}
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}
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// AttrTopFrame returns true for a function symbol that is an entry
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// point, meaning that unwinders should stop when they hit this
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// function.
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func (l *Loader) AttrTopFrame(i Sym) bool {
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_, ok := l.attrTopFrame[i]
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return ok
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}
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// SetAttrTopFrame sets the "top frame" property for a symbol (see
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// AttrTopFrame).
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func (l *Loader) SetAttrTopFrame(i Sym, v bool) {
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if v {
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l.attrTopFrame[i] = struct{}{}
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} else {
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delete(l.attrTopFrame, i)
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}
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}
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// AttrSpecial returns true for a symbols that do not have their
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// address (i.e. Value) computed by the usual mechanism of
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// data.go:dodata() & data.go:address().
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func (l *Loader) AttrSpecial(i Sym) bool {
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_, ok := l.attrSpecial[i]
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return ok
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}
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// SetAttrSpecial sets the "special" property for a symbol (see
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// AttrSpecial).
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func (l *Loader) SetAttrSpecial(i Sym, v bool) {
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if v {
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l.attrSpecial[i] = struct{}{}
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} else {
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delete(l.attrSpecial, i)
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}
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}
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// AttrCgoExportDynamic returns true for a symbol that has been
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// specially marked via the "cgo_export_dynamic" compiler directive
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// written by cgo (in response to //export directives in the source).
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func (l *Loader) AttrCgoExportDynamic(i Sym) bool {
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_, ok := l.attrCgoExportDynamic[i]
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return ok
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}
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// SetAttrCgoExportDynamic sets the "cgo_export_dynamic" for a symbol
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// (see AttrCgoExportDynamic).
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func (l *Loader) SetAttrCgoExportDynamic(i Sym, v bool) {
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if v {
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l.attrCgoExportDynamic[i] = struct{}{}
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} else {
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delete(l.attrCgoExportDynamic, i)
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}
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}
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// AttrCgoExportStatic returns true for a symbol that has been
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// specially marked via the "cgo_export_static" directive
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// written by cgo.
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func (l *Loader) AttrCgoExportStatic(i Sym) bool {
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_, ok := l.attrCgoExportStatic[i]
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return ok
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}
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// SetAttrCgoExportStatic sets the "cgo_export_dynamic" for a symbol
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// (see AttrCgoExportStatic).
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func (l *Loader) SetAttrCgoExportStatic(i Sym, v bool) {
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if v {
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l.attrCgoExportStatic[i] = struct{}{}
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} else {
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delete(l.attrCgoExportStatic, i)
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}
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}
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// Returns whether the i-th symbol has ReflectMethod attribute set.
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func (l *Loader) IsReflectMethod(i Sym) bool {
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return l.SymAttr(i)&goobj2.SymFlagReflectMethod != 0
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@ -688,15 +916,28 @@ func (l *Loader) SubSym(i Sym) Sym {
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return 0
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}
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// Initialize Reachable bitmap for running deadcode pass.
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// Initialize Reachable bitmap and its siblings for running deadcode pass.
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func (l *Loader) InitReachable() {
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l.growReachable(l.NSym())
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l.growAttrBitmaps(l.NSym() + 1)
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}
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// Insure that reachable bitmap has enough size.
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func (l *Loader) growReachable(reqLen int) {
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if reqLen > l.Reachable.len() {
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l.Reachable = growBitmap(reqLen, l.Reachable)
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// Insure that reachable bitmap and its siblings have enough size.
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func (l *Loader) growAttrBitmaps(reqLen int) {
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if reqLen > l.attrReachable.len() {
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// These are indexed by global symbol
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l.attrReachable = growBitmap(reqLen, l.attrReachable)
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l.attrOnList = growBitmap(reqLen, l.attrReachable)
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}
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// These are indexed by external symbol offset (e.g. i - l.extStart)
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if l.extStart == 0 {
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return
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}
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extReqLen := reqLen - int(l.extStart)
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if extReqLen > l.attrVisibilityHidden.len() {
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l.attrVisibilityHidden = growBitmap(extReqLen, l.attrVisibilityHidden)
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l.attrDuplicateOK = growBitmap(extReqLen, l.attrDuplicateOK)
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l.attrShared = growBitmap(extReqLen, l.attrShared)
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l.attrExternal = growBitmap(extReqLen, l.attrExternal)
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}
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}
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@ -933,12 +1174,12 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
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// external symbols
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for i := l.extStart; i <= l.max; i++ {
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if s := l.Syms[i]; s != nil {
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s.Attr.Set(sym.AttrReachable, l.Reachable.Has(i))
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s.Attr.Set(sym.AttrReachable, l.attrReachable.has(i))
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continue // already loaded from external object
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}
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sname := l.payloads[i-l.extStart].name
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sver := l.payloads[i-l.extStart].ver
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if l.Reachable.Has(i) || strings.HasPrefix(sname, "gofile..") { // XXX file symbols are used but not marked
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if l.attrReachable.has(i) || strings.HasPrefix(sname, "gofile..") { // XXX file symbols are used but not marked
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s := l.allocSym(sname, sver)
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pp := l.getPayload(i)
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if pp != nil {
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@ -950,7 +1191,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
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}
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}
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preprocess(arch, s)
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s.Attr.Set(sym.AttrReachable, l.Reachable.Has(i))
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s.Attr.Set(sym.AttrReachable, l.attrReachable.has(i))
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l.installSym(i, s)
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}
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}
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@ -1033,7 +1274,7 @@ func (l *Loader) installSym(i Sym, s *sym.Symbol) {
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panic("installSym nil symbol")
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}
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if l.Syms[i] != nil {
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panic("sym already present in addNewSym")
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panic("sym already present in installSym")
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}
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if l.IsExternal(i) {
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// temporary sanity check: make sure that the payload
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@ -1074,7 +1315,7 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
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// If it's been previously loaded in host object loading, we don't need to do it again.
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if s := l.Syms[istart+Sym(i)]; s != nil {
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// Mark symbol as reachable as it wasn't marked as such before.
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s.Attr.Set(sym.AttrReachable, l.Reachable.Has(istart+Sym(i)))
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s.Attr.Set(sym.AttrReachable, l.attrReachable.has(istart+Sym(i)))
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nr += r.NReloc(i)
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continue
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}
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@ -1096,7 +1337,7 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
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if t == 0 {
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log.Fatalf("missing type for %s in %s", name, r.unit.Lib)
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}
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if !l.Reachable.Has(istart+Sym(i)) && !(t == sym.SRODATA && strings.HasPrefix(name, "type.")) && name != "runtime.addmoduledata" && name != "runtime.lastmoduledatap" {
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if !l.attrReachable.has(istart+Sym(i)) && !(t == sym.SRODATA && strings.HasPrefix(name, "type.")) && name != "runtime.addmoduledata" && name != "runtime.lastmoduledatap" {
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// No need to load unreachable symbols.
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// XXX some type symbol's content may be needed in DWARF code, but they are not marked.
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// XXX reference to runtime.addmoduledata may be generated later by the linker in plugin mode.
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@ -1104,7 +1345,7 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
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}
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s := l.addNewSym(istart+Sym(i), name, ver, r.unit, t)
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s.Attr.Set(sym.AttrReachable, l.Reachable.Has(istart+Sym(i)))
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s.Attr.Set(sym.AttrReachable, l.attrReachable.has(istart+Sym(i)))
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nr += r.NReloc(i)
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}
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return nr
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@ -1233,7 +1474,7 @@ func loadObjFull(l *Loader, r *oReader) {
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dupok := osym.Dupok()
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if dupok {
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if dupsym := l.symsByName[ver][name]; dupsym != istart+Sym(i) {
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if l.Reachable.Has(dupsym) {
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if l.attrReachable.has(dupsym) {
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// A dupok symbol is resolved to another package. We still need
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// to record its presence in the current package, as the trampoline
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// pass expects packages are laid out in dependency order.
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@ -1275,14 +1516,14 @@ func loadObjFull(l *Loader, r *oReader) {
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sz := r.Size
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rt := r.Type
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if rt == objabi.R_METHODOFF {
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if l.Reachable.Has(rs) {
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if l.attrReachable.has(rs) {
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rt = objabi.R_ADDROFF
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} else {
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sz = 0
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rs = 0
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}
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}
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if rt == objabi.R_WEAKADDROFF && !l.Reachable.Has(rs) {
|
||||
if rt == objabi.R_WEAKADDROFF && !l.attrReachable.has(rs) {
|
||||
rs = 0
|
||||
sz = 0
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue