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cmd/link: improved host archive debug trace output

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When ctxt.Debugvlog > 1, produce additional trace output to describe
which object files are being pulled out of host archive libraries and
why they were pulled (e.g. which symbol had a reference to something
in a library). Intended to make it easier to debug problems with cgo
internal linking.

Change-Id: Icd64aff244b9145162a00cb51642ef32f26adfba
Reviewed-on: https://go-review.googlesource.com/c/go/+/451736
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Than McIntosh 2022-11-01 10:27:18 -04:00
parent 58a2db181b
commit 8205d83fe2
3 changed files with 32 additions and 15 deletions
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11
src/cmd/link/internal/ld/ar.go
View file

@ -110,12 +110,15 @@ func hostArchive(ctxt *Link, name string) {
for any {
var load []uint64
returnAllUndefs := -1
undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
for _, symIdx := range undefs {
name := ctxt.loader.SymName(symIdx)
if off := armap[name]; off != 0 && !loaded[off] {
undefs, froms := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
for k, symIdx := range undefs {
sname := ctxt.loader.SymName(symIdx)
if off := armap[sname]; off != 0 && !loaded[off] {
load = append(load, off)
loaded[off] = true
if ctxt.Debugvlog > 1 {
ctxt.Logf("hostArchive(%s): selecting object at offset %x to resolve %s [%d] reference from %s [%d]\n", name, off, sname, symIdx, ctxt.loader.SymName(froms[k]), froms[k])
}
}
}

16
src/cmd/link/internal/ld/lib.go
View file

@ -615,9 +615,14 @@ func (ctxt *Link) loadlib() {
// If we have any undefined symbols in external
// objects, try to read them from the libgcc file.
any := false
undefs := ctxt.loader.UndefinedRelocTargets(1)
undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
if ctxt.Debugvlog > 1 {
ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
ctxt.loader.SymName(undefs[0]), undefs[0],
ctxt.loader.SymName(froms[0]), froms[0])
}
}
if any {
if *flagLibGCC == "" {
@ -681,9 +686,14 @@ func loadWindowsHostArchives(ctxt *Link) {
hostArchive(ctxt, p)
}
any = false
undefs := ctxt.loader.UndefinedRelocTargets(1)
undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
if len(undefs) > 0 {
any = true
if ctxt.Debugvlog > 1 {
ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
ctxt.loader.SymName(undefs[0]), undefs[0],
ctxt.loader.SymName(froms[0]), froms[0])
}
}
}
// If needed, create the __CTOR_LIST__ and __DTOR_LIST__
@ -2141,7 +2151,7 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
// to true if there is an unresolved reference to the symbol in want[K].
func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
returnAllUndefs := -1
undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
seen := make(map[loader.Sym]struct{})
rval := make([]bool, len(want))
wantm := make(map[string]int)

20
src/cmd/link/internal/loader/loader.go
View file

@ -2392,12 +2392,15 @@ func (l *Loader) RelocVariant(s Sym, ri int) sym.RelocVariant {
// space, looking for symbols with relocations targeting undefined
// references. The linker's loadlib method uses this to determine if
// there are unresolved references to functions in system libraries
// (for example, libgcc.a), presumably due to CGO code. Return
// value is a list of loader.Sym's corresponding to the undefined
// cross-refs. The "limit" param controls the maximum number of
// results returned; if "limit" is -1, then all undefs are returned.
func (l *Loader) UndefinedRelocTargets(limit int) []Sym {
result := []Sym{}
// (for example, libgcc.a), presumably due to CGO code. Return value
// is a pair of lists of loader.Sym's. First list corresponds to the
// corresponding to the undefined symbols themselves, the second list
// is the symbol that is making a reference to the undef. The "limit"
// param controls the maximum number of results returned; if "limit"
// is -1, then all undefs are returned.
func (l *Loader) UndefinedRelocTargets(limit int) ([]Sym, []Sym) {
result, fromr := []Sym{}, []Sym{}
outerloop:
for si := Sym(1); si < Sym(len(l.objSyms)); si++ {
relocs := l.Relocs(si)
for ri := 0; ri < relocs.Count(); ri++ {
@ -2405,13 +2408,14 @@ func (l *Loader) UndefinedRelocTargets(limit int) []Sym {
rs := r.Sym()
if rs != 0 && l.SymType(rs) == sym.SXREF && l.SymName(rs) != ".got" {
result = append(result, rs)
fromr = append(fromr, si)
if limit != -1 && len(result) >= limit {
break
break outerloop
}
}
}
}
return result
return result, fromr
}
// AssignTextSymbolOrder populates the Textp slices within each