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cmd/link: fix confusing error on unresolved symbol
Currently, if an assembly file includes a static reference to an undefined symbol, and another package also has an undefined reference to that symbol, the linker can report an error like: x: relocation target zero not defined for ABI0 (but is defined for ABI0) Since the symbol is referenced in another package, the code in ErrorUnresolved that looks for alternative ABI symbols finds that symbol in the symbol table, but doesn't check that it's actually defined, which is where the "but is defined for ABI0" comes from. The "not defined for ABI0" is because ErrorUnresolved failed to turn the static symbol's version back into an ABI, and it happened to print the zero value for an ABI. This CL fixes both of these problems. It explicitly maps the relocation version back to an ABI and detects if it can't be mapped back (e.g., because it's a static reference). Then, if it finds a symbol with a different ABI in the symbol table, it checks to make sure it's a definition, and not simply an unresolved reference. Fixes #29852. Change-Id: Ice45cc41c1907919ce5750f74588e8047eaa888c Reviewed-on: https://go-review.googlesource.com/c/159518 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
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@ -113,15 +113,16 @@ func (ctxt *Link) ErrorUnresolved(s *sym.Symbol, r *sym.Reloc) {
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// Try to find symbol under another ABI.
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var reqABI, haveABI obj.ABI
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haveABI = ^obj.ABI(0)
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for abi := obj.ABI(0); abi < obj.ABICount; abi++ {
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v := sym.ABIToVersion(abi)
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if v == -1 {
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continue
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}
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if v == int(r.Sym.Version) {
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reqABI = abi
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} else if ctxt.Syms.ROLookup(r.Sym.Name, v) != nil {
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haveABI = abi
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reqABI, ok := sym.VersionToABI(int(r.Sym.Version))
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if ok {
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for abi := obj.ABI(0); abi < obj.ABICount; abi++ {
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v := sym.ABIToVersion(abi)
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if v == -1 {
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continue
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}
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if rs := ctxt.Syms.ROLookup(r.Sym.Name, v); rs != nil && rs.Type != sym.Sxxx {
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haveABI = abi
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}
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}
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}
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@ -68,6 +68,16 @@ func ABIToVersion(abi obj.ABI) int {
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return -1
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}
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func VersionToABI(v int) (obj.ABI, bool) {
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switch v {
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case SymVerABI0:
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return obj.ABI0, true
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case SymVerABIInternal:
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return obj.ABIInternal, true
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}
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return ^obj.ABI(0), false
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}
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func (s *Symbol) String() string {
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if s.Version == 0 {
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return s.Name
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@ -6,6 +6,7 @@ import (
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"os"
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"os/exec"
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"path/filepath"
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"regexp"
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"strings"
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"testing"
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)
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@ -116,3 +117,57 @@ func TestIssue28429(t *testing.T) {
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// to compile the extra section.
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runGo("tool", "link", "main.a")
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}
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func TestUnresolved(t *testing.T) {
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testenv.MustHaveGoBuild(t)
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tmpdir, err := ioutil.TempDir("", "unresolved-")
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if err != nil {
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t.Fatalf("failed to create temp dir: %v", err)
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}
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defer os.RemoveAll(tmpdir)
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write := func(name, content string) {
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err := ioutil.WriteFile(filepath.Join(tmpdir, name), []byte(content), 0666)
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if err != nil {
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t.Fatal(err)
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}
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}
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// Test various undefined references. Because of issue #29852,
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// this used to give confusing error messages because the
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// linker would find an undefined reference to "zero" created
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// by the runtime package.
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write("main.go", `package main
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func main() {
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x()
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}
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func x()
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`)
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write("main.s", `
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TEXT ·x(SB),0,$0
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MOVD zero<>(SB), AX
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MOVD zero(SB), AX
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MOVD ·zero(SB), AX
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RET
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`)
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cmd := exec.Command(testenv.GoToolPath(t), "build")
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cmd.Dir = tmpdir
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cmd.Env = append(os.Environ(), []string{"GOARCH=amd64", "GOOS=linux"}...)
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out, err := cmd.CombinedOutput()
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if err == nil {
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t.Fatalf("expected build to fail, but it succeeded")
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}
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out = regexp.MustCompile("(?m)^#.*\n").ReplaceAll(out, nil)
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got := string(out)
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want := `main.x: relocation target zero not defined
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main.x: relocation target zero not defined
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main.x: relocation target main.zero not defined
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`
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if want != got {
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t.Fatalf("want:\n%sgot:\n%s", want, got)
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}
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}
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