return i
}
// symbol already exists
+ // Fix for issue #47185 -- given two dupok or BSS symbols with
+ // different sizes, favor symbol with larger size. See also
+ // issue #46653 and #72032.
+ oldsz := l.SymSize(oldi)
+ sz := int64(r.Sym(li).Siz())
if osym.Dupok() {
if l.flags&FlagStrictDups != 0 {
l.checkdup(name, r, li, oldi)
}
- // Fix for issue #47185 -- given two dupok symbols with
- // different sizes, favor symbol with larger size. See
- // also issue #46653.
- szdup := l.SymSize(oldi)
- sz := int64(r.Sym(li).Siz())
- if szdup < sz {
+ if oldsz < sz {
// new symbol overwrites old symbol.
l.objSyms[oldi] = objSym{r.objidx, li}
}
if oldsym.Dupok() {
return oldi
}
- overwrite := r.DataSize(li) != 0
+ // If one is a DATA symbol (i.e. has content, DataSize != 0)
+ // and the other is BSS, the one with content wins.
+ // If both are BSS, the one with larger size wins.
+ // Specifically, the "overwrite" variable and the final result are
+ //
+ // new sym old sym overwrite
+ // ---------------------------------------------
+ // DATA DATA true => ERROR
+ // DATA lg/eq BSS sm/eq true => new wins
+ // DATA small BSS large true => ERROR
+ // BSS large DATA small true => ERROR
+ // BSS large BSS small true => new wins
+ // BSS sm/eq D/B lg/eq false => old wins
+ overwrite := r.DataSize(li) != 0 || oldsz < sz
if overwrite {
// new symbol overwrites old symbol.
oldtyp := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
- if !(oldtyp.IsData() && oldr.DataSize(oldli) == 0) {
+ if !(oldtyp.IsData() && oldr.DataSize(oldli) == 0) || oldsz > sz {
log.Fatalf("duplicated definition of symbol %s, from %s and %s", name, r.unit.Lib.Pkg, oldr.unit.Lib.Pkg)
}
l.objSyms[oldi] = objSym{r.objidx, li}
"testing"
imacho "cmd/internal/macho"
+ "cmd/internal/objfile"
"cmd/internal/sys"
)
})
}
}
+
+func TestLinknameBSS(t *testing.T) {
+ // Test that the linker chooses the right one as the definition
+ // for linknamed variables. See issue #72032.
+ testenv.MustHaveGoBuild(t)
+ t.Parallel()
+
+ tmpdir := t.TempDir()
+
+ src := filepath.Join("testdata", "linkname", "sched.go")
+ exe := filepath.Join(tmpdir, "sched.exe")
+ cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-o", exe, src)
+ out, err := cmd.CombinedOutput()
+ if err != nil {
+ t.Fatalf("build failed unexpectedly: %v:\n%s", err, out)
+ }
+
+ // Check the symbol size.
+ f, err := objfile.Open(exe)
+ if err != nil {
+ t.Fatalf("fail to open executable: %v", err)
+ }
+ defer f.Close()
+ syms, err := f.Symbols()
+ if err != nil {
+ t.Fatalf("fail to get symbols: %v", err)
+ }
+ found := false
+ for _, s := range syms {
+ if s.Name == "runtime.sched" || s.Name == "_runtime.sched" {
+ found = true
+ if s.Size < 100 {
+ // As of Go 1.25 (Mar 2025), runtime.sched has 6848 bytes on
+ // darwin/arm64. It should always be larger than 100 bytes on
+ // all platforms.
+ t.Errorf("runtime.sched symbol size too small: want > 100, got %d", s.Size)
+ }
+ }
+ }
+ if !found {
+ t.Errorf("runtime.sched symbol not found")
+ }
+
+ // Executable should run.
+ cmd = testenv.Command(t, exe)
+ out, err = cmd.CombinedOutput()
+ if err != nil {
+ t.Errorf("executable failed to run: %v\n%s", err, out)
+ }
+}