cmd/compile: don't instrument counter globals in internal/fuzz

Fixes: #72766

Change-Id: I45b521e53c2a11e259dc99e2dfc8e40cac39139a
Reviewed-on: https://go-review.googlesource.com/c/go/+/673575
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/cgo/internal/testsanitizers/asan_test.go

@@ -135,6 +135,9 @@ func TestASANFuzz(t *testing.T) {
 	if bytes.Contains(out, []byte("AddressSanitizer")) {
 		t.Error(`output contains "AddressSanitizer", but should not`)
 	}
+	if !bytes.Contains(out, []byte("FUZZ FAILED")) {
+		t.Error(`fuzz test did not fail with a "FUZZ FAILED" sentinel error`)
+	}
 }
 
 func mustHaveASAN(t *testing.T) *config {

src/cmd/cgo/internal/testsanitizers/testdata/asan_fuzz_test.go

@@ -24,7 +24,7 @@ func FuzzReverse(f *testing.F) {
 		r1 := Reverse(s)
 		r2 := Reverse(r1)
 		if s != r2 {
-			t.Errorf("got %q want %q", r2, s)
+			t.Errorf("FUZZ FAILED: got %q want %q", r2, s)
 		}
 	})
 }

src/cmd/compile/internal/pkginit/initAsanGlobals.go

@@ -227,6 +227,12 @@ func canInstrumentGlobal(g ir.Node) bool {
 		return false
 	}
 
+	// Do not instrument counter globals in internal/fuzz. These globals are replaced by the linker.
+	// See go.dev/issue/72766 for more details.
+	if n.Sym().Pkg.Path == "internal/fuzz" && (n.Sym().Name == "_counters" || n.Sym().Name == "_ecounters") {
+		return false
+	}
+
 	// Do not instrument globals that are linknamed, because their home package will do the work.
 	if n.Sym().Linkname != "" {
 		return false