reflect, runtime: check equality, not identity, for method names

When dynamically linking Go code, it is no longer safe to assume that
strings that end up in method names are identical if they are equal.

The performance impact seems to be noise:

benchmark                    old ns/op     new ns/op     delta
BenchmarkAssertI2E2          13.3          13.1          -1.50%
BenchmarkAssertE2I           23.5          23.2          -1.28%
BenchmarkAssertE2E2Blank     0.83          0.82          -1.20%
BenchmarkConvT2ISmall        60.7          60.1          -0.99%
BenchmarkAssertI2T           10.2          10.1          -0.98%
BenchmarkAssertE2T           10.2          10.3          +0.98%
BenchmarkConvT2ESmall        56.7          57.2          +0.88%
BenchmarkConvT2ILarge        59.4          58.9          -0.84%
BenchmarkConvI2E             13.0          12.9          -0.77%
BenchmarkAssertI2E           13.4          13.3          -0.75%
BenchmarkConvT2IUintptr      57.9          58.3          +0.69%
BenchmarkConvT2ELarge        55.9          55.6          -0.54%
BenchmarkAssertI2I           23.8          23.7          -0.42%
BenchmarkConvT2EUintptr      55.4          55.5          +0.18%
BenchmarkAssertE2E           6.12          6.11          -0.16%
BenchmarkAssertE2E2          14.4          14.4          +0.00%
BenchmarkAssertE2T2          10.0          10.0          +0.00%
BenchmarkAssertE2T2Blank     0.83          0.83          +0.00%
BenchmarkAssertE2TLarge      10.7          10.7          +0.00%
BenchmarkAssertI2E2Blank     0.83          0.83          +0.00%
BenchmarkConvI2I             23.4          23.4          +0.00%

Change-Id: I0b3dfc314215a4d4e09eec6b42c1e3ebce33eb56
Reviewed-on: https://go-review.googlesource.com/8239Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/reflect/type.go

@@ -1150,7 +1150,7 @@ func implements(T, V *rtype) bool {
 		for j := 0; j < len(v.methods); j++ {
 			tm := &t.methods[i]
 			vm := &v.methods[j]
-			if vm.name == tm.name && vm.pkgPath == tm.pkgPath && vm.typ == tm.typ {
+			if *vm.name == *tm.name && vm.pkgPath == tm.pkgPath && vm.typ == tm.typ {
 				if i++; i >= len(t.methods) {
 					return true
 				}
@@ -1167,7 +1167,7 @@ func implements(T, V *rtype) bool {
 	for j := 0; j < len(v.methods); j++ {
 		tm := &t.methods[i]
 		vm := &v.methods[j]
-		if vm.name == tm.name && vm.pkgPath == tm.pkgPath && vm.mtyp == tm.typ {
+		if *vm.name == *tm.name && vm.pkgPath == tm.pkgPath && vm.mtyp == tm.typ {
 			if i++; i >= len(t.methods) {
 				return true
 			}

src/runtime/iface.go

@@ -94,7 +94,7 @@ search:
 		itype := i._type
 		for ; j < nt; j++ {
 			t := &x.mhdr[j]
-			if t.mtyp == itype && t.name == iname && t.pkgpath == ipkgpath {
+			if t.mtyp == itype && (t.name == iname || *t.name == *iname) && t.pkgpath == ipkgpath {
 				if m != nil {
 					*(*unsafe.Pointer)(add(unsafe.Pointer(&m.fun[0]), uintptr(k)*ptrSize)) = t.ifn
 				}