Correctness: floating point equality using bits instead of ==.

Special values for float and double make it inaccurate to test the equality with ==.
The main Java library uses the standard Object.equals() implementation for all fields,
which for floating point fields means Float.equals() or Double.equals(). They define
equality as bitwise equality, with all NaN representations normalized to the same bit
sequence (and therefore equal to each other). This test checks that the nano
implementation complies with Object.equals(), so NaN == NaN and +0.0 != -0.0.

Change-Id: I97bb4a3687223d8a212c70cd736436b9dd80c1d7

3 files changed, 62 insertions, 40 deletions

diff --git a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
index b6c98b4..9898aaf 100644
--- a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
@@ -175,38 +175,6 @@ int FixedSize(FieldDescriptor::Type type) {
   return -1;
 }
 
-// Returns true if the field has a default value equal to NaN.
-bool IsDefaultNaN(const FieldDescriptor* field) {
-  switch (field->type()) {
-    case FieldDescriptor::TYPE_INT32   : return false;
-    case FieldDescriptor::TYPE_UINT32  : return false;
-    case FieldDescriptor::TYPE_SINT32  : return false;
-    case FieldDescriptor::TYPE_FIXED32 : return false;
-    case FieldDescriptor::TYPE_SFIXED32: return false;
-    case FieldDescriptor::TYPE_INT64   : return false;
-    case FieldDescriptor::TYPE_UINT64  : return false;
-    case FieldDescriptor::TYPE_SINT64  : return false;
-    case FieldDescriptor::TYPE_FIXED64 : return false;
-    case FieldDescriptor::TYPE_SFIXED64: return false;
-    case FieldDescriptor::TYPE_FLOAT   :
-      return isnan(field->default_value_float());
-    case FieldDescriptor::TYPE_DOUBLE  :
-      return isnan(field->default_value_double());
-    case FieldDescriptor::TYPE_BOOL    : return false;
-    case FieldDescriptor::TYPE_STRING  : return false;
-    case FieldDescriptor::TYPE_BYTES   : return false;
-    case FieldDescriptor::TYPE_ENUM    : return false;
-    case FieldDescriptor::TYPE_GROUP   : return false;
-    case FieldDescriptor::TYPE_MESSAGE : return false;
-
-    // No default because we want the compiler to complain if any new
-    // types are added.
-  }
-
-  GOOGLE_LOG(FATAL) << "Can't get here.";
-  return false;
-}
-
 // Return true if the type is a that has variable length
 // for instance String's.
 bool IsVariableLenType(JavaType type) {
@@ -384,15 +352,21 @@ GenerateSerializationConditional(io::Printer* printer) const {
     printer->Print(variables_,
       "if (");
   }
-  if (IsArrayType(GetJavaType(descriptor_))) {
+  JavaType java_type = GetJavaType(descriptor_);
+  if (IsArrayType(java_type)) {
     printer->Print(variables_,
       "!java.util.Arrays.equals(this.$name$, $default$)) {\n");
-  } else if (IsReferenceType(GetJavaType(descriptor_))) {
+  } else if (IsReferenceType(java_type)) {
     printer->Print(variables_,
       "!this.$name$.equals($default$)) {\n");
-  } else if (IsDefaultNaN(descriptor_)) {
+  } else if (java_type == JAVATYPE_FLOAT) {
     printer->Print(variables_,
-      "!$capitalized_type$.isNaN(this.$name$)) {\n");
+      "java.lang.Float.floatToIntBits(this.$name$)\n"
+      "    != java.lang.Float.floatToIntBits($default$)) {\n");
+  } else if (java_type == JAVATYPE_DOUBLE) {
+    printer->Print(variables_,
+      "java.lang.Double.doubleToLongBits(this.$name$)\n"
+      "    != java.lang.Double.doubleToLongBits($default$)) {\n");
   } else {
     printer->Print(variables_,
       "this.$name$ != $default$) {\n");
@@ -464,6 +438,36 @@ GenerateEqualsCode(io::Printer* printer) const {
     printer->Print(") {\n"
       "  return false;\n"
       "}\n");
+  } else if (java_type == JAVATYPE_FLOAT) {
+    printer->Print(variables_,
+      "{\n"
+      "  int bits = java.lang.Float.floatToIntBits(this.$name$);\n"
+      "  if (bits != java.lang.Float.floatToIntBits(other.$name$)");
+    if (params_.generate_has()) {
+      printer->Print(variables_,
+        "\n"
+        "      || (bits == java.lang.Float.floatToIntBits($default$)\n"
+        "          && this.has$capitalized_name$ != other.has$capitalized_name$)");
+    }
+    printer->Print(") {\n"
+      "    return false;\n"
+      "  }\n"
+      "}\n");
+  } else if (java_type == JAVATYPE_DOUBLE) {
+    printer->Print(variables_,
+      "{\n"
+      "  long bits = java.lang.Double.doubleToLongBits(this.$name$);\n"
+      "  if (bits != java.lang.Double.doubleToLongBits(other.$name$)");
+    if (params_.generate_has()) {
+      printer->Print(variables_,
+        "\n"
+        "      || (bits == java.lang.Double.doubleToLongBits($default$)\n"
+        "          && this.has$capitalized_name$ != other.has$capitalized_name$)");
+    }
+    printer->Print(") {\n"
+      "    return false;\n"
+      "  }\n"
+      "}\n");
   } else {
     printer->Print(variables_,
       "if (this.$name$ != other.$name$");
@@ -623,12 +627,26 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
 void AccessorPrimitiveFieldGenerator::
 GenerateEqualsCode(io::Printer* printer) const {
   switch (GetJavaType(descriptor_)) {
-    // For all Java primitive types below, the hash codes match the
-    // results of BoxedType.valueOf(primitiveValue).hashCode().
-    case JAVATYPE_INT:
-    case JAVATYPE_LONG:
+    // For all Java primitive types below, the equality checks match the
+    // results of BoxedType.valueOf(primitiveValue).equals(otherValue).
     case JAVATYPE_FLOAT:
+      printer->Print(variables_,
+        "if ($different_has$\n"
+        "    || java.lang.Float.floatToIntBits($name$_)\n"
+        "        != java.lang.Float.floatToIntBits(other.$name$_)) {\n"
+        "  return false;\n"
+        "}\n");
+      break;
     case JAVATYPE_DOUBLE:
+      printer->Print(variables_,
+        "if ($different_has$\n"
+        "    || java.lang.Double.doubleToLongBits($name$_)\n"
+        "        != java.lang.Double.doubleToLongBits(other.$name$_)) {\n"
+        "  return false;\n"
+        "}\n");
+      break;
+    case JAVATYPE_INT:
+    case JAVATYPE_LONG:
     case JAVATYPE_BOOLEAN:
       printer->Print(variables_,
         "if ($different_has$\n"
diff --git a/src/google/protobuf/unittest_accessors_nano.proto b/src/google/protobuf/unittest_accessors_nano.proto
index 875af25..f1d4d34 100644
--- a/src/google/protobuf/unittest_accessors_nano.proto
+++ b/src/google/protobuf/unittest_accessors_nano.proto
@@ -49,6 +49,8 @@ message TestNanoAccessors {
 
   // Singular
   optional int32  optional_int32    =  1;
+  optional float  optional_float    = 11;
+  optional double optional_double   = 12;
   optional string optional_string   = 14;
   optional bytes  optional_bytes    = 15;
 
diff --git a/src/google/protobuf/unittest_has_nano.proto b/src/google/protobuf/unittest_has_nano.proto
index 61800f2..289d08a 100644
--- a/src/google/protobuf/unittest_has_nano.proto
+++ b/src/google/protobuf/unittest_has_nano.proto
@@ -49,6 +49,8 @@ message TestAllTypesNanoHas {
 
   // Singular
   optional int32  optional_int32    =  1;
+  optional float  optional_float    = 11;
+  optional double optional_double   = 12;
   optional string optional_string   = 14;
   optional bytes  optional_bytes    = 15;